14 Aug, 2018
1 commit
-
Pull scheduler updates from Thomas Gleixner:
- Cleanup and improvement of NUMA balancing
- Refactoring and improvements to the PELT (Per Entity Load Tracking)
code- Watchdog simplification and related cleanups
- The usual pile of small incremental fixes and improvements
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (41 commits)
watchdog: Reduce message verbosity
stop_machine: Reflow cpu_stop_queue_two_works()
sched/numa: Move task_numa_placement() closer to numa_migrate_preferred()
sched/numa: Use group_weights to identify if migration degrades locality
sched/numa: Update the scan period without holding the numa_group lock
sched/numa: Remove numa_has_capacity()
sched/numa: Modify migrate_swap() to accept additional parameters
sched/numa: Remove unused task_capacity from 'struct numa_stats'
sched/numa: Skip nodes that are at 'hoplimit'
sched/debug: Reverse the order of printing faults
sched/numa: Use task faults only if numa_group is not yet set up
sched/numa: Set preferred_node based on best_cpu
sched/numa: Simplify load_too_imbalanced()
sched/numa: Evaluate move once per node
sched/numa: Remove redundant field
sched/debug: Show the sum wait time of a task group
sched/fair: Remove #ifdefs from scale_rt_capacity()
sched/core: Remove get_cpu() from sched_fork()
sched/cpufreq: Clarify sugov_get_util()
sched/sysctl: Remove unused sched_time_avg_ms sysctl
...
26 Jul, 2018
1 commit
-
There is a window for racing when printing directly to task->comm,
allowing other threads to see a non-terminated string. The vsnprintf
function fills the buffer, counts the truncated chars, then finally
writes the \0 at the end.creator other
vsnprintf:
fill (not terminated)
count the rest trace_sched_waking(p):
... memcpy(comm, p->comm, TASK_COMM_LEN)
write \0The consequences depend on how 'other' uses the string. In our case,
it was copied into the tracing system's saved cmdlines, a buffer of
adjacent TASK_COMM_LEN-byte buffers (note the 'n' where 0 should be):crash-arm64> x/1024s savedcmd->saved_cmdlines | grep 'evenk'
0xffffffd5b3818640: "irq/497-pwr_evenkworker/u16:12"...and a strcpy out of there would cause stack corruption:
[224761.522292] Kernel panic - not syncing: stack-protector:
Kernel stack is corrupted in: ffffff9bf9783c78crash-arm64> kbt | grep 'comm\|trace_print_context'
#6 0xffffff9bf9783c78 in trace_print_context+0x18c(+396)
comm (char [16]) = "irq/497-pwr_even"crash-arm64> rd 0xffffffd4d0e17d14 8
ffffffd4d0e17d14: 2f71726900000000 5f7277702d373934 ....irq/497-pwr_
ffffffd4d0e17d24: 726f776b6e657665 3a3631752f72656b evenkworker/u16:
ffffffd4d0e17d34: f9780248ff003231 cede60e0ffffff9b 12..H.x......`..
ffffffd4d0e17d44: cede60c8ffffffd4 00000fffffffffd4 .....`..........The workaround in e09e28671 (use strlcpy in __trace_find_cmdline) was
likely needed because of this same bug.Solved by vsnprintf:ing to a local buffer, then using set_task_comm().
This way, there won't be a window where comm is not terminated.Link: http://lkml.kernel.org/r/20180726071539.188015-1-snild@sony.com
Cc: stable@vger.kernel.org
Fixes: bc0c38d139ec7 ("ftrace: latency tracer infrastructure")
Reviewed-by: Steven Rostedt (VMware)
Signed-off-by: Snild Dolkow
Signed-off-by: Steven Rostedt (VMware)
03 Jul, 2018
2 commits
-
Oleg explains the reason we could hit park+park is that
smpboot_update_cpumask_percpu_thread()'sfor_each_cpu_and(cpu, &tmp, cpu_online_mask)
smpboot_park_kthread();turns into:
for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask, (void)and)
smpboot_park_kthread();on UP, ignoring the mask. But since we just completely removed that
function, this is no longer relevant.So revert commit:
b1f5b378e126 ("kthread: Allow kthread_park() on a parked kthread")
Suggested-by: Oleg Nesterov
Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar -
Gaurav reports that commit:
85f1abe0019f ("kthread, sched/wait: Fix kthread_parkme() completion issue")
isn't working for him. Because of the following race:
> controller Thread CPUHP Thread
> takedown_cpu
> kthread_park
> kthread_parkme
> Set KTHREAD_SHOULD_PARK
> smpboot_thread_fn
> set Task interruptible
>
>
> wake_up_process
> if (!(p->state & state))
> goto out;
>
> Kthread_parkme
> SET TASK_PARKED
> schedule
> raw_spin_lock(&rq->lock)
> ttwu_remote
> waiting for __task_rq_lock
> context_switch
>
> finish_lock_switch
>
>
>
> Case TASK_PARKED
> kthread_park_complete
>
>
> SET RunningFurthermore, Oleg noticed that the whole scheduler TASK_PARKED
handling is buggered because the TASK_DEAD thing is done with
preemption disabled, the current code can still complete early on
preemption :/So basically revert that earlier fix and go with a variant of the
alternative mentioned in the commit. Promote TASK_PARKED to special
state to avoid the store-store issue on task->state leading to the
WARN in kthread_unpark() -> __kthread_bind().But in addition, add wait_task_inactive() to kthread_park() to ensure
the task really is PARKED when we return from kthread_park(). This
avoids the whole kthread still gets migrated nonsense -- although it
would be really good to get this done differently.Reported-by: Gaurav Kohli
Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Oleg Nesterov
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Fixes: 85f1abe0019f ("kthread, sched/wait: Fix kthread_parkme() completion issue")
Signed-off-by: Ingo Molnar
25 May, 2018
1 commit
-
The following commit:
85f1abe0019f ("kthread, sched/wait: Fix kthread_parkme() completion issue")
added a WARN() in the case where we call kthread_park() on an already
parked thread, because the old code wasn't doing the right thing there
and it wasn't at all clear that would happen.It turns out, this does in fact happen, so we have to deal with it.
Instead of potentially returning early, also wait for the completion.
This does however mean we have to use complete_all() and re-initialize
the completion on re-use.Reported-by: LKP
Tested-by: Meelis Roos
Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: kernel test robot
Cc: wfg@linux.intel.com
Cc: Thomas Gleixner
Fixes: 85f1abe0019f ("kthread, sched/wait: Fix kthread_parkme() completion issue")
Link: http://lkml.kernel.org/r/20180504091142.GI12235@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar
03 May, 2018
2 commits
-
Even with the wait-loop fixed, there is a further issue with
kthread_parkme(). Upon hotplug, when we do takedown_cpu(),
smpboot_park_threads() can return before all those threads are in fact
blocked, due to the placement of the complete() in __kthread_parkme().When that happens, sched_cpu_dying() -> migrate_tasks() can end up
migrating such a still runnable task onto another CPU.Normally the task will have hit schedule() and gone to sleep by the
time we do kthread_unpark(), which will then do __kthread_bind() to
re-bind the task to the correct CPU.However, when we loose the initial TASK_PARKED store to the concurrent
wakeup issue described previously, do the complete(), get migrated, it
is possible to either:- observe kthread_unpark()'s clearing of SHOULD_PARK and terminate
the park and set TASK_RUNNING, or- __kthread_bind()'s wait_task_inactive() to observe the competing
TASK_RUNNING store.Either way the WARN() in __kthread_bind() will trigger and fail to
correctly set the CPU affinity.Fix this by only issuing the complete() when the kthread has scheduled
out. This does away with all the icky 'still running' nonsense.The alternative is to promote TASK_PARKED to a special state, this
guarantees wait_task_inactive() cannot observe a 'stale' TASK_RUNNING
and we'll end up doing the right thing, but this preserves the whole
icky business of potentially migating the still runnable thing.Reported-by: Gaurav Kohli
Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Oleg Nesterov
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
Gaurav reported a problem with __kthread_parkme() where a concurrent
try_to_wake_up() could result in competing stores to ->state which,
when the TASK_PARKED store got lost bad things would happen.The comment near set_current_state() actually mentions this competing
store, but only mentions the case against TASK_RUNNING. This same
store, with different timing, can happen against a subsequent !RUNNING
store.This normally is not a problem, because as per that same comment, the
!RUNNING state store is inside a condition based wait-loop:for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (!need_sleep)
break;
schedule();
}
__set_current_state(TASK_RUNNING);If we loose the (first) TASK_UNINTERRUPTIBLE store to a previous
(concurrent) wakeup, the schedule() will NO-OP and we'll go around the
loop once more.The problem here is that the TASK_PARKED store is not inside the
KTHREAD_SHOULD_PARK condition wait-loop.There is a genuine issue with sleeps that do not have a condition;
this is addressed in a subsequent patch.Reported-by: Gaurav Kohli
Signed-off-by: Peter Zijlstra (Intel)
Reviewed-by: Oleg Nesterov
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar
22 Nov, 2017
1 commit
-
With all callbacks converted, and the timer callback prototype
switched over, the TIMER_FUNC_TYPE cast is no longer needed,
so remove it. Conversion was done with the following scripts:perl -pi -e 's|\(TIMER_FUNC_TYPE\)||g' \
$(git grep TIMER_FUNC_TYPE | cut -d: -f1 | sort -u)perl -pi -e 's|\(TIMER_DATA_TYPE\)||g' \
$(git grep TIMER_DATA_TYPE | cut -d: -f1 | sort -u)The now unused macros are also dropped from include/linux/timer.h.
Signed-off-by: Kees Cook
15 Nov, 2017
1 commit
-
Pull core block layer updates from Jens Axboe:
"This is the main pull request for block storage for 4.15-rc1.Nothing out of the ordinary in here, and no API changes or anything
like that. Just various new features for drivers, core changes, etc.
In particular, this pull request contains:- A patch series from Bart, closing the whole on blk/scsi-mq queue
quescing.- A series from Christoph, building towards hidden gendisks (for
multipath) and ability to move bio chains around.- NVMe
- Support for native multipath for NVMe (Christoph).
- Userspace notifications for AENs (Keith).
- Command side-effects support (Keith).
- SGL support (Chaitanya Kulkarni)
- FC fixes and improvements (James Smart)
- Lots of fixes and tweaks (Various)- bcache
- New maintainer (Michael Lyle)
- Writeback control improvements (Michael)
- Various fixes (Coly, Elena, Eric, Liang, et al)- lightnvm updates, mostly centered around the pblk interface
(Javier, Hans, and Rakesh).- Removal of unused bio/bvec kmap atomic interfaces (me, Christoph)
- Writeback series that fix the much discussed hundreds of millions
of sync-all units. This goes all the way, as discussed previously
(me).- Fix for missing wakeup on writeback timer adjustments (Yafang
Shao).- Fix laptop mode on blk-mq (me).
- {mq,name} tupple lookup for IO schedulers, allowing us to have
alias names. This means you can use 'deadline' on both !mq and on
mq (where it's called mq-deadline). (me).- blktrace race fix, oopsing on sg load (me).
- blk-mq optimizations (me).
- Obscure waitqueue race fix for kyber (Omar).
- NBD fixes (Josef).
- Disable writeback throttling by default on bfq, like we do on cfq
(Luca Miccio).- Series from Ming that enable us to treat flush requests on blk-mq
like any other request. This is a really nice cleanup.- Series from Ming that improves merging on blk-mq with schedulers,
getting us closer to flipping the switch on scsi-mq again.- BFQ updates (Paolo).
- blk-mq atomic flags memory ordering fixes (Peter Z).
- Loop cgroup support (Shaohua).
- Lots of minor fixes from lots of different folks, both for core and
driver code"* 'for-4.15/block' of git://git.kernel.dk/linux-block: (294 commits)
nvme: fix visibility of "uuid" ns attribute
blk-mq: fixup some comment typos and lengths
ide: ide-atapi: fix compile error with defining macro DEBUG
blk-mq: improve tag waiting setup for non-shared tags
brd: remove unused brd_mutex
blk-mq: only run the hardware queue if IO is pending
block: avoid null pointer dereference on null disk
fs: guard_bio_eod() needs to consider partitions
xtensa/simdisk: fix compile error
nvme: expose subsys attribute to sysfs
nvme: create 'slaves' and 'holders' entries for hidden controllers
block: create 'slaves' and 'holders' entries for hidden gendisks
nvme: also expose the namespace identification sysfs files for mpath nodes
nvme: implement multipath access to nvme subsystems
nvme: track shared namespaces
nvme: introduce a nvme_ns_ids structure
nvme: track subsystems
block, nvme: Introduce blk_mq_req_flags_t
block, scsi: Make SCSI quiesce and resume work reliably
block: Add the QUEUE_FLAG_PREEMPT_ONLY request queue flag
...
11 Nov, 2017
1 commit
-
kthread() could bail out early before we initialize blkcg_css (if the
kthread is killed very early. Please see xchg() statement in kthread()),
which confuses free_kthread_struct. Instead of moving the blkcg_css
initialization early, we simply zero the whole 'self' data structure,
which doesn't sound much overhead.Reported-by: syzbot
Fixes: 05e3db95ebfc ("kthread: add a mechanism to store cgroup info")
Cc: Andrew Morton
Cc: Ingo Molnar
Cc: Dmitry Vyukov
Acked-by: Tejun Heo
Signed-off-by: Shaohua Li
Signed-off-by: Jens Axboe
05 Oct, 2017
1 commit
-
In preparation for unconditionally passing the struct timer_list pointer
to all timer callbacks, switch kthread to use from_timer() and pass the
timer pointer explicitly.Signed-off-by: Kees Cook
Signed-off-by: Thomas Gleixner
Cc: linux-mips@linux-mips.org
Cc: Len Brown
Cc: Benjamin Herrenschmidt
Cc: Lai Jiangshan
Cc: Sebastian Reichel
Cc: Kalle Valo
Cc: Paul Mackerras
Cc: Pavel Machek
Cc: linux1394-devel@lists.sourceforge.net
Cc: Chris Metcalf
Cc: linux-s390@vger.kernel.org
Cc: linux-wireless@vger.kernel.org
Cc: "James E.J. Bottomley"
Cc: Wim Van Sebroeck
Cc: Michael Ellerman
Cc: Ursula Braun
Cc: Geert Uytterhoeven
Cc: Viresh Kumar
Cc: Harish Patil
Cc: Stephen Boyd
Cc: Guenter Roeck
Cc: Manish Chopra
Cc: Petr Mladek
Cc: Arnd Bergmann
Cc: linux-pm@vger.kernel.org
Cc: Heiko Carstens
Cc: Martin Schwidefsky
Cc: Julian Wiedmann
Cc: John Stultz
Cc: Mark Gross
Cc: linux-watchdog@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: "Martin K. Petersen"
Cc: Greg Kroah-Hartman
Cc: "Rafael J. Wysocki"
Cc: Oleg Nesterov
Cc: Ralf Baechle
Cc: Stefan Richter
Cc: Michael Reed
Cc: netdev@vger.kernel.org
Cc: Tejun Heo
Cc: Andrew Morton
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Sudip Mukherjee
Link: https://lkml.kernel.org/r/1507159627-127660-13-git-send-email-keescook@chromium.org
27 Sep, 2017
1 commit
-
The code is only for blkcg not for all cgroups
Fixes: d4478e92d618 ("block/loop: make loop cgroup aware")
Reported-by: kbuild test robot
Signed-off-by: Shaohua Li
Signed-off-by: Jens Axboe
26 Sep, 2017
1 commit
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kthread usually runs jobs on behalf of other threads. The jobs should be
charged to cgroup of original threads. But the jobs run in a kthread,
where we lose the cgroup context of original threads. The patch adds a
machanism to record cgroup info of original threads in kthread context.
Later we can retrieve the cgroup info and attach the cgroup info to jobs.Since this mechanism is only required by kthread, we store the cgroup
info in kthread data instead of generic task_struct.Acked-by: Tejun Heo
Signed-off-by: Shaohua Li
Signed-off-by: Jens Axboe
01 Sep, 2017
1 commit
-
If the worker thread continues getting work, it will hog the cpu and rcu
stall complains. Make it a good citizen. This is triggered in a loop
block device test.Link: http://lkml.kernel.org/r/5de0a179b3184e1a2183fc503448b0269f24d75b.1503697127.git.shli@fb.com
Signed-off-by: Shaohua Li
Cc: Petr Mladek
Cc: Thomas Gleixner
Cc: Tejun Heo
Cc: Oleg Nesterov
Cc: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
17 Mar, 2017
1 commit
-
Creation of a kthread goes through a couple interlocked stages between
the kthread itself and its creator. Once the new kthread starts
running, it initializes itself and wakes up the creator. The creator
then can further configure the kthread and then let it start doing its
job by waking it up.In this configuration-by-creator stage, the creator is the only one
that can wake it up but the kthread is visible to userland. When
altering the kthread's attributes from userland is allowed, this is
fine; however, for cases where CPU affinity is critical,
kthread_bind() is used to first disable affinity changes from userland
and then set the affinity. This also prevents the kthread from being
migrated into non-root cgroups as that can affect the CPU affinity and
many other things.Unfortunately, the cgroup side of protection is racy. While the
PF_NO_SETAFFINITY flag prevents further migrations, userland can win
the race before the creator sets the flag with kthread_bind() and put
the kthread in a non-root cgroup, which can lead to all sorts of
problems including incorrect CPU affinity and starvation.This bug got triggered by userland which periodically tries to migrate
all processes in the root cpuset cgroup to a non-root one. Per-cpu
workqueue workers got caught while being created and ended up with
incorrected CPU affinity breaking concurrency management and sometimes
stalling workqueue execution.This patch adds task->no_cgroup_migration which disallows the task to
be migrated by userland. kthreadd starts with the flag set making
every child kthread start in the root cgroup with migration
disallowed. The flag is cleared after the kthread finishes
initialization by which time PF_NO_SETAFFINITY is set if the kthread
should stay in the root cgroup.It'd be better to wait for the initialization instead of failing but I
couldn't think of a way of implementing that without adding either a
new PF flag, or sleeping and retrying from waiting side. Even if
userland depends on changing cgroup membership of a kthread, it either
has to be synchronized with kthread_create() or periodically repeat,
so it's unlikely that this would break anything.v2: Switch to a simpler implementation using a new task_struct bit
field suggested by Oleg.Signed-off-by: Tejun Heo
Suggested-by: Oleg Nesterov
Cc: Linus Torvalds
Cc: Andrew Morton
Cc: Peter Zijlstra (Intel)
Cc: Thomas Gleixner
Reported-and-debugged-by: Chris Mason
Cc: stable@vger.kernel.org # v4.3+ (we can't close the race on < v4.3)
Signed-off-by: Tejun Heo
02 Mar, 2017
2 commits
-
We are going to split out of , which
will have to be picked up from other headers and a couple of .c files.Create a trivial placeholder file that just
maps to to make this patch obviously correct and
bisectable.Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar -
We are going to move scheduler ABI details to ,
which will be used from a number of .c files.Create empty placeholder header that maps to .
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar
10 Feb, 2017
1 commit
-
Currently CONFIG_TIMER_STATS exposes process information across namespaces:
kernel/time/timer_list.c print_timer():
SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);
/proc/timer_list:
#11: , hrtimer_wakeup, S:01, do_nanosleep, cron/2570
Given that the tracer can give the same information, this patch entirely
removes CONFIG_TIMER_STATS.Suggested-by: Thomas Gleixner
Signed-off-by: Kees Cook
Acked-by: John Stultz
Cc: Nicolas Pitre
Cc: linux-doc@vger.kernel.org
Cc: Lai Jiangshan
Cc: Shuah Khan
Cc: Xing Gao
Cc: Jonathan Corbet
Cc: Jessica Frazelle
Cc: kernel-hardening@lists.openwall.com
Cc: Nicolas Iooss
Cc: "Paul E. McKenney"
Cc: Petr Mladek
Cc: Richard Cochran
Cc: Tejun Heo
Cc: Michal Marek
Cc: Josh Poimboeuf
Cc: Dmitry Vyukov
Cc: Oleg Nesterov
Cc: "Eric W. Biederman"
Cc: Olof Johansson
Cc: Andrew Morton
Cc: linux-api@vger.kernel.org
Cc: Arjan van de Ven
Link: http://lkml.kernel.org/r/20170208192659.GA32582@beast
Signed-off-by: Thomas Gleixner
13 Dec, 2016
1 commit
-
When commit fbae2d44aa1d ("kthread: add kthread_create_worker*()")
introduced some kthread_create_...() functions which were taking
printf-like parametter, it introduced __printf attributes to some
functions (e.g. kthread_create_worker()). Nevertheless some new
functions were forgotten (they have been detected thanks to
-Wmissing-format-attribute warning flag).Add the missing __printf attributes to the newly-introduced functions in
order to detect formatting issues at build-time with -Wformat flag.Link: http://lkml.kernel.org/r/20161126193543.22672-1-nicolas.iooss_linux@m4x.org
Signed-off-by: Nicolas Iooss
Reviewed-by: Petr Mladek
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
08 Dec, 2016
5 commits
-
kthread_create_on_cpu() sets KTHREAD_IS_PER_CPU and kthread->cpu, this
only makes sense if this kthread can be parked/unparked by cpuhp code.
kthread workers never call kthread_parkme() so this has no effect.Change __kthread_create_worker() to simply call kthread_bind(task, cpu).
The very fact that kthread_create_on_cpu() doesn't accept a generic fmt
shows that it should not be used outside of smpboot.c.Now, the only reason we can not unexport this helper and move it into
smpboot.c is that it sets kthread->cpu and struct kthread is not exported.
And the only reason we can not kill kthread->cpu is that kthread_unpark()
is used by drivers/gpu/drm/amd/scheduler/gpu_scheduler.c and thus we can
not turn _unpark into kthread_unpark(struct smp_hotplug_thread *, cpu).Signed-off-by: Oleg Nesterov
Tested-by: Petr Mladek
Acked-by: Peter Zijlstra (Intel)
Reviewed-by: Petr Mladek
Cc: Chunming Zhou
Cc: Roman Pen
Cc: Andy Lutomirski
Cc: Tejun Heo
Cc: Andy Lutomirski
Cc: Alex Deucher
Cc: Andrew Morton
Link: http://lkml.kernel.org/r/20161129175110.GA5342@redhat.com
Signed-off-by: Thomas Gleixner -
Now that to_kthread() is always validm change kthread_park() and
kthread_unpark() to use it and kill to_live_kthread().The conversion of kthread_unpark() is trivial. If KTHREAD_IS_PARKED is set
then the task has called complete(&self->parked) and there the function
cannot race against a concurrent kthread_stop() and exit.kthread_park() is more tricky, because its semantics are not well
defined. It returns -ENOSYS if the thread exited but this can never happen
and as Roman pointed out kthread_park() can obviously block forever if it
would race with the exiting kthread.The usage of kthread_park() in cpuhp code (cpu.c, smpboot.c, stop_machine.c)
is fine. It can never see an exiting/exited kthread, smpboot_destroy_threads()
clears *ht->store, smpboot_park_thread() checks it is not NULL under the same
smpboot_threads_lock. cpuhp_threads and cpu_stop_threads never exit, so other
callers are fine too.But it has two more users:
- watchdog_park_threads():
The code is actually correct, get_online_cpus() ensures that
kthread_park() can't race with itself (note that kthread_park() can't
handle this race correctly), but it should not use kthread_park()
directly.- drivers/gpu/drm/amd/scheduler/gpu_scheduler.c should not use
kthread_park() either.kthread_park() must not be called after amd_sched_fini() which does
kthread_stop(), otherwise even to_live_kthread() is not safe because
task_struct can be already freed and sched->thread can point to nowhere.The usage of kthread_park/unpark should either be restricted to core code
which is properly protected against the exit race or made more robust so it
is safe to use it in drivers.To catch eventual exit issues, add a WARN_ON(PF_EXITING) for now.
Signed-off-by: Oleg Nesterov
Acked-by: Peter Zijlstra (Intel)
Reviewed-by: Thomas Gleixner
Cc: Chunming Zhou
Cc: Roman Pen
Cc: Petr Mladek
Cc: Andy Lutomirski
Cc: Tejun Heo
Cc: Andy Lutomirski
Cc: Alex Deucher
Cc: Andrew Morton
Link: http://lkml.kernel.org/r/20161129175107.GA5339@redhat.com
Signed-off-by: Thomas Gleixner -
kthread_stop() had to use to_live_kthread() simply because it was not
possible to access kthread->exited after the exiting task clears
task_struct->vfork_done. Now that to_kthread() is always valid,
wake_up_process() + wait_for_completion() can be done
ununconditionally. It's not an issue anymore if the task has already issued
complete_vfork_done() or died.The exiting task can get the spurious wakeup after mm_release() but this is
possible without this change too and is fine; do_task_dead() ensures that
this can't make any harm.As a further enhancement this could be converted to task_work_add() later,
so ->vfork_done can be avoided completely.Signed-off-by: Oleg Nesterov
Acked-by: Peter Zijlstra (Intel)
Reviewed-by: Thomas Gleixner
Cc: Chunming Zhou
Cc: Roman Pen
Cc: Petr Mladek
Cc: Andy Lutomirski
Cc: Tejun Heo
Cc: Andy Lutomirski
Cc: Alex Deucher
Cc: Andrew Morton
Link: http://lkml.kernel.org/r/20161129175103.GA5336@redhat.com
Signed-off-by: Thomas Gleixner -
…ive_kthread() function"
This reverts commit 23196f2e5f5d810578a772785807dcdc2b9fdce9.
Now that struct kthread is kmalloc'ed and not longer on the task stack
there is no need anymore to pin the stack.Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chunming Zhou <David1.Zhou@amd.com>
Cc: Roman Pen <roman.penyaev@profitbricks.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20161129175100.GA5333@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> -
commit 23196f2e5f5d "kthread: Pin the stack via try_get_task_stack() /
put_task_stack() in to_live_kthread() function" is a workaround for the
fragile design of struct kthread being allocated on the task stack.struct kthread in its current form should be removed, but this needs
cleanups outside of kthread.c.As a first step move struct kthread away from the task stack by making it
kmalloc'ed. This allows to access kthread.exited without the magic of
trying to pin task stack and the try logic in to_live_kthread().Signed-off-by: Oleg Nesterov
Acked-by: Peter Zijlstra (Intel)
Reviewed-by: Thomas Gleixner
Cc: Chunming Zhou
Cc: Roman Pen
Cc: Petr Mladek
Cc: Andy Lutomirski
Cc: Tejun Heo
Cc: Andy Lutomirski
Cc: Alex Deucher
Cc: Andrew Morton
Link: http://lkml.kernel.org/r/20161129175057.GA5330@redhat.com
Signed-off-by: Thomas Gleixner
12 Oct, 2016
11 commits
-
This patch allows to make kthread worker freezable via a new @flags
parameter. It will allow to avoid an init work in some kthreads.It currently does not affect the function of kthread_worker_fn()
but it might help to do some optimization or fixes eventually.I currently do not know about any other use for the @flags
parameter but I believe that we will want more flags
in the future.Finally, I hope that it will not cause confusion with @flags member
in struct kthread. Well, I guess that we will want to rework the
basic kthreads implementation once all kthreads are converted into
kthread workers or workqueues. It is possible that we will merge
the two structures.Link: http://lkml.kernel.org/r/1470754545-17632-12-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Acked-by: Tejun Heo
Cc: Oleg Nesterov
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
There are situations when we need to modify the delay of a delayed kthread
work. For example, when the work depends on an event and the initial delay
means a timeout. Then we want to queue the work immediately when the event
happens.This patch implements kthread_mod_delayed_work() as inspired workqueues.
It cancels the timer, removes the work from any worker list and queues it
again with the given timeout.A very special case is when the work is being canceled at the same time.
It might happen because of the regular kthread_cancel_delayed_work_sync()
or by another kthread_mod_delayed_work(). In this case, we do nothing and
let the other operation win. This should not normally happen as the caller
is supposed to synchronize these operations a reasonable way.Link: http://lkml.kernel.org/r/1470754545-17632-11-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Acked-by: Tejun Heo
Cc: Oleg Nesterov
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We are going to use kthread workers more widely and sometimes we will need
to make sure that the work is neither pending nor running.This patch implements cancel_*_sync() operations as inspired by
workqueues. Well, we are synchronized against the other operations via
the worker lock, we use del_timer_sync() and a counter to count parallel
cancel operations. Therefore the implementation might be easier.First, we check if a worker is assigned. If not, the work has newer been
queued after it was initialized.Second, we take the worker lock. It must be the right one. The work must
not be assigned to another worker unless it is initialized in between.Third, we try to cancel the timer when it exists. The timer is deleted
synchronously to make sure that the timer call back is not running. We
need to temporary release the worker->lock to avoid a possible deadlock
with the callback. In the meantime, we set work->canceling counter to
avoid any queuing.Fourth, we try to remove the work from a worker list. It might be
the list of either normal or delayed works.Fifth, if the work is running, we call kthread_flush_work(). It might
take an arbitrary time. We need to release the worker-lock again. In the
meantime, we again block any queuing by the canceling counter.As already mentioned, the check for a pending kthread work is done under a
lock. In compare with workqueues, we do not need to fight for a single
PENDING bit to block other operations. Therefore we do not suffer from
the thundering storm problem and all parallel canceling jobs might use
kthread_flush_work(). Any queuing is blocked until the counter gets zero.Link: http://lkml.kernel.org/r/1470754545-17632-10-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Acked-by: Tejun Heo
Cc: Oleg Nesterov
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We are going to use kthread_worker more widely and delayed works
will be pretty useful.The implementation is inspired by workqueues. It uses a timer to queue
the work after the requested delay. If the delay is zero, the work is
queued immediately.In compare with workqueues, each work is associated with a single worker
(kthread). Therefore the implementation could be much easier. In
particular, we use the worker->lock to synchronize all the operations with
the work. We do not need any atomic operation with a flags variable.In fact, we do not need any state variable at all. Instead, we add a list
of delayed works into the worker. Then the pending work is listed either
in the list of queued or delayed works. And the existing check of pending
works is the same even for the delayed ones.A work must not be assigned to another worker unless reinitialized.
Therefore the timer handler might expect that dwork->work->worker is valid
and it could simply take the lock. We just add some sanity checks to help
with debugging a potential misuse.Link: http://lkml.kernel.org/r/1470754545-17632-9-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Acked-by: Tejun Heo
Cc: Oleg Nesterov
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Nothing currently prevents a work from queuing for a kthread worker when
it is already running on another one. This means that the work might run
in parallel on more than one worker. Also some operations are not
reliable, e.g. flush.This problem will be even more visible after we add kthread_cancel_work()
function. It will only have "work" as the parameter and will use
worker->lock to synchronize with others.Well, normally this is not a problem because the API users are sane.
But bugs might happen and users also might be crazy.This patch adds a warning when we try to insert the work for another
worker. It does not fully prevent the misuse because it would make the
code much more complicated without a big benefit.It adds the same warning also into kthread_flush_work() instead of the
repeated attempts to get the right lock.A side effect is that one needs to explicitly reinitialize the work if it
must be queued into another worker. This is needed, for example, when the
worker is stopped and started again. It is a bit inconvenient. But it
looks like a good compromise between the stability and complexity.I have double checked all existing users of the kthread worker API and
they all seems to initialize the work after the worker gets started.Just for completeness, the patch adds a check that the work is not already
in a queue.The patch also puts all the checks into a separate function. It will be
reused when implementing delayed works.Link: http://lkml.kernel.org/r/1470754545-17632-8-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Cc: Oleg Nesterov
Cc: Tejun Heo
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The current kthread worker users call flush() and stop() explicitly.
This function does the same plus it frees the kthread_worker struct
in one call.It is supposed to be used together with kthread_create_worker*() that
allocates struct kthread_worker.Link: http://lkml.kernel.org/r/1470754545-17632-7-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Cc: Oleg Nesterov
Cc: Tejun Heo
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Kthread workers are currently created using the classic kthread API,
namely kthread_run(). kthread_worker_fn() is passed as the @threadfn
parameter.This patch defines kthread_create_worker() and
kthread_create_worker_on_cpu() functions that hide implementation details.They enforce using kthread_worker_fn() for the main thread. But I doubt
that there are any plans to create any alternative. In fact, I think that
we do not want any alternative main thread because it would be hard to
support consistency with the rest of the kthread worker API.The naming and function of kthread_create_worker() is inspired by the
workqueues API like the rest of the kthread worker API.The kthread_create_worker_on_cpu() variant is motivated by the original
kthread_create_on_cpu(). Note that we need to bind per-CPU kthread
workers already when they are created. It makes the life easier.
kthread_bind() could not be used later for an already running worker.This patch does _not_ convert existing kthread workers. The kthread
worker API need more improvements first, e.g. a function to destroy the
worker.IMPORTANT:
kthread_create_worker_on_cpu() allows to use any format of the worker
name, in compare with kthread_create_on_cpu(). The good thing is that it
is more generic. The bad thing is that most users will need to pass the
cpu number in two parameters, e.g. kthread_create_worker_on_cpu(cpu,
"helper/%d", cpu).To be honest, the main motivation was to avoid the need for an empty
va_list. The only legal way was to create a helper function that would be
called with an empty list. Other attempts caused compilation warnings or
even errors on different architectures.There were also other alternatives, for example, using #define or
splitting __kthread_create_worker(). The used solution looked like the
least ugly.Link: http://lkml.kernel.org/r/1470754545-17632-6-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Acked-by: Tejun Heo
Cc: Oleg Nesterov
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
kthread_create_on_node() implements a bunch of logic to create the
kthread. It is already called by kthread_create_on_cpu().We are going to extend the kthread worker API and will need to call
kthread_create_on_node() with va_list args there.This patch does only a refactoring and does not modify the existing
behavior.Link: http://lkml.kernel.org/r/1470754545-17632-5-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Acked-by: Tejun Heo
Cc: Oleg Nesterov
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
kthread_create_on_cpu() was added by the commit 2a1d446019f9a5983e
("kthread: Implement park/unpark facility"). It is currently used only
when enabling new CPU. For this purpose, the newly created kthread has to
be parked.The CPU binding is a bit tricky. The kthread is parked when the CPU has
not been allowed yet. And the CPU is bound when the kthread is unparked.The function would be useful for more per-CPU kthreads, e.g.
bnx2fc_thread, fcoethread. For this purpose, the newly created kthread
should stay in the uninterruptible state.This patch moves the parking into smpboot. It binds the thread already
when created. Then the function might be used universally. Also the
behavior is consistent with kthread_create() and kthread_create_on_node().Link: http://lkml.kernel.org/r/1470754545-17632-4-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Reviewed-by: Thomas Gleixner
Cc: Oleg Nesterov
Cc: Tejun Heo
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
A good practice is to prefix the names of functions by the name
of the subsystem.The kthread worker API is a mix of classic kthreads and workqueues. Each
worker has a dedicated kthread. It runs a generic function that process
queued works. It is implemented as part of the kthread subsystem.This patch renames the existing kthread worker API to use
the corresponding name from the workqueues API prefixed by
kthread_:__init_kthread_worker() -> __kthread_init_worker()
init_kthread_worker() -> kthread_init_worker()
init_kthread_work() -> kthread_init_work()
insert_kthread_work() -> kthread_insert_work()
queue_kthread_work() -> kthread_queue_work()
flush_kthread_work() -> kthread_flush_work()
flush_kthread_worker() -> kthread_flush_worker()Note that the names of DEFINE_KTHREAD_WORK*() macros stay
as they are. It is common that the "DEFINE_" prefix has
precedence over the subsystem names.Note that INIT() macros and init() functions use different
naming scheme. There is no good solution. There are several
reasons for this solution:+ "init" in the function names stands for the verb "initialize"
aka "initialize worker". While "INIT" in the macro names
stands for the noun "INITIALIZER" aka "worker initializer".+ INIT() macros are used only in DEFINE() macros
+ init() functions are used close to the other kthread()
functions. It looks much better if all the functions
use the same scheme.+ There will be also kthread_destroy_worker() that will
be used close to kthread_cancel_work(). It is related
to the init() function. Again it looks better if all
functions use the same naming scheme.+ there are several precedents for such init() function
names, e.g. amd_iommu_init_device(), free_area_init_node(),
jump_label_init_type(), regmap_init_mmio_clk(),+ It is not an argument but it was inconsistent even before.
[arnd@arndb.de: fix linux-next merge conflict]
Link: http://lkml.kernel.org/r/20160908135724.1311726-1-arnd@arndb.de
Link: http://lkml.kernel.org/r/1470754545-17632-3-git-send-email-pmladek@suse.com
Suggested-by: Andrew Morton
Signed-off-by: Petr Mladek
Cc: Oleg Nesterov
Cc: Tejun Heo
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Arnd Bergmann
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Patch series "kthread: Kthread worker API improvements"
The intention of this patchset is to make it easier to manipulate and
maintain kthreads. Especially, I want to replace all the custom main
cycles with a generic one. Also I want to make the kthreads sleep in a
consistent state in a common place when there is no work.This patch (of 11):
A good practice is to prefix the names of functions by the name of the
subsystem.This patch fixes the name of probe_kthread_data(). The other wrong
functions names are part of the kthread worker API and will be fixed
separately.Link: http://lkml.kernel.org/r/1470754545-17632-2-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek
Suggested-by: Andrew Morton
Acked-by: Tejun Heo
Cc: Oleg Nesterov
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: "Paul E. McKenney"
Cc: Josh Triplett
Cc: Thomas Gleixner
Cc: Jiri Kosina
Cc: Borislav Petkov
Cc: Michal Hocko
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
16 Sep, 2016
1 commit
-
get_task_struct(tsk) no longer pins tsk->stack so all users of
to_live_kthread() should do try_get_task_stack/put_task_stack to protect
"struct kthread" which lives on kthread's stack.TODO: Kill to_live_kthread(), perhaps we can even kill "struct kthread" too,
and rework kthread_stop(), it can use task_work_add() to sync with the exiting
kernel thread.Message-Id:
Signed-off-by: Oleg Nesterov
Signed-off-by: Andy Lutomirski
Cc: Borislav Petkov
Cc: Brian Gerst
Cc: Denys Vlasenko
Cc: H. Peter Anvin
Cc: Jann Horn
Cc: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/cb9b16bbc19d4aea4507ab0552e4644c1211d130.1474003868.git.luto@kernel.org
Signed-off-by: Ingo Molnar
05 Sep, 2015
1 commit
-
- Make it clear that the `node' arg refers to memory allocations only:
kthread_create_on_node() does not pin the new thread to that node's
CPUs.- Encourage the use of NUMA_NO_NODE.
[nzimmer@sgi.com: use NUMA_NO_NODE in kthread_create() also]
Cc: Nathan Zimmer
Cc: Tejun Heo
Cc: Eric Dumazet
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
01 Sep, 2015
1 commit
-
Pull scheduler updates from Ingo Molnar:
"The biggest change in this cycle is the rewrite of the main SMP load
balancing metric: the CPU load/utilization. The main goal was to make
the metric more precise and more representative - see the changelog of
this commit for the gory details:9d89c257dfb9 ("sched/fair: Rewrite runnable load and utilization average tracking")
It is done in a way that significantly reduces complexity of the code:
5 files changed, 249 insertions(+), 494 deletions(-)
and the performance testing results are encouraging. Nevertheless we
need to keep an eye on potential regressions, since this potentially
affects every SMP workload in existence.This work comes from Yuyang Du.
Other changes:
- SCHED_DL updates. (Andrea Parri)
- Simplify architecture callbacks by removing finish_arch_switch().
(Peter Zijlstra et al)- cputime accounting: guarantee stime + utime == rtime. (Peter
Zijlstra)- optimize idle CPU wakeups some more - inspired by Facebook server
loads. (Mike Galbraith)- stop_machine fixes and updates. (Oleg Nesterov)
- Introduce the 'trace_sched_waking' tracepoint. (Peter Zijlstra)
- sched/numa tweaks. (Srikar Dronamraju)
- misc fixes and small cleanups"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
sched/deadline: Fix comment in enqueue_task_dl()
sched/deadline: Fix comment in push_dl_tasks()
sched: Change the sched_class::set_cpus_allowed() calling context
sched: Make sched_class::set_cpus_allowed() unconditional
sched: Fix a race between __kthread_bind() and sched_setaffinity()
sched: Ensure a task has a non-normalized vruntime when returning back to CFS
sched/numa: Fix NUMA_DIRECT topology identification
tile: Reorganize _switch_to()
sched, sparc32: Update scheduler comments in copy_thread()
sched: Remove finish_arch_switch()
sched, tile: Remove finish_arch_switch
sched, sh: Fold finish_arch_switch() into switch_to()
sched, score: Remove finish_arch_switch()
sched, avr32: Remove finish_arch_switch()
sched, MIPS: Get rid of finish_arch_switch()
sched, arm: Remove finish_arch_switch()
sched/fair: Clean up load average references
sched/fair: Provide runnable_load_avg back to cfs_rq
sched/fair: Remove task and group entity load when they are dead
sched/fair: Init cfs_rq's sched_entity load average
...
12 Aug, 2015
1 commit
-
Because sched_setscheduler() checks p->flags & PF_NO_SETAFFINITY
without locks, a caller might observe an old value and race with the
set_cpus_allowed_ptr() call from __kthread_bind() and effectively undo
it:__kthread_bind()
do_set_cpus_allowed()
sched_setaffinity()
if (p->flags & PF_NO_SETAFFINITIY)
set_cpus_allowed_ptr()
p->flags |= PF_NO_SETAFFINITYFix the bug by putting everything under the regular scheduler locks.
This also closes a hole in the serialization of task_struct::{nr_,}cpus_allowed.
Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Tejun Heo
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Oleg Nesterov
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: dedekind1@gmail.com
Cc: juri.lelli@arm.com
Cc: mgorman@suse.de
Cc: riel@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/20150515154833.545640346@infradead.org
Signed-off-by: Ingo Molnar
07 Aug, 2015
1 commit
-
The s-Par visornic driver, currently in staging, processes a queue being
serviced by the an s-Par service partition. We can get a message that
something has happened with the Service Partition, when that happens, we
must not access the channel until we get a message that the service
partition is back again.The visornic driver has a thread for processing the channel, when we get
the message, we need to be able to park the thread and then resume it
when the problem clears.We can do this with kthread_park and unpark but they are not exported
from the kernel, this patch exports the needed functions.Signed-off-by: David Kershner
Acked-by: Ingo Molnar
Acked-by: Neil Horman
Acked-by: Thomas Gleixner
Cc: Richard Weinberger
Cc: Tejun Heo
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
