24 Nov, 2011
2 commits
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There's no in-kernel user of set_freezable_with_signal() left. Mixing
TIF_SIGPENDING with kernel threads can lead to nasty corner cases as
kernel threads never travel signal delivery path on their own.e.g. the current implementation is buggy in the cancelation path of
__thaw_task(). It calls recalc_sigpending_and_wake() in an attempt to
clear TIF_SIGPENDING but the function never clears it regardless of
sigpending state. This means that signallable freezable kthreads may
continue executing with !freezing() && stuck TIF_SIGPENDING, which can
be troublesome.This patch removes set_freezable_with_signal() along with
PF_FREEZER_NOSIG and recalc_sigpending*() calls in freezer. User
tasks get TIF_SIGPENDING, kernel tasks get woken up and the spurious
sigpending is dealt with in the usual signal delivery path.Signed-off-by: Tejun Heo
Acked-by: Oleg Nesterov -
Commit 981ed70d8e (dmatest: make dmatest threads freezable) made
dmatest kthread use set_freezable_with_signal(); however, the
interface is scheduled to be removed in the next merge window.The problem is that unlike userland tasks there's no default place
which handles signal pending state and it isn't clear who owns and/or
is responsible for clearing TIF_SIGPENDING. For example, in the
current code, try_to_freeze() clears TIF_SIGPENDING but it isn't sure
whether it actually owns the TIF_SIGPENDING nor is it race-free -
ie. the task may continue to run with TIF_SIGPENDING set after the
freezable section.Unfortunately, we don't have wait_for_completion_freezable_timeout().
This patch open codes it and uses wait_event_freezable_timeout()
instead and removes timeout reloading - wait_event_freezable_timeout()
won't return across freezing events (currently racy but fix scheduled)
and timer doesn't decrement while the task is in freezer. Although
this does lose timer-reset-over-freezing, given that timeout is
supposed to be long enough and failure to finish inside is considered
irrecoverable, I don't think this is worth the complexity.While at it, move completion to outer scope and explain that we're
ignoring dangling pointer problem after timeout. This should give
slightly better chance at avoiding oops after timeout.Signed-off-by: Tejun Heo
Acked-by: Dan Williams
Cc: Guennadi Liakhovetski
Cc: Nicolas Ferre
22 Nov, 2011
21 commits
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The current implementation of set_freezable_with_signal() is buggy and
tricky to get right. usb-storage is the only user and its use can be
avoided trivially.All usb-storage wants is to be able to sleep with timeout and get
woken up if freezing() becomes true. This can be trivially
implemented by doing interruptible wait w/ freezing() included in the
wait condition. There's no reason to use set_freezable_with_signal().Perform interruptible wait on freezing() instead of using
set_freezable_with_signal(), which is scheduled for removal.Signed-off-by: Tejun Heo
Cc: Oleg Nesterov
Cc: "Rafael J. Wysocki"
Cc: Seth Forshee
Cc: Alan Stern
Cc: Greg Kroah-Hartman -
After "freezer: make freezing() test freeze conditions in effect
instead of TIF_FREEZE", freezing() returns authoritative answer on
whether the current task should freeze or not and freeze_task()
doesn't need or use @sig_only. Remove it.While at it, rewrite function comment for freeze_task() and rename
@sig_only to @user_only in try_to_freeze_tasks().This patch doesn't cause any functional change.
Signed-off-by: Tejun Heo
Acked-by: Oleg Nesterov -
cgroup_freezer calls freeze_task() without holding tasklist_lock and,
if the task is exiting, its ->sighand may be gone by the time
fake_signal_wake_up() is called. Use lock_task_sighand() instead of
accessing ->sighand directly.Signed-off-by: Tejun Heo
Reported-by: Oleg Nesterov
Acked-by: Oleg Nesterov
Cc: "Rafael J. Wysocki"
Cc: Paul Menage -
If another freeze happens before all tasks leave FROZEN state after
being thawed, the freezer can see the existing FROZEN and consider the
tasks to be frozen but they can clear FROZEN without checking the new
freezing().Oleg suggested restructuring __refrigerator() such that there's single
condition check section inside freezer_lock and sigpending is cleared
afterwards, which fixes the problem and simplifies the code.
Restructure accordingly.-v2: Frozen loop exited without releasing freezer_lock. Fixed.
Signed-off-by: Tejun Heo
Reported-by: Oleg Nesterov
Acked-by: Oleg Nesterov
Cc: "Rafael J. Wysocki" -
A kthread doing set_freezable*() may race with on-going PM freeze and
the freezer might think all tasks are frozen while the new freezable
kthread is merrily proceeding to execute code paths which aren't
supposed to be executing during PM freeze.Reimplement set_freezable[_with_signal]() using __set_freezable() such
that freezable PF flags are modified under freezer_lock and
try_to_freeze() is called afterwards. This eliminates race condition
against freezing.Note: Separated out from larger patch to resolve fix order dependency
Oleg pointed out.Signed-off-by: Tejun Heo
Cc: Oleg Nesterov -
should_send_signal() is only used in freezer.c. Exporting them only
increases chance of abuse. Open code the two users and remove it.Update frozen() to return bool.
Signed-off-by: Tejun Heo
-
Signed-off-by: Tejun Heo
Cc: Arnd Bergmann
Cc: linux-arch@vger.kernel.org -
Using TIF_FREEZE for freezing worked when there was only single
freezing condition (the PM one); however, now there is also the
cgroup_freezer and single bit flag is getting clumsy.
thaw_processes() is already testing whether cgroup freezing in in
effect to avoid thawing tasks which were frozen by both PM and cgroup
freezers.This is racy (nothing prevents race against cgroup freezing) and
fragile. A much simpler way is to test actual freeze conditions from
freezing() - ie. directly test whether PM or cgroup freezing is in
effect.This patch adds variables to indicate whether and what type of
freezing conditions are in effect and reimplements freezing() such
that it directly tests whether any of the two freezing conditions is
active and the task should freeze. On fast path, freezing() is still
very cheap - it only tests system_freezing_cnt.This makes the clumsy dancing aroung TIF_FREEZE unnecessary and
freeze/thaw operations more usual - updating state variables for the
new state and nudging target tasks so that they notice the new state
and comply. As long as the nudging happens after state update, it's
race-free.* This allows use of freezing() in freeze_task(). Replace the open
coded tests with freezing().* p != current test is added to warning printing conditions in
try_to_freeze_tasks() failure path. This is necessary as freezing()
is now true for the task which initiated freezing too.-v2: Oleg pointed out that re-freezing FROZEN cgroup could increment
system_freezing_cnt. Fixed.Signed-off-by: Tejun Heo
Acked-by: Paul Menage (for the cgroup portions) -
TIF_FREEZE will be removed soon and freezing() will directly test
whether any freezing condition is in effect. Make the following
changes in preparation.* Rename cgroup_freezing_or_frozen() to cgroup_freezing() and make it
return bool.* Make cgroup_freezing() access task_freezer() under rcu read lock
instead of task_lock(). This makes the state dereferencing racy
against task moving to another cgroup; however, it was already racy
without this change as ->state dereference wasn't synchronized.
This will be later dealt with using attach hooks.* freezer->state is now set before trying to push tasks into the
target state.-v2: Oleg pointed out that freeze_change_state() was setting
freeze->state incorrectly to CGROUP_FROZEN instead of
CGROUP_FREEZING. Fixed.-v3: Matt pointed out that setting CGROUP_FROZEN used to always invoke
try_to_freeze_cgroup() regardless of the current state. Patch
updated such that the actual freeze/thaw operations are always
performed on invocation. This shouldn't make any difference
unless something is broken.Signed-off-by: Tejun Heo
Acked-by: Paul Menage
Cc: Li Zefan
Cc: Oleg Nesterov -
freeze_processes() failure path is rather messy. Freezing is canceled
for workqueues and tasks which aren't frozen yet but frozen tasks are
left alone and should be thawed by the caller and of course some
callers (xen and kexec) didn't do it.This patch updates __thaw_task() to handle cancelation correctly and
makes freeze_processes() and freeze_kernel_threads() call
thaw_processes() on failure instead so that the system is fully thawed
on failure. Unnecessary [suspend_]thaw_processes() calls are removed
from kernel/power/hibernate.c, suspend.c and user.c.While at it, restructure error checking if clause in suspend_prepare()
to be less weird.-v2: Srivatsa spotted missing removal of suspend_thaw_processes() in
suspend_prepare() and error in commit message. Updated.Signed-off-by: Tejun Heo
Acked-by: Srivatsa S. Bhat -
With the previous changes, there's no meaningful difference between
PF_FREEZING and PF_FROZEN. Remove PF_FREEZING and use PF_FROZEN
instead in task_contributes_to_load().Signed-off-by: Tejun Heo
-
try_to_freeze_tasks() and thaw_processes() use freezable() and
frozen() as preliminary tests before initiating operations on a task.
These are done without any synchronization and hinder with
synchronization cleanup without any real performance benefits.In try_to_freeze_tasks(), open code self test and move PF_NOFREEZE and
frozen() tests inside freezer_lock in freeze_task().thaw_processes() can simply drop freezable() test as frozen() test in
__thaw_task() is enough.Note: This used to be a part of larger patch to fix set_freezable()
race. Separated out to satisfy ordering among dependent fixes.Signed-off-by: Tejun Heo
Cc: Oleg Nesterov -
Currently freezing (TIF_FREEZE) and frozen (PF_FROZEN) states are
interlocked - freezing is set to request freeze and when the task
actually freezes, it clears freezing and sets frozen.This interlocking makes things more complex than necessary - freezing
doesn't mean there's freezing condition in effect and frozen doesn't
match the task actually entering and leaving frozen state (it's
cleared by the thawing task).This patch makes freezing indicate that freeze condition is in effect.
A task enters and stays frozen if freezing. This makes PF_FROZEN
manipulation done only by the task itself and prevents wakeup from
__thaw_task() leaking outside of refrigerator.The only place which needs to tell freezing && !frozen is
try_to_freeze_task() to whine about tasks which don't enter frozen.
It's updated to test the condition explicitly.With the change, frozen() state my linger after __thaw_task() until
the task wakes up and exits fridge. This can trigger BUG_ON() in
update_if_frozen(). Work it around by testing freezing() && frozen()
instead of frozen().-v2: Oleg pointed out missing re-check of freezing() when trying to
clear FROZEN and possible spurious BUG_ON() trigger in
update_if_frozen(). Both fixed.Signed-off-by: Tejun Heo
Cc: Oleg Nesterov
Cc: Paul Menage -
Freezer synchronization is needlessly complicated - it's by no means a
hot path and the priority is staying unintrusive and safe. This patch
makes it simply use a dedicated lock instead of piggy-backing on
task_lock() and playing with memory barriers.On the failure path of try_to_freeze_tasks(), locking is moved from it
to cancel_freezing(). This makes the frozen() test racy but the race
here is a non-issue as the warning is printed for tasks which failed
to enter frozen for 20 seconds and race on PF_FROZEN at the last
moment doesn't change anything.This simplifies freezer implementation and eases further changes
including some race fixes.Signed-off-by: Tejun Heo
-
There's no point in thawing nosig tasks before others. There's no
ordering requirement between the two groups on thaw, which the staged
thawing can't guarantee anyway. Simplify thaw_processes() by removing
the distinction and collapsing thaw_tasks() into thaw_processes().
This will help further updates to freezer.Signed-off-by: Tejun Heo
-
clear_freeze_flag() in exit_mm() is racy. Freezing can start
afterwards. Remove it. Skipping freezer for exiting task will be
properly implemented later.Also, freezable() was testing exit_state directly to make system
freezer ignore dead tasks. Let the exiting task set PF_NOFREEZE after
entering TASK_DEAD instead.Signed-off-by: Tejun Heo
Cc: Oleg Nesterov -
thaw_process() now has only internal users - system and cgroup
freezers. Remove the unnecessary return value, rename, unexport and
collapse __thaw_process() into it. This will help further updates to
the freezer code.-v3: oom_kill grew a use of thaw_process() while this patch was
pending. Convert it to use __thaw_task() for now. In the longer
term, this should be handled by allowing tasks to die if killed
even if it's frozen.-v2: minor style update as suggested by Matt.
Signed-off-by: Tejun Heo
Cc: Paul Menage
Cc: Matt Helsley -
Writeback and thinkpad_acpi have been using thaw_process() to prevent
deadlock between the freezer and kthread_stop(); unfortunately, this
is inherently racy - nothing prevents freezing from happening between
thaw_process() and kthread_stop().This patch implements kthread_freezable_should_stop() which enters
refrigerator if necessary but is guaranteed to return if
kthread_stop() is invoked. Both thaw_process() users are converted to
use the new function.Note that this deadlock condition exists for many of freezable
kthreads. They need to be converted to use the new should_stop or
freezable workqueue.Tested with synthetic test case.
Signed-off-by: Tejun Heo
Acked-by: Henrique de Moraes Holschuh
Cc: Jens Axboe
Cc: Oleg Nesterov -
There is no reason to export two functions for entering the
refrigerator. Calling refrigerator() instead of try_to_freeze()
doesn't save anything noticeable or removes any race condition.* Rename refrigerator() to __refrigerator() and make it return bool
indicating whether it scheduled out for freezing.* Update try_to_freeze() to return bool and relay the return value of
__refrigerator() if freezing().* Convert all refrigerator() users to try_to_freeze().
* Update documentation accordingly.
* While at it, add might_sleep() to try_to_freeze().
Signed-off-by: Tejun Heo
Cc: Samuel Ortiz
Cc: Chris Mason
Cc: "Theodore Ts'o"
Cc: Steven Whitehouse
Cc: Andrew Morton
Cc: Jan Kara
Cc: KONISHI Ryusuke
Cc: Christoph Hellwig -
Some drivers set PF_NOFREEZE in their kthread functions which is
completely unnecessary and racy - some part of freezer code doesn't
consider cases where PF_NOFREEZE is set asynchronous to freezer
operations.In general, there's no reason to allow setting PF_NOFREEZE explicitly.
Remove them and change the documentation to note that setting
PF_NOFREEZE directly isn't allowed.-v2: Dropped change to twl4030-irq.c as it no longer uses PF_NOFREEZE.
Signed-off-by: Tejun Heo
Acked-by: "Gustavo F. Padovan"
Acked-by: Samuel Ortiz
Cc: Marcel Holtmann
Cc: wwang -
refrigerator() saves current->state before entering frozen state and
restores it before returning using __set_current_state(); however,
this is racy, for example, please consider the following sequence.set_current_state(TASK_INTERRUPTIBLE);
try_to_freeze();
if (kthread_should_stop())
break;
schedule();If kthread_stop() races with ->state restoration, the restoration can
restore ->state to TASK_INTERRUPTIBLE after kthread_stop() sets it to
TASK_RUNNING but kthread_should_stop() may still see zero
->should_stop because there's no memory barrier between restoring
TASK_INTERRUPTIBLE and kthread_should_stop() test.This isn't restricted to kthread_should_stop(). current->state is
often used in memory barrier based synchronization and silently
restoring it w/o mb breaks them.Use set_current_state() instead.
Signed-off-by: Tejun Heo
21 Nov, 2011
4 commits
-
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (86 commits)
ipv4: fix redirect handling
ping: dont increment ICMP_MIB_INERRORS
sky2: fix hang in napi_disable
sky2: enforce minimum ring size
bonding: Don't allow mode change via sysfs with slaves present
f_phonet: fix page offset of first received fragment
stmmac: fix pm functions avoiding sleep on spinlock
stmmac: remove spin_lock in stmmac_ioctl.
stmmac: parameters auto-tuning through HW cap reg
stmmac: fix advertising 1000Base capabilties for non GMII iface
stmmac: use mdelay on timeout of sw reset
sky2: version 1.30
sky2: used fixed RSS key
sky2: reduce default Tx ring size
sky2: rename up/down functions
sky2: pci posting issues
sky2: fix hang on shutdown (and other irq issues)
r6040: fix check against MCRO_HASHEN bit in r6040_multicast_list
MAINTAINERS: change email address for shemminger
pch_gbe: Move #include of module.h
... -
* 'kvm-updates/3.2' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM guest: prevent tracing recursion with kvmclock
Revert "KVM: PPC: Add support for explicit HIOR setting"
KVM: VMX: Check for automatic switch msr table overflow
KVM: VMX: Add support for guest/host-only profiling
KVM: VMX: add support for switching of PERF_GLOBAL_CTRL
KVM: s390: announce SYNC_MMU
KVM: s390: Fix tprot locking
KVM: s390: handle SIGP sense running intercepts
KVM: s390: Fix RUNNING flag misinterpretation -
* 'fixes' of http://ftp.arm.linux.org.uk/pub/linux/arm/kernel/git-cur/linux-2.6-arm:
ARM: wire up process_vm_writev and process_vm_readv syscalls
ARM: 7160/1: setup: avoid overflowing {elf,arch}_name from proc_info_list
ARM: 7158/1: add new MFP implement for NUC900
ARM: 7157/1: fix a building WARNING for nuc900
ARM: 7156/1: l2x0: fix compile error on !CONFIG_USE_OF
ARM: 7155/1: arch.h: Declare 'pt_regs' locally
ARM: 7154/1: mach-bcmring: fix build error in dma.c
ARM: 7153/1: mach-bcmring: fix build error in core.c
ARM: 7152/1: distclean: Remove generated .dtb files
ARM: 7150/1: Allow kernel unaligned accesses on ARMv6+ processors
ARM: 7149/1: spi/pl022: Enable clock in probe
Revert "ARM: 7098/1: kdump: copy kernel relocation code at the kexec prepare stage" -
* 'pm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
PM / Suspend: Fix bug in suspend statistics update
PM / Hibernate: Fix the early termination of test modes
PM / shmobile: Fix build of sh7372_pm_init() for CONFIG_PM unset
PM Sleep: Do not extend wakeup paths to devices with ignore_children set
PM / driver core: disable device's runtime PM during shutdown
PM / devfreq: correct Kconfig dependency
PM / devfreq: fix use after free in devfreq_remove_device
PM / shmobile: Avoid restoring the INTCS state during initialization
PM / devfreq: Remove compiler error after irq.h update
PM / QoS: Properly use the WARN() macro in dev_pm_qos_add_request()
PM / Clocks: Only disable enabled clocks in pm_clk_suspend()
ARM: mach-shmobile: sh7372 A3SP no_suspend_console fix
PM / shmobile: Don't skip debugging output in pd_power_up()
20 Nov, 2011
2 commits
-
Prevent tracing of preempt_disable() in get_cpu_var() in
kvm_clock_read(). When CONFIG_DEBUG_PREEMPT is enabled,
preempt_disable/enable() are traced and this causes the function_graph
tracer to go into an infinite recursion. By open coding the
preempt_disable() around the get_cpu_var(), we can use the notrace
version which prevents preempt_disable/enable() from being traced and
prevents the recursion.Based on a similar patch for Xen from Jeremy Fitzhardinge.
Tested-by: Gleb Natapov
Acked-by: Steven Rostedt
Signed-off-by: Avi Kivity -
* 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging:
hwmon: (exynos4_tmu) Fix Kconfig dependency[ Merging code in-flight, just because I can. What timezone should I
use? - Linus ]
19 Nov, 2011
11 commits
-
After commit 2a77c46de1e3dace73745015635ebbc648eca69c
(PM / Suspend: Add statistics debugfs file for suspend to RAM)
a missing pair of braces inside the state_store() function causes even
invalid arguments to suspend to be wrongly treated as failed suspend
attempts. Fix this.[rjw: Put the hash/subject of the buggy commit into the changelog.]
Signed-off-by: Srivatsa S. Bhat
Signed-off-by: Rafael J. Wysocki -
No longer at Citrix, still interested in Xen.
Signed-off-by: Jeremy Fitzhardinge
Cc: Jeremy Fitzhardinge
Signed-off-by: Linus Torvalds -
Dummy, non-zero definitions for HPAGE_MASK and HPAGE_SIZE were added in
51c6f666fceb ("mm: ZAP_BLOCK causes redundant work") to avoid a divide
by zero in generic kernel code.That code has since been removed, but probably should never have been
added in the first place: we don't want HPAGE_SIZE to act like PAGE_SIZE
for code that is working with hugepages, for example, when the
dependency on CONFIG_HUGETLB_PAGE has not been fulfilled.Because hugepage size can differ from architecture to architecture, each
is required to have their own definitions for both HPAGE_MASK and
HPAGE_SIZE. This is always done in arch/*/include/asm/page.h.So, just remove the dummy and dangerous definitions since they are no
longer needed and reveals the correct dependencies. Tested on
architectures using the definitions with allyesconfig: x86 (even with
thp), hppa, mips, powerpc, s390, sh3, sh4, sparc, and sparc64, and with
defconfig on ia64.Signed-off-by: David Rientjes
Signed-off-by: Linus Torvalds -
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
new helper: mount_subtree()
switch create_mnt_ns() to saner calling conventions, fix double mntput() in nfs
btrfs: fix double mntput() in mount_subvol() -
* 'for-linus' of git://oss.sgi.com/xfs/xfs:
MAINTAINERS: update XFS maintainer entry
xfs: use doalloc flag in xfs_qm_dqattach_one() -
* 'for-3.2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: Replace Paul Menage with Tejun Heo as cgroups maintainer -
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
random: Fix handing of arch_get_random_long in get_random_bytes()
x86: Call stop_machine_text_poke() on all CPUs
x86, ioapic: Only print ioapic debug information for IRQs belonging to an ioapic chip
x86/mrst: Avoid reporting wrong nmi status
x86/mrst: Add support for Penwell clock calibration
x86/apic: Allow use of lapic timer early calibration result
x86/apic: Do not clear nr_irqs_gsi if no legacy irqs
x86/platform: Add a wallclock_init func to x86_platforms ops
x86/mce: Make mce_chrdev_ops 'static const' -
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/ide:
cy82c693: fix PCI device selection
icside: DMA support fix
IDE: Don't powerdown Compaq Triflex IDE device on suspend
piix: ICH7 MWDMA1 errata -
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc:
sparc64: Patch sun4v code sequences properly on module load.
sparc: Kill custom io_remap_pfn_range().
sparc: Stash orig_i0 into %g6 instead of %g2
sparc: Fix handling of orig_i0 wrt. debugging when restarting syscalls.
sparc: sigutil: Include -
As is probably painfully obvious, I don't have time to be a cgroups
maintainer. Rather than have me continue to hope that I'll magically
find more spare time, instead Tejun has kindly agreed to take over the
role, along with Li Zefan.-tj: added cgroup tree URL to MAINTAINERS file
Signed-off-by: Paul Menage
Acked-by: Li Zefan
Signed-off-by: Tejun Heo
LKML-Reference: -
Commit 2aede851ddf08666f68ffc17be446420e9d2a056
(PM / Hibernate: Freeze kernel threads after preallocating memory)
postponed the freezing of kernel threads to after preallocating memory
for hibernation. But while doing that, the hibernation test TEST_FREEZER
and the test mode HIBERNATION_TESTPROC were not moved accordingly.As a result, when using these test modes, it only goes upto the freezing of
userspace and exits, when in fact it should go till the complete end of task
freezing stage, namely the freezing of kernel threads as well.So, move these points of exit to appropriate places so that freezing of
kernel threads is also tested while using these test harnesses.Signed-off-by: Srivatsa S. Bhat
Signed-off-by: Rafael J. Wysocki
