07 Jun, 2015
1 commit
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preempt_schedule_context() is a tracing safe preemption point but it's
only used when CONFIG_CONTEXT_TRACKING=y. Other configs have tracing
recursion issues since commit:b30f0e3ffedf ("sched/preempt: Optimize preemption operations on __schedule() callers")
introduced function based preemp_count_*() ops.
Lets make it available on all configs and give it a more appropriate
name for its new position.Reported-by: Fengguang Wu
Signed-off-by: Frederic Weisbecker
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1433432349-1021-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar
28 Oct, 2014
1 commit
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task_preempt_count() is pointless if preemption counter is per-cpu,
currently this is x86 only. It is only valid if the task is not
running, and even in this case the only info it can provide is the
state of PREEMPT_ACTIVE bit.Change its single caller to check p->on_rq instead, this should be
the same if p->state != TASK_RUNNING, and kill this helper.Signed-off-by: Oleg Nesterov
Signed-off-by: Peter Zijlstra (Intel)
Cc: Steven Rostedt
Cc: Kirill Tkhai
Cc: Alexander Graf
Cc: Andrew Morton
Cc: Arnd Bergmann
Cc: Christoph Lameter
Cc: Linus Torvalds
Cc: linux-arch@vger.kernel.org
Link: http://lkml.kernel.org/r/20141008183348.GC17495@redhat.com
Signed-off-by: Ingo Molnar
11 Dec, 2013
1 commit
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While hunting a preemption issue with Alexander, Ben noticed that the
currently generic PREEMPT_NEED_RESCHED stuff is horribly broken for
load-store architectures.We currently rely on the IPI to fold TIF_NEED_RESCHED into
PREEMPT_NEED_RESCHED, but when this IPI lands while we already have
a load for the preempt-count but before the store, the store will erase
the PREEMPT_NEED_RESCHED change.The current preempt-count only works on load-store archs because
interrupts are assumed to be completely balanced wrt their preempt_count
fiddling; the previous preempt_count load will match the preempt_count
state after the interrupt and therefore nothing gets lost.This patch removes the PREEMPT_NEED_RESCHED usage from generic code and
pushes it into x86 arch code; the generic code goes back to relying on
TIF_NEED_RESCHED.Boot tested on x86_64 and compile tested on ppc64.
Reported-by: Benjamin Herrenschmidt
Reported-and-Tested-by: Alexander Graf
Signed-off-by: Peter Zijlstra
Cc: Linus Torvalds
Link: http://lkml.kernel.org/r/20131128132641.GP10022@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar
28 Sep, 2013
1 commit
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Yuanhan reported a serious throughput regression in his pigz
benchmark. Using the ftrace patch I found that several idle
paths need more TLC before we can switch the generic
need_resched() over to preempt_need_resched.The preemption paths benefit most from preempt_need_resched and
do indeed use it; all other need_resched() users don't really
care that much so reverting need_resched() back to
tif_need_resched() is the simple and safe solution.Reported-by: Yuanhan Liu
Signed-off-by: Peter Zijlstra
Cc: Fengguang Wu
Cc: Huang Ying
Cc: lkp@linux.intel.com
Cc: Linus Torvalds
Link: http://lkml.kernel.org/r/20130927153003.GF15690@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar
25 Sep, 2013
4 commits
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Remove the bloat of the C calling convention out of the
preempt_enable() sites by creating an ASM wrapper which allows us to
do an asm("call ___preempt_schedule") instead.calling.h bits by Andi Kleen
Suggested-by: Linus Torvalds
Signed-off-by: Peter Zijlstra
Link: http://lkml.kernel.org/n/tip-tk7xdi1cvvxewixzke8t8le1@git.kernel.org
[ Fixed build error. ]
Signed-off-by: Ingo Molnar -
Rewrite the preempt_count macros in order to extract the 3 basic
preempt_count value modifiers:__preempt_count_add()
__preempt_count_sub()and the new:
__preempt_count_dec_and_test()
And since we're at it anyway, replace the unconventional
$op_preempt_count names with the more conventional preempt_count_$op.Since these basic operators are equivalent to the previous _notrace()
variants, do away with the _notrace() versions.Signed-off-by: Peter Zijlstra
Link: http://lkml.kernel.org/n/tip-ewbpdbupy9xpsjhg960zwbv8@git.kernel.org
Signed-off-by: Ingo Molnar -
We need a few special preempt_count accessors:
- task_preempt_count() for when we're interested in the preemption
count of another (non-running) task.
- init_task_preempt_count() for properly initializing the preemption
count.
- init_idle_preempt_count() a special case of the above for the idle
threads.With these no generic code ever touches thread_info::preempt_count
anymore and architectures could choose to remove it.Signed-off-by: Peter Zijlstra
Link: http://lkml.kernel.org/n/tip-jf5swrio8l78j37d06fzmo4r@git.kernel.org
Signed-off-by: Ingo Molnar -
In order to prepare to per-arch implementations of preempt_count move
the required bits into an asm-generic header and use this for all
archs.Signed-off-by: Peter Zijlstra
Link: http://lkml.kernel.org/n/tip-h5j0c1r3e3fk015m30h8f1zx@git.kernel.org
Signed-off-by: Ingo Molnar