diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2013-11-28 17:26:41 +0400 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2013-12-11 18:52:32 +0400 |
| commit | ba1f14fbe70965ae0fb1655a5275a62723f65b77 (patch) | |
| tree | 412534b605bf33e5e930172686dd4f31d157fc51 /include/linux/sched.h | |
| parent | 8e8339a3a1069141985daaa2521ba304509ddecd (diff) | |
| download | linux-ba1f14fbe70965ae0fb1655a5275a62723f65b77.tar.xz | |
sched: Remove PREEMPT_NEED_RESCHED from generic code
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 <benh@kernel.crashing.org>
Reported-and-Tested-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20131128132641.GP10022@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/sched.h')
| -rw-r--r-- | include/linux/sched.h | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 768b037dfacb..96d674ba3876 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -440,8 +440,6 @@ struct task_cputime { .sum_exec_runtime = 0, \ } -#define PREEMPT_ENABLED (PREEMPT_NEED_RESCHED) - #ifdef CONFIG_PREEMPT_COUNT #define PREEMPT_DISABLED (1 + PREEMPT_ENABLED) #else |