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powerpc: get_wchan(): solve possible race scenario due to parallel wakeup

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Add a check for p->state == TASK_RUNNING so that any wake-ups on
task_struct p in the interim lead to 0 being returned by get_wchan().

Signed-off-by: Kautuk Consul <kautuk.consul.1980@gmail.com>
[mpe: Confirmed other architectures do similar]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Kautuk Consul 2016-04-19 15:48:21 +05:30 committed by Michael Ellerman
parent 06755a8713
commit 4ca360f3db
1 changed files with 2 additions and 1 deletions
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3
arch/powerpc/kernel/process.c
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@ -1898,7 +1898,8 @@ unsigned long get_wchan(struct task_struct *p)
do {
sp = *(unsigned long *)sp;
if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD))
if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD) ||
p->state == TASK_RUNNING)
return 0;
if (count > 0) {
ip = ((unsigned long *)sp)[STACK_FRAME_LR_SAVE];