Messages in this thread | | | Date | Sat, 06 Oct 2012 17:06:27 +0800 | From | Michael Wang <> | Subject | Re: [PATCH] sched: fix should_resched() to avoid do schedule in atomic |
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On 09/26/2012 11:41 AM, Michael Wang wrote: > On 09/18/2012 11:13 AM, Michael Wang wrote: >> This patch try to fix the BUG: >> >> [ 0.043953] BUG: scheduling while atomic: swapper/0/1/0x10000002 >> [ 0.044017] no locks held by swapper/0/1. >> [ 0.044692] Pid: 1, comm: swapper/0 Not tainted 3.6.0-rc1-00420-gb7aebb9 #34 >> [ 0.045861] Call Trace: >> [ 0.048071] [<c106361e>] __schedule_bug+0x5e/0x70 >> [ 0.048890] [<c1b28701>] __schedule+0x91/0xb10 >> [ 0.049660] [<c14472ea>] ? vsnprintf+0x33a/0x450 >> [ 0.050444] [<c1060006>] ? lg_local_lock+0x6/0x70 >> [ 0.051256] [<c14fb5b1>] ? wait_for_xmitr+0x31/0x90 >> [ 0.052019] [<c144fd55>] ? do_raw_spin_unlock+0xa5/0xf0 >> [ 0.052903] [<c1b2a532>] ? _raw_spin_unlock+0x22/0x30 >> [ 0.053759] [<c105cdbb>] ? up+0x1b/0x70 >> [ 0.054421] [<c1065d6b>] __cond_resched+0x1b/0x30 >> [ 0.055228] [<c1b292d5>] _cond_resched+0x45/0x50 >> [ 0.056020] [<c1b26c58>] mutex_lock_nested+0x28/0x370 >> [ 0.056884] [<c1034222>] ? console_unlock+0x3a2/0x4e0 >> [ 0.057741] [<c1ac8559>] __irq_alloc_descs+0x39/0x1c0 >> [ 0.058589] [<c10223bc>] io_apic_setup_irq_pin+0x2c/0x310 >> [ 0.060042] [<c20638df>] setup_IO_APIC+0x101/0x744 >> [ 0.060878] [<c1021d51>] ? clear_IO_APIC+0x31/0x50 >> [ 0.061695] [<c20600f4>] native_smp_prepare_cpus+0x538/0x680 >> [ 0.062644] [<c2056a91>] ? do_one_initcall+0x12c/0x12c >> [ 0.063517] [<c2056a91>] ? do_one_initcall+0x12c/0x12c >> [ 0.064016] [<c2056adc>] kernel_init+0x4b/0x17f >> [ 0.064790] [<c2056a91>] ? do_one_initcall+0x12c/0x12c >> [ 0.065660] [<c1b2bbd6>] kernel_thread_helper+0x6/0x10 >> >> The process to trigger the BUG is: >> >> native_smp_prepare_cpus() >> preempt_disable() //preempt_count++ >> __irq_alloc_descs() >> mutex_lock() >> might_sleep() //should_resched() return true >> __schedule() >> preempt_disable() //preempt_count++ >> schedule_bug() //preempt_count > 1, report bug >> >> So the issue is that should_resched() should not return true while the preempt >> already disabled. > > Hi, Peter > > Could we use this solution to fix the bug?
Please tell me if it's wrong, I really want to help fix it.
Regards, Michael Wang
> > Regards, > Michael Wang > >> >> This patch will fix the issue, then might_sleep() won't do schedule in atomic >> any more. >> >> Reported-by: Fengguang Wu <wfg@linux.intel.com> >> Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com> >> --- >> kernel/sched/core.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index b38f00e..2b7cd15 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -4171,7 +4171,7 @@ SYSCALL_DEFINE0(sched_yield) >> >> static inline int should_resched(void) >> { >> - return need_resched() && !(preempt_count() & PREEMPT_ACTIVE); >> + return need_resched() && !preempt_count(); >> } >> >> static void __cond_resched(void) >> >
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