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?
Regards,
Michael Wang
>
> This patch will fix the issue, then might_sleep() won't do schedule in atomic
> any more.
>
> Reported-by: Fengguang Wu <w...@linux.intel.com>
> Signed-off-by: Michael Wang <wang...@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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