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SubjectRe: [PATCH v2] preempt: fix kernel build with !CONFIG_BKL
On Thu, Oct 28, 2010 at 04:12:33PM +0200, Arnd Bergmann wrote:
> The preempt count logic tries to take the BKL into account, which breaks
> when CONFIG_BKL is not set.
>
> Use the same preempt_count offset that we use without CONFIG_PREEMPT
> when CONFIG_BKL is disabled.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Reported-by: Kirill Shutemov <kirill@shutemov.name>
> ---
> > On Thursday 28 October 2010, Kirill A. Shutemov wrote:
> > On Thu, Oct 28, 2010 at 01:20:44PM +0200, Arnd Bergmann wrote:
> > > The preempt count logic tries to take the BKL into account, which breaks
> > > when CONFIG_BKL is not set.
> > >
> > > Use the same preempt_count offset that we use without CONFIG_PREEMPT
> > > when CONFIG_BKL is disabled.
> > >
> > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > > Reported-by: "Kirill A. Shutemov" <kirill@shutemov.name>
> >
> > Remove quotes, please.
>
> That would make it an invalid email address because of the dot. I left out
> the middle initial now, if that's better.

Hm... You are right. But this wasn't a problem before (see git log).
Let's leave it with quotes.

>
> > I've got a lot of __schedule_bug. Log attached.
>
> Ok. I really don't understand the preempt code all that well, let's
> hope that this one is right.
>
> Thanks for your patience and for your testing!

It's usable now.

I'm not sure if it connected or not:

[ 6001.589151] INFO: task awesome:26743 blocked for more than 120 seconds.
[ 6001.589159] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 6001.589166] awesome D 00000555 7040 26743 3789 0x00000000
[ 6001.589182] f19afe3c 00000046 5e569d25 00000555 c16ac7c0 f1ae0d40 c16ac7c0 c16ac7c0
[ 6001.589206] f1ae0fc0 00000000 c16ac7c0 00000000 00000555 f1ae0d40 f4d46dc0 f19aff00
[ 6001.589228] 7fffffff f1ae0d40 f19afe9c c1317ea5 00000002 00000001 00000000 c131c57b
[ 6001.589251] Call Trace:
[ 6001.589271] [<c1317ea5>] schedule_timeout+0x27/0xb8
[ 6001.589284] [<c131c57b>] ? sub_preempt_count+0x9/0x8e
[ 6001.589298] [<c105290d>] ? get_parent_ip+0xb/0x31
[ 6001.589307] [<c131c5f3>] ? sub_preempt_count+0x81/0x8e
[ 6001.589318] [<c13174d2>] wait_for_common+0xa0/0xef
[ 6001.589329] [<c1057c3c>] ? default_wake_function+0x0/0x12
[ 6001.589339] [<c13175c0>] wait_for_completion+0x17/0x19
[ 6001.589352] [<c109a136>] stop_one_cpu+0x59/0x7f
[ 6001.589361] [<c10579e6>] ? migration_cpu_stop+0x0/0x2d
[ 6001.589373] [<c1317463>] ? wait_for_common+0x31/0xef
[ 6001.589384] [<c1052e69>] sched_exec+0xa7/0xbb
[ 6001.589395] [<c1101e09>] do_execve+0xb7/0x24a
[ 6001.589407] [<c1030b84>] sys_execve+0x31/0x54
[ 6001.589418] [<c102b3ba>] ptregs_execve+0x12/0x18
[ 6001.589429] [<c1319d00>] ? syscall_call+0x7/0xb
[ 6001.589438] 1 lock held by awesome/26743:
[ 6001.589444] #0: (&sig->cred_guard_mutex){......}, at: [<c1100d1e>] prepare_bprm_creds+0x25/0x5a

I probably saw it previously on pre-2.6.37-rc1 with CONFIG_BKL=y.

>
> Arnd
>
> diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
> index 8a389b6..41cb31f 100644
> --- a/include/linux/hardirq.h
> +++ b/include/linux/hardirq.h
> @@ -96,11 +96,15 @@
> */
> #define in_nmi() (preempt_count() & NMI_MASK)
>
> -#if defined(CONFIG_PREEMPT)
> +#if defined(CONFIG_PREEMPT) && defined(CONFIG_BKL)
> # define PREEMPT_INATOMIC_BASE kernel_locked()
> -# define PREEMPT_CHECK_OFFSET 1
> #else
> # define PREEMPT_INATOMIC_BASE 0
> +#endif
> +
> +#if defined(CONFIG_PREEMPT)
> +# define PREEMPT_CHECK_OFFSET 1
> +#else
> # define PREEMPT_CHECK_OFFSET 0
> #endif
>

--
Kirill A. Shutemov


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