[PATCH] cpu: Defer smpboot kthread unparking until CPU known to scheduler

[PATCH] cpu: Defer smpboot kthread unparking until CPU known to scheduler

[Owen Hofmann]

Hi, this is a request to please include upstream commit
00df35f991914db6b8bde8cf09808e19a9cffc3d ("cpu: Defer smpboot kthread
unparking until CPU known to scheduler") in stable trees >= 3.15 and <
4.1.

Upstream dd9d3843755da95f63dd3a376f62b3e45c011210 ("sched: Fix
cpu_active_mask/cpu_online_mask race") was included in stable to fix a
race condition that led to kthreads running on the wrong cpu and
causing errors like "kernel BUG at kernel/smpboot.c:135!". This is
especially likely when running as a virtualized guest.

However, the fix depends on the ordering introduced in the requested
patch, so the issue remains in kernels between 3.15 when the bug was
introduced, and 4.1 which has 00df35f9.

Re: [PATCH] cpu: Defer smpboot kthread unparking until CPU known to scheduler

[Luis Henriques]

On Wed, Mar 16, 2016 at 05:38:05PM -0700, Owen Hofmann wrote:
> Hi, this is a request to please include upstream commit
> 00df35f991914db6b8bde8cf09808e19a9cffc3d ("cpu: Defer smpboot kthread
> unparking until CPU known to scheduler") in stable trees >= 3.15 and <
> 4.1.
> 
> Upstream dd9d3843755da95f63dd3a376f62b3e45c011210 ("sched: Fix
> cpu_active_mask/cpu_online_mask race") was included in stable to fix a
> race condition that led to kthreads running on the wrong cpu and
> causing errors like "kernel BUG at kernel/smpboot.c:135!". This is
> especially likely when running as a virtualized guest.
> 
> However, the fix depends on the ordering introduced in the requested
> patch, so the issue remains in kernels between 3.15 when the bug was
> introduced, and 4.1 which has 00df35f9.
> --
> To unsubscribe from this list: send the line "unsubscribe stable" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Thanks Owen, I'll queue this for the 3.16 kernel.

Cheers,
--
Lu�s