Re: [PATCH 0/2] ipc/sem.c: sem_lock fixes

From: Andrew Morton
Date: Wed Jul 13 2016 - 18:05:36 EST

On Wed, 13 Jul 2016 07:06:50 +0200 Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> wrote:

> Hi Andrew, Hi Peter,
> next version of the sem_lock() fixes:
> The patches are again vs. tip.
> Patch 1 is ready for merging, Patch 2 is for review.
> - Patch 1 is the patch as in -next since January
> It fixes the race that was found by Felix.
> - Patch 2 removes the memory barriers that are part of the qspinlock
> code.
> - (The hysteresis patch would be patch 3. The risk of regressions
> can't be ruled out, thus it must wait for benchmarks from real
> workload tests)

I think you're saying that if these two patches cause performance
regressions, we will need ipc-sem-sem_lock-with-hysteresis.patch?

Is that even necessary? If your testing shows that
ipc-sem-sem_lock-with-hysteresis.patch makes things faster then in it
goes, surely?