On 11/30/2012 10:52 AM, Vincent Palatin wrote:
> When a cpu enters S3 state, the FPU state is lost.
> After resuming for S3, if we try to lazy restore the FPU for a process running
> on the same CPU, this will result in a corrupted FPU context.
>
> We can just invalidate the "fpu_owner_task", so nobody will try to
> lazy restore a state which no longer exists in the hardware.
>
> Tested with a 64-bit kernel on a 4-core Ivybridge CPU with eagerfpu=off,
> by doing thousands of suspend/resume cycles with 4 processes doing FPU
> operations running. Without the patch, a process is killed after a
> few hundreds cycles by a SIGFPE.
>
> The issue seems to exist since 3.4 (after the FPU lazy restore was actually
> implemented),
> to apply the change to 3.4, "this_cpu_write" needs to be replaced by
> percpu_write.
>
> Cc: Duncan Laurie <dlau...@chromium.org>
> Cc: Olof Johansson <ol...@chromium.org>
> Cc: <sta...@kernel.org> [v3.4+] # for 3.4 need to replace this_cpu_write by
> percpu_write
> Signed-off-by: Vincent Palatin <vpala...@chromium.org>
Ouch! Thank you for catching this!
-hpa
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