Re: [PATCH] semaphore: use raw_spin_lock_irq instead of raw_spin_lock_irqsave

[Ingo Molnar]

* Ingo Molnar <mingo@xxxxxxxxxx> wrote:

> 
> * Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
> 
> > The sleeping functions down, down_interruptible, down_killable and
> > down_timeout can't be called with interrupts disabled, so we don't have to
> > save and restore interrupt flag.
> > 
> > This patch avoids the costly pushf and popf instructions on the semaphore
> > path.
> > 
> > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> > 
> > ---
> >  kernel/locking/semaphore.c |   21 ++++++++-------------
> >  1 file changed, 8 insertions(+), 13 deletions(-)
> 
> I've applied this to the locking tree, I suspect we can do this on the condition 
> that it doesn't explode in early boot code (which has irqs disabled) and doesn't 
> generate early boot lockdep splats either.

Hm, this blew up pretty quick on a pretty regular x86-64 PC white-box, during 
early bootup:

  PANIC: early exception 0x08 IP 246:10 error ffffffff811537b2 cr2 0xffff88000240cff8

and I think it's due to your patch - verifying that now.

Thanks,

	Ingo