Messages in this thread | | | Date | Thu, 20 Dec 2007 16:40:00 -0800 | From | Andrew Morton <> | Subject | Re: Linux 2.6.24-rc5 x86 architecture no longer Oopses... |
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On Fri, 21 Dec 2007 01:30:35 +0100 Ingo Molnar <mingo@elte.hu> wrote:
> > * Andrew Morton <akpm@linux-foundation.org> wrote: > > > On Fri, 21 Dec 2007 00:47:59 +0100 > > Ingo Molnar <mingo@elte.hu> wrote: > > > > > > __raw_spin_lock(&die.lock); > > > > raw_local_save_flags(flags); > > > > - die.lock_owner = smp_processor_id(); > > > > + die.lock_owner = raw_smp_processor_id(); > > > > > > we just disabled irqs with raw_local_save_flags(). > > > > <chases x86 spaghetti for a while> > > > > raw_local_save_flags() doesn't disable interrupts? > > argh. Indeed! (I wanted us to fix that misleading name eons ago, to
The naming of those functions is truly awful and it goes back to year 0.
> *_save_flags_only(), but some stupid bikeshed painting discussion > prevented it from ever happening.)
local_read_flags().
> that should have been raw_local_irq_save(flags)!
So raw_local_save_flags() and raw_local_irq_save() have different semantics.
omigawd, what have we done?
> but ... why is it done like that? Why do we first take the die.lock and > disable interrupts afterwards? It's highly weird. 64-bit does it all > correctly in traps_64.c, so unification will help us out - but so far > perhaps the patch below we should do in 2.6.24? > > Ingo > > ------------> > Subject: x86: fix die() to not be preemptible > From: Ingo Molnar <mingo@elte.hu> > > Andrew "Eagle Eye" Morton noticed that we use raw_local_save_flags() > instead of raw_local_irq_save(flags) in die(). > > do it correctly - and first disable interrupts, then take the spinlock. > > Signed-off-by: Ingo Molnar <mingo@elte.hu> > --- > arch/x86/kernel/traps_32.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > Index: linux-x86.q/arch/x86/kernel/traps_32.c > =================================================================== > --- linux-x86.q.orig/arch/x86/kernel/traps_32.c > +++ linux-x86.q/arch/x86/kernel/traps_32.c > @@ -373,14 +373,13 @@ void die(const char * str, struct pt_reg > > if (die.lock_owner != raw_smp_processor_id()) { > console_verbose(); > + raw_local_irq_save(flags); > __raw_spin_lock(&die.lock); > - raw_local_save_flags(flags); > die.lock_owner = smp_processor_id(); > die.lock_owner_depth = 0; > bust_spinlocks(1); > - } > - else > - raw_local_save_flags(flags); > + } else > + raw_local_irq_save(flags); > > if (++die.lock_owner_depth < 3) { > unsigned long esp;
Looks sane.
I suppose there's some reason why we can't just use spin_lock_irqsave(). But that reason was either so obvious or so unimportant that a comment was not needed. Sigh.
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