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Subjectalpha bug in signal handling
On Tue, Dec 04, 2001 at 06:15:50PM -0800, David Mosberger wrote:
> Oh, sorry, I was referring to teh *other* problem... ;-)
>
> What I meant is that the check for re-scheduling
> (current->need_resched) and signal deliverify (current->sigpending)
> needs to be done with interrupts turned off, and the interrupts need
> to be left off until user space is reached. Otherwise, you could get
> an interrupt which would wake up a higher priority task or post a
> signal between the check and the return to user space.
>
> I didn't see this interrupt disabling in the Alpha version of entry.S,
> but I have to admit my Alpha assembly is getting quite rusty.

Oh, yes, I see. This should fix it.


r~



--- arch/alpha/kernel/entry.S.orig Tue Dec 4 18:40:53 2001
+++ arch/alpha/kernel/entry.S Tue Dec 4 18:46:33 2001
@@ -580,6 +580,10 @@
and $0,8,$0
beq $0,restore_all
ret_from_reschedule:
+ /* Turn off interrupts so that resched and signal delivery
+ checks are done atomically. */
+ addq $31,7,$16
+ call_pal PAL_swpipl
ldq $2,TASK_NEED_RESCHED($8)
lda $4,init_task_union
bne $2,reschedule
-
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