On Tue, 2002-07-23 at 16:28, Ingo Molnar wrote:
> this is most definitely not the correct fix ...
>
> i'm quite convinced that the fix is to avoid illegal preemption, not to
> work it around.
I am not sure I am fully convinced one way or the other, but treating
every bit of code as we find it scares me. The fact is, if a
spin_unlock() can magically reenable interrupts that is a bug.
I don't like relying on chance and the possibility your debug tool found
the problem... but at the same time, Ingo's solution is a lot cleaner.
Linus, Ingo, comments?
Attached is the patch George mentioned, against 2.5.27.
Robert Love
diff -urN linux-2.5.27/include/asm-i386/system.h linux/include/asm-i386/system.h
--- linux-2.5.27/include/asm-i386/system.h Sat Jul 20 12:11:05 2002
+++ linux/include/asm-i386/system.h Tue Jul 23 18:03:47 2002
@@ -270,6 +270,13 @@
/* Compiling for a 386 proper. Is it worth implementing via cli/sti? */
#endif
+#define MASK_IF 0x200
+#define interrupts_enabled() ({ \
+ int flg; \
+ __save_flags(flg); \
+ flg & MASK_IF; \
+})
+
/*
* Force strict CPU ordering.
* And yes, this is required on UP too when we're talking
diff -urN linux-2.5.27/kernel/sched.c linux/kernel/sched.c
--- linux-2.5.27/kernel/sched.c Sat Jul 20 12:11:11 2002
+++ linux/kernel/sched.c Tue Jul 23 18:02:13 2002
@@ -899,7 +899,7 @@
{
struct thread_info *ti = current_thread_info();
- if (unlikely(ti->preempt_count))
+ if (unlikely(ti->preempt_count || !interrupts_enabled()))
return;
need_resched:
-
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