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SubjectRe: [patch] IDE problems on SMP, fixed? (fwd)

On Wed, 29 Jul 1998, Linus Torvalds wrote:

> Hanging in irq_enter() _tends_ to mean that the local CPU has done a
> global interrupt disable, and then enabled interrupts locally. BOOM. That
> would certainly cause lockups, although I don't see why this would be new
> behaviour: that would have been a lock-up problem since fairly long ago.
>
> This is fairly easy to check on: you can make "__sti" check that we don't
> have the global IRQ-lock enabled by doing something like

bingo. This caught the real bug, at some point we removed the 'extra'
sti() from run_task_queue(). Most code was fine but raid5.c not ... So
it's not an IDE problem after all. Maybe we should leave that check in
there for a few patchlevels? (patch attached) (my RAID5 SMP fixes will be
in the next RAID patchset)

best would be if we could somehow track this without runtime overhead ...
impossible i think :(

-- mingo

--- linux/include/asm-i386/system.h.orig Thu Jul 30 08:05:21 1998
+++ linux/include/asm-i386/system.h Thu Jul 30 09:24:58 1998
@@ -175,7 +175,13 @@
#define mb() __asm__ __volatile__ ("lock; addl $0,0(%%esp)": : :"memory")

/* interrupt control.. */
-#define __sti() __asm__ __volatile__ ("sti": : :"memory")
+#define GETEIP() ({ unsigned long eip; \
+ asm volatile("movl $1f,%0\n1:":"=g" (eip)); \
+ eip; })
+
+extern unsigned char global_irq_holder;
+
+#define __sti() do { if (global_irq_holder == current->processor) printk("__sti at %08lx\n", GETEIP()); __asm__ __volatile__ ("sti": : :"memory"); } while(0)
#define __cli() __asm__ __volatile__ ("cli": : :"memory")
#define __save_flags(x) \
__asm__ __volatile__("pushfl ; popl %0":"=g" (x): /* no input */ :"memory")

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