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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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