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    SubjectRe: [PATCH] ARM: BUG() dies silently
    From
    You might try the generic bug patch and see if it also fixes this
    problem - Simon

    On Thu, Mar 31, 2011 at 1:15 PM, Omar Ramirez Luna <omar.ramirez@ti.com> wrote:
    > There are some cases where the code generated for BUG() results
    > into an infinite while loop without causing a null dereference,
    > this ends on a kernel being stuck on a loop and the user without
    > a clue of what happened.
    >
    > E.g.: lib/scatterlist.c : __sg_alloc_table
    >
    >        BUG_ON(nents > max_ents);
    >  438:   9a000000        bls     440 <__sg_alloc_table+0x20>
    >  43c:   eafffffe        b       43c <__sg_alloc_table+0x1c>
    >
    > Adding volatile makes the compiler to avoid optimizations on this
    > code, which makes the panic to occur:
    >
    >        BUG_ON(nents > max_ents);
    >  438:   9a000002        bls     448 <__sg_alloc_table+0x28>
    >  43c:   e3a03000        mov     r3, #0
    >  440:   e5833000        str     r3, [r3]
    >  444:   eafffffc        b       43c <__sg_alloc_table+0x1c>
    >
    > Seen with gnu/linux cs arm-2010q1-202 and arm2010.09-50.
    >
    > Signed-off-by: Omar Ramirez Luna <omar.ramirez@ti.com>
    > ---
    >
    > If needed I can change:
    > ./arch/arm/mach-clps711x/include/mach/io.h:
    >        #define __raw_readsb(p,d,l)  do { *(int *)0 = 0; } while (0)
    > ./arch/arm/mach-clps711x/include/mach/io.h:
    >        #define __raw_readsl(p,d,l)  do { *(int *)0 = 0; } while (0)
    > ./arch/arm/mach-clps711x/include/mach/io.h:
    >        #define __raw_writesb(p,d,l) do { *(int *)0 = 0; } while (0)
    > ./arch/arm/mach-clps711x/include/mach/io.h:
    >        #define __raw_writesl(p,d,l) do { *(int *)0 = 0; } while (0)
    > ./arch/arm/kernel/traps.c:      *(int *)0 = 0;
    >
    >
    >  arch/arm/include/asm/bug.h |    2 +-
    >  1 files changed, 1 insertions(+), 1 deletions(-)
    >
    > diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h
    > index 4d88425..a58d863 100644
    > --- a/arch/arm/include/asm/bug.h
    > +++ b/arch/arm/include/asm/bug.h
    > @@ -12,7 +12,7 @@ extern void __bug(const char *file, int line) __attribute__((noreturn));
    >  #else
    >
    >  /* this just causes an oops */
    > -#define BUG()          do { *(int *)0 = 0; } while (1)
    > +#define BUG()          do { *(volatile int *)0 = 0; } while(1)
    >
    >  #endif
    >
    > --
    > 1.7.1
    >
    > --
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