On Wed, 6 Dec 2006, Ingo Molnar wrote:
> a WARN_ON() also triggers a stack dump, which should pinpoint the exact
> location. (especially if combined with kallsyms) For example:
Actually, I was referring to something a little bit different. For example
kernel/mutex.c:__mutex_lock_common() calls spin_lock_mutex() on line 132.
spin_lock_mutex() contains
DEBUG_LOCKS_WARN_ON(in_interrupt()); \
local_irq_save(flags); \
__raw_spin_lock(&(lock)->raw_lock); \
DEBUG_LOCKS_WARN_ON(l->magic != l); \
When one of these two WARN_ONs trigger, we get only
WARNING at kernel/mutex.c:132 __mutex_lock_common()
but it's indistuingishable which of the two WARN_ONs triggered. My patch
turns this into
WARNING (l->magic != l) at kernel/mutex.c:132 __mutex_lock_common()
> side-effects happen regularly in WARN_ON()s and while they should be
> avoided, they are not noticed by the compiler and can cause nasty bugs
> if executed twice. Do we really need this change?
I absolutely don't insist on it to be merged, besides this Andrew also
pointed out non-trivial .text growth. I just cooked it up for myself when
debugging some locking problems and that warning at kernel/mutex.c:132
triggered, and I didn't know which one was the reason.
--
Jiri Kosina
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