* Jiri Kosina <[email protected]> wrote:
> On Wed, 6 Dec 2006, Ingo Molnar wrote:
>
> > i'll probably ack such a patch, it can be useful even when the line
> > number is unique: if someone reports a WARN_ON() from an old kernel i
> > dont have to dig up the exact source but can see it right from the
> > condition what happened. Useful redundancy in bug output can be quite
> > useful at times. Please post it and we'll see whether it's acceptable.
>
> OK, thanks, I will send it later today.
>
> BTW I still don't see how to distinguish it easily ... for example:
>
> WARNING at kernel/mutex.c:132 __mutex_lock_common()
> [<c0103d70>] dump_trace+0x68/0x1b5
> [<c0103ed5>] show_trace_log_lvl+0x18/0x2c
> [<c010445b>] show_trace+0xf/0x11
> [<c01044cd>] dump_stack+0x12/0x14
> [<c037523f>] __mutex_lock_slowpath+0xc6/0x261
> [<c0199c61>] create_dir+0x24/0x1ba
> [<c019a30b>] sysfs_create_dir+0x45/0x5f
> [<c01f302b>] kobject_add+0xd6/0x18d
> [<c01f31fb>] kobject_register+0x19/0x30
> [<c02e771a>] md_probe+0x11a/0x124
> [<c0267fa4>] kobj_lookup+0xe6/0x122
> [<c01ec12e>] get_gendisk+0xe/0x1b
> [<c018590e>] do_open+0x2e/0x298
> [<c0185d0f>] blkdev_open+0x25/0x4d
> [<c016451b>] __dentry_open+0xc3/0x17e
> [<c0164650>] nameidata_to_filp+0x24/0x33
> [<c0164691>] do_filp_open+0x32/0x39
> [<c01646da>] do_sys_open+0x42/0xbe
> [<c016478f>] sys_open+0x1c/0x1e
> [<c0102dbc>] syscall_call+0x7/0xb
>
> How can you see immediately which one of the two WARN_ONs in
> spin_lock_mutex() triggered?
yeah, i can tell that even without assembly or gdb, just from the
offset:
> [<c037523f>] __mutex_lock_slowpath+0xc6/0x261
there are 4 WARN_ON()s in __mutex_lock_slowpath(), distributed roughly
equally. Which makes the above one the second out of the four
WARN_ON()s, i.e.:
DEBUG_LOCKS_WARN_ON(l->magic != l); \
Did i get it right? (but then again i guess i've got an unfair advantage
in interpreting locking related bug messages ;-)
but it can also be told semantically, it cannot be the in_interrupt()
assert because this is clearly not IRQ context:
> [<c037523f>] __mutex_lock_slowpath+0xc6/0x261
> [<c0199c61>] create_dir+0x24/0x1ba
> [<c019a30b>] sysfs_create_dir+0x45/0x5f
but in such cases i'd rather suggest the use of inline functions instead
of macros and then it's a simple gdb lookup to figure out the call site.
So, which clown added that macro to mutex-debug.h ... oh, never mind.
Ingo
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