On Fri, Mar 29, 2013 at 07:27:06PM -0700, Tejun Heo wrote:
> Both dump_stack() and show_stack() are currently implemented by each
> architecture. show_stack(NULL, NULL) dumps the backtrace for the
> current task as does dump_stack(). On some archs, dump_stack() prints
> extra information - pid, utsname and so on - in addition to the
> backtrace while the two are identical on other archs.
>
> The usages in arch-independent code of the two functions indicate
> show_stack(NULL, NULL) should print out bare backtrace while
> dump_stack() is used for debugging purposes when something went wrong,
> so it does make sense to print additional information on the task
> which triggered dump_stack().
>
> There's no reason to require archs to implement two separate but
> mostly identical functions. It leads to unnecessary subtle
> differences among archs and makes it very tedius to add generic debug
> information.
>
> This patch expands the dummy fallback dump_stack() implementation in
> lib/dump_stack.c such that it prints out debug information (taken from
> x86) and invokes show_stack(NULL, NULL) and drops arch-specific
> dump_stack() implementations in all archs except blackfin and s390.
> Blackfin's dump_stack() does something wonky that I don't understand
> and s390 prints its own debug information which includes fields which
> aren't accessible from arch-indepdent code.
>
> Debug information can be printed separately by calling
> dump_stack_print_info() so that arch-specific dump_stack()
> implementation can still emit the same debug information. This is
> used in blackfin.
>
> This patch brings the following behavior changes.
>
> * On some archs, an extra level in backtrace for show_stack() could be
> printed. This is because the top frame was determined in
> dump_stack() on those archs while generic dump_stack() can't do that
> reliably. It can be compensated by inlining dump_stack() but not
> sure whether that'd be necessary.
>
> * Most archs didn't use to print debug info on dump_stack(). They do
> now.
>
> An example WARN dump follows.
>
> WARNING: at /work/os/work/kernel/workqueue.c:4840 init_workqueues+0x35/0x505()
> Hardware name: empty
> Modules linked in:
> Pid: 1, comm: swapper/0 Not tainted 3.9.0-rc1-work+ #17
> 0000000000000009 ffff88007c861e08 ffffffff81c61545 ffff88007c861e48
> ffffffff8108f50f ffffffff82228240 0000000000000040 ffffffff8234a03c
> 0000000000000000 0000000000000000 0000000000000000 ffff88007c861e58
> Call Trace:
> [<ffffffff81c61545>] dump_stack+0x19/0x1b
> [<ffffffff8108f50f>] warn_slowpath_common+0x7f/0xc0
> [<ffffffff8108f56a>] warn_slowpath_null+0x1a/0x20
> [<ffffffff8234a071>] init_workqueues+0x35/0x505
> ...
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: linux-s390@xxxxxxxxxxxxxxx
> Cc: Mike Frysinger <vapier@xxxxxxxxxx>
> Cc: uclinux-dist-devel@xxxxxxxxxxxxxxxxxxxx
For the CRIS bits:
Acked-by: Jesper Nilsson <jesper.nilsson@xxxxxxxx>
/^JN - Jesper Nilsson
--
Jesper Nilsson -- jesper.nilsson@xxxxxxxx
--
To unsubscribe from this list: send the line "unsubscribe linux-arch" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
