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Date: Tue, 2 Apr 2013 11:22:20 +0200 From: Jesper Nilsson <jesper.nilsson@...s.com> To: Tejun Heo <tj@...nel.org> Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, akpm@...ux-foundation.org, mingo@...hat.com, x86@...nel.org, rth@...ddle.net, linux@....linux.org.uk, msalter@...hat.com, starvik@...s.com, dhowells@...hat.com, tony.luck@...el.com, benh@...nel.crashing.org, takata@...ux-m32r.org, geert@...ux-m68k.org, james.hogan@...tec.com, monstr@...str.eu, ralf@...ux-mips.org, jonas@...thpole.se, rkuo@...eaurora.org, schwidefsky@...ibm.com, liqin.chen@...plusct.com, davem@...emloft.net, lethal@...ux-sh.org, vgupta@...opsys.com, chris@...kel.net, cmetcalf@...era.com, ysato@...rs.sourceforge.jp, gxt@...c.pku.edu.cn, jdike@...toit.com, Heiko Carstens <heiko.carstens@...ibm.com>, linux-s390@...r.kernel.org, Mike Frysinger <vapier@...too.org>, uclinux-dist-devel@...ckfin.uclinux.org Subject: Re: [PATCH 3/5] dump_stack: consolidate dump_stack() implementations and unify their behaviors 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@...nel.org> > Cc: Martin Schwidefsky <schwidefsky@...ibm.com> > Cc: Heiko Carstens <heiko.carstens@...ibm.com> > Cc: linux-s390@...r.kernel.org > Cc: Mike Frysinger <vapier@...too.org> > Cc: uclinux-dist-devel@...ckfin.uclinux.org For the CRIS bits: Acked-by: Jesper Nilsson <jesper.nilsson@...s.com> /^JN - Jesper Nilsson -- Jesper Nilsson -- jesper.nilsson@...s.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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