Ping, this problem still persists in v3.7-rc6. Could someone have a look? On Sat, Nov 10, 2012 at 06:32:28AM +0100, Hannes Frederic Sowa wrote: > Following RCU warning showed up while executing a shebang-script under > perf-record (could even be an empty script) on a 3.7-rc4 stable kernel: > > [ 32.185108] > [ 32.185332] =============================== > [ 32.185602] [ INFO: suspicious RCU usage. ] > [ 32.185903] 3.7.0-rc4 #1 Not tainted > [ 32.186021] ------------------------------- > [ 32.186021] include/linux/cgroup.h:566 suspicious > rcu_dereference_check() usage! > [ 32.186021] > [ 32.186021] other info that might help us debug this: > [ 32.186021] > [ 32.186021] > [ 32.186021] rcu_scheduler_active = 1, debug_locks = 0 > [ 32.186021] 1 lock held by empty.sh/556: > [ 32.186021] #0: (&sig->cred_guard_mutex){+.+.+.}, at: > [<ffffffff811d1d16>] prepare_bprm_creds+0x36/0x80 > [ 32.186021] > [ 32.186021] stack backtrace: > [ 32.186021] Pid: 556, comm: empty.sh Not tainted 3.7.0-rc4 #1 > [ 32.186021] Call Trace: > [ 32.186021] [<ffffffff810d336d>] lockdep_rcu_suspicious+0xfd/0x130 > [ 32.186021] [<ffffffff81153de6>] perf_event_comm+0x436/0x610 > [ 32.186021] [<ffffffff810d181d>] ? trace_hardirqs_off+0xd/0x10 > [ 32.186021] [<ffffffff810ac37f>] ? local_clock+0x6f/0x80 > [ 32.186021] [<ffffffff810d217f>] ? > lock_release_holdtime.part.26+0xf/0x180 > [ 32.186021] [<ffffffff811d1bd3>] set_task_comm+0x73/0x180 > [ 32.186021] [<ffffffff811d24ba>] setup_new_exec+0x9a/0x210 > [ 32.186021] [<ffffffff81225cf3>] load_elf_binary+0x3e3/0x1ab0 > [ 32.186021] [<ffffffff810ac0f5>] ? sched_clock_local+0x25/0xa0 > [ 32.186021] [<ffffffff810ac298>] ? sched_clock_cpu+0xa8/0x120 > [ 32.186021] [<ffffffff810d181d>] ? trace_hardirqs_off+0xd/0x10 > [ 32.186021] [<ffffffff810ac37f>] ? local_clock+0x6f/0x80 > [ 32.186021] [<ffffffff81225910>] ? load_elf_library+0x240/0x240 > [ 32.186021] [<ffffffff81225910>] ? load_elf_library+0x240/0x240 > [ 32.186021] [<ffffffff811d14a4>] search_binary_handler+0x194/0x4f0 > [ 32.186021] [<ffffffff811d136f>] ? search_binary_handler+0x5f/0x4f0 > [ 32.186021] [<ffffffff81225220>] ? compat_sys_ioctl+0x1510/0x1510 > [ 32.186021] [<ffffffff812254b4>] load_script+0x294/0x2c0 > [ 32.186021] [<ffffffff810d217f>] ? > lock_release_holdtime.part.26+0xf/0x180 > [ 32.186021] [<ffffffff81225220>] ? compat_sys_ioctl+0x1510/0x1510 > [ 32.186021] [<ffffffff811d14a4>] search_binary_handler+0x194/0x4f0 > [ 32.186021] [<ffffffff811d136f>] ? search_binary_handler+0x5f/0x4f0 > [ 32.186021] [<ffffffff811d22cb>] do_execve_common.isra.25+0x50b/0x5b0 > [ 32.186021] [<ffffffff811d1eea>] ? do_execve_common.isra.25+0x12a/0x5b0 > [ 32.186021] [<ffffffff811d238b>] do_execve+0x1b/0x20 > [ 32.186021] [<ffffffff811d26c4>] sys_execve+0x54/0x80 > [ 32.186021] [<ffffffff816d8f99>] stub_execve+0x69/0xc0 > > I think this dereference qualifies for the task_lock exception (as noted > in kernel/cgroup.c), thus this patch ensures calling perf_event_comm > before giving up the task_lock. > > Changelog -v2 (since <20121103235758.gd18...@order.stressinduktion.org>): > 1) rebased to 3.7-rc4 > 2) slightly improved/updated commit msg and added more people to Cc > > Cc: Peter Zijlstra <a.p.zijls...@chello.nl> > Cc: Paul Mackerras <pau...@samba.org> > Cc: Ingo Molnar <mi...@redhat.com> > Cc: Arnaldo Carvalho de Melo <a...@ghostprotocols.net> > Signed-off-by: Hannes Frederic Sowa <han...@stressinduktion.org> > --- > fs/exec.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/exec.c b/fs/exec.c > index 0039055..a961b9d 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1038,8 +1038,8 @@ void set_task_comm(struct task_struct *tsk, char *buf) > memset(tsk->comm, 0, TASK_COMM_LEN); > wmb(); > strlcpy(tsk->comm, buf, sizeof(tsk->comm)); > - task_unlock(tsk); > perf_event_comm(tsk); > + task_unlock(tsk); > } > > static void filename_to_taskname(char *tcomm, const char *fn, unsigned int > len) >
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