Messages in this thread | | | Subject | Re: mmotm 2010-04-05 - another RCU whinge (not network this time) | From | Valdis.Kletnieks@vt ... | Date | Fri, 09 Apr 2010 23:22:32 -0400 |
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On Fri, 09 Apr 2010 16:16:14 PDT, "Paul E. McKenney" said: > On Thu, Apr 08, 2010 at 07:57:28PM -0400, Valdis.Kletnieks@vt.edu wrote: > > On Mon, 05 Apr 2010 16:09:45 PDT, akpm@linux-foundation.org said: > > > The mm-of-the-moment snapshot 2010-04-05-16-09 has been uploaded to > > > > > > http://userweb.kernel.org/~akpm/mmotm/ > > > > Hit another one. I seem to be on a roll... > > > > Seen in dmesg, happened near end of the initrd.. > > > > [ 26.756864] > > [ 26.756866] =================================================== > > [ 26.756869] [ INFO: suspicious rcu_dereference_check() usage. ] > > [ 26.756871] --------------------------------------------------- > > [ 26.756874] fs/proc/array.c:241 invoked rcu_dereference_check() without protection! > > Color me confused. I cloned James Toy's git repository at > git://zen-kernel.org/kernel/mmotm.git, and gitk claims that I am on tag > 2010-04-05-16-09, which matches the string above. But when I look at > fs/proc/array.c near line 241, I see:
Andrew's -mm tree has 3 patches from Oleg Nesterov that hit that file, so the code is different from what you show. Color *me* confused why your clone of mmotm.git doesn't seem to contain them - I'm not sure how James Toy builds that git tree. Perhaps the tag is applied before those patches are - the 'mm.patch' that updates the Makefile with the version is usually in the *middle* of the 'series' file. What does HEAD of that tree look like?
My tree has:
/* needs ->siglock or rcu_read_lock() */ static void collect_sigign_sigcatch(struct task_struct *p, sigset_t *ign, sigset_t *catch) { struct sighand_struct *sighand = rcu_dereference(p->sighand);
And that rcu_dereference() does it.
Oleg, looks like proc-make-collect_sigign_sigcatch-rcu-safe.patch is the offender here, it added the line that causes the whinge.
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