The patch titled
Subject: kernel/module.c: do a WARN_ON_ONCE() for assert module mutex not held
has been added to the -mm tree. Its filename is
module-do-a-warn_on_once-for-assert-module-mutex-not-held.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/module-do-a-warn_on_once-for-assert-module-mutex-not-held.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/module-do-a-warn_on_once-for-assert-module-mutex-not-held.patch
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From: Steven Rostedt <rostedt@xxxxxxxxxxx>
Subject: kernel/module.c: do a WARN_ON_ONCE() for assert module mutex not held
When running with lockdep enabled, I triggered the WARN_ON() in the module
code that asserts when module_mutex or rcu_read_lock_sched are not held.
The issue I have is that this can also be called from the dump_stack()
code, causing us to enter an infinite loop...
------------[ cut here ]------------
WARNING: CPU: 1 PID: 0 at kernel/module.c:268 module_assert_mutex_or_preempt+0x3c/0x3e
Modules linked in: ip6t_REJECT nf_reject_ipv6 nf_conntrack_ipv6
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.7.0-rc3-test-00013-g501c2375253c #14
Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014
ffff880215e8fa70 ffff880215e8fa70 ffffffff812fc8e3 0000000000000000
ffffffff81d3e55b ffff880215e8fac0 ffffffff8104fc88 ffffffff8104fcab
0000000915e88300 0000000000000046 ffffffffa019b29a 0000000000000001
Call Trace:
[<ffffffff812fc8e3>] dump_stack+0x67/0x90
[<ffffffff8104fc88>] __warn+0xcb/0xe9
[<ffffffff8104fcab>] ? warn_slowpath_null+0x5/0x1f
------------[ cut here ]------------
WARNING: CPU: 1 PID: 0 at kernel/module.c:268 module_assert_mutex_or_preempt+0x3c/0x3e
Modules linked in: ip6t_REJECT nf_reject_ipv6 nf_conntrack_ipv6
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.7.0-rc3-test-00013-g501c2375253c #14
Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014
ffff880215e8f7a0 ffff880215e8f7a0 ffffffff812fc8e3 0000000000000000
ffffffff81d3e55b ffff880215e8f7f0 ffffffff8104fc88 ffffffff8104fcab
0000000915e88300 0000000000000046 ffffffffa019b29a 0000000000000001
Call Trace:
[<ffffffff812fc8e3>] dump_stack+0x67/0x90
[<ffffffff8104fc88>] __warn+0xcb/0xe9
[<ffffffff8104fcab>] ? warn_slowpath_null+0x5/0x1f
------------[ cut here ]------------
WARNING: CPU: 1 PID: 0 at kernel/module.c:268 module_assert_mutex_or_preempt+0x3c/0x3e
Modules linked in: ip6t_REJECT nf_reject_ipv6 nf_conntrack_ipv6
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.7.0-rc3-test-00013-g501c2375253c #14
Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014
ffff880215e8f4d0 ffff880215e8f4d0 ffffffff812fc8e3 0000000000000000
ffffffff81d3e55b ffff880215e8f520 ffffffff8104fc88 ffffffff8104fcab
0000000915e88300 0000000000000046 ffffffffa019b29a 0000000000000001
Call Trace:
[<ffffffff812fc8e3>] dump_stack+0x67/0x90
[<ffffffff8104fc88>] __warn+0xcb/0xe9
[<ffffffff8104fcab>] ? warn_slowpath_null+0x5/0x1f
------------[ cut here ]------------
WARNING: CPU: 1 PID: 0 at kernel/module.c:268 module_assert_mutex_or_preempt+0x3c/0x3e
[...]
Which gives us rather useless information. Worse yet, there's some race
that causes this, and I seldom trigger it, so I have no idea what
happened.
This would not be an issue if that warning was a WARN_ON_ONCE().
Link: http://lkml.kernel.org/r/20160712091550.30ddfff7@xxxxxxxxxxxxxxxxxx
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/module.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN kernel/module.c~module-do-a-warn_on_once-for-assert-module-mutex-not-held kernel/module.c
--- a/kernel/module.c~module-do-a-warn_on_once-for-assert-module-mutex-not-held
+++ a/kernel/module.c
@@ -264,7 +264,7 @@ static void module_assert_mutex_or_preem
if (unlikely(!debug_locks))
return;
- WARN_ON(!rcu_read_lock_sched_held() &&
+ WARN_ON_ONCE(!rcu_read_lock_sched_held() &&
!lockdep_is_held(&module_mutex));
#endif
}
_
Patches currently in -mm which might be from rostedt@xxxxxxxxxxx are
module-do-a-warn_on_once-for-assert-module-mutex-not-held.patch
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