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authorSteven Rostedt <rostedt@goodmis.org>2016-07-19 05:59:24 +0930
committerRusty Russell <rusty@rustcorp.com.au>2016-08-04 10:16:52 +0930
commit9502514f2808d29f6f2afa1c410e7808898dede1 (patch)
tree262778565727a00ca93362a120b9820869b3a4a5
parentb8612e517c3c9809e1200b72c474dbfd969e5a83 (diff)
module: 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(). Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r--kernel/module.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/module.c b/kernel/module.c
index 7f21ab238aa7..beaebea627ff 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -264,7 +264,7 @@ static void module_assert_mutex_or_preempt(void)
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
}