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| author | Steven Rostedt <rostedt@goodmis.org> | 2016-07-19 05:59:24 +0930 |
|---|---|---|
| committer | Rusty Russell <rusty@rustcorp.com.au> | 2016-08-04 10:16:52 +0930 |
| commit | 9502514f2808d29f6f2afa1c410e7808898dede1 (patch) | |
| tree | 262778565727a00ca93362a120b9820869b3a4a5 | |
| parent | b8612e517c3c9809e1200b72c474dbfd969e5a83 (diff) | |
| download | lwn-9502514f2808d29f6f2afa1c410e7808898dede1.tar.gz lwn-9502514f2808d29f6f2afa1c410e7808898dede1.zip | |
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.c | 2 |
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 } |