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author | Oleg Nesterov <oleg@redhat.com> | 2014-01-20 19:20:10 +0100 |
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committer | Ingo Molnar <mingo@kernel.org> | 2014-02-09 21:18:57 +0100 |
commit | 1b5ff816cab708ba44c7d7b56b613516269eb577 (patch) | |
tree | 999f1b9973ba0fe76ee3003124f7ac522873a08b /arch | |
parent | lockdep: Make held_lock->check and "int check" argument bool (diff) | |
download | linux-1b5ff816cab708ba44c7d7b56b613516269eb577.tar.xz linux-1b5ff816cab708ba44c7d7b56b613516269eb577.zip |
lockdep: Don't create the wrong dependency on hlock->check == 0
Test-case:
DEFINE_MUTEX(m1);
DEFINE_MUTEX(m2);
DEFINE_MUTEX(mx);
void lockdep_should_complain(void)
{
lockdep_set_novalidate_class(&mx);
// m1 -> mx -> m2
mutex_lock(&m1);
mutex_lock(&mx);
mutex_lock(&m2);
mutex_unlock(&m2);
mutex_unlock(&mx);
mutex_unlock(&m1);
// m2 -> m1 ; should trigger the warning
mutex_lock(&m2);
mutex_lock(&m1);
mutex_unlock(&m1);
mutex_unlock(&m2);
}
this doesn't trigger any warning, lockdep can't detect the trivial
deadlock.
This is because lock(&mx) correctly avoids m1 -> mx dependency, it
skips validate_chain() due to mx->check == 0. But lock(&m2) wrongly
adds mx -> m2 and thus m1 -> m2 is not created.
rcu_lock_acquire()->lock_acquire(check => 0) is fine due to read == 2,
so currently only __lockdep_no_validate__ can trigger this problem.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140120182010.GA26498@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
0 files changed, 0 insertions, 0 deletions