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Author SHA1 Message Date
Peter Zijlstra cee34d88ca lockdep: Fix a race between /proc/lock_stat and module unload 
The lock_class iteration of /proc/lock_stat is not serialized against
the lockdep_free_key_range() call from module unload.

Therefore it can happen that we find a class of which ->name/->key are
no longer valid.

There is a further bug in zap_class() that left ->name dangling. Cure
this. Use RCU_INIT_POINTER() because NULL.

Since lockdep_free_key_range() is rcu_sched serialized, we can read
both ->name and ->key under rcu_read_lock_sched() (preempt-disable)
and be assured that if we observe a !NULL value it stays safe to use
for as long as we hold that lock.

If we observe both NULL, skip the entry.

Reported-by: Jerome Marchand <jmarchan@redhat.com>
Tested-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150602105013.GS3644@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2015-06-07 15:46:30 +02:00
Peter Zijlstra 838cc7b488 lockdep/proc: Fix lock-time avg computation 
>    kernel/locking/lockdep_proc.c: In function 'seq_lock_time':
> >> kernel/locking/lockdep_proc.c:424:23: warning: comparison of distinct pointer types lacks a cast [enabled by default]
>
>    418	static void seq_lock_time(struct seq_file *m, struct lock_time *lt)
>    419	{
>    420		seq_printf(m, "%14lu", lt->nr);
>    421		seq_time(m, lt->min);
>    422		seq_time(m, lt->max);
>    423		seq_time(m, lt->total);
>  > 424		seq_time(m, lt->nr ? do_div(lt->total, lt->nr) : 0);
>    425	}

My compiler refuses to actually say that; but it looks wrong in that
do_div() returns the remainder, not the divisor.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Tested-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Link: http://lkml.kernel.org/r/20131106164230.GE16117@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2013-11-11 12:41:34 +01:00
Peter Zijlstra 8eddac3f10 locking: Move the lockdep code to kernel/locking/ 
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-wl7s3tta5isufzfguc23et06@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2013-11-06 07:55:08 +01:00