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authorTrond Myklebust <trond.myklebust@primarydata.com>2014-06-05 11:31:01 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-10-05 14:52:20 -0700
commit0c99fc04f3d4f8a0731c2cc1b2b4d363542b9bbe (patch)
tree962ec73c496ee276f5078dc21c835662ba319834 /include
parent26935f7537395220e89ccab23b792862e8eacb09 (diff)
lockdep: Revert lockdep check in raw_seqcount_begin()
commit 22fdcf02f6e80d64a927f702dd9d631a927d87d4 upstream. This commit reverts the addition of lockdep checking to raw_seqcount_begin for the following reasons: 1) It violates the naming convention that raw_* functions should not do lockdep checks (a convention that is also followed by the other raw_*_seqcount_begin functions). 2) raw_seqcount_begin does not spin, so it can only be part of an ABBA deadlock in very special circumstances (for instance if a lock is held across the entire raw_seqcount_begin()+read_seqcount_retry() loop while also being taken inside the write_seqcount protected area). 3) It is causing false positives with some existing callers, and there is no non-lockdep alternative for those callers to use. None of the three existing callers (__d_lookup_rcu, netdev_get_name, and the NFS state code) appear to use the function in a manner that is ABBA deadlock prone. Fixes: 1ca7d67cf5d5: seqcount: Add lockdep functionality to seqcount/seqlock Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: John Stultz <john.stultz@linaro.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Waiman Long <Waiman.Long@hp.com> Cc: Stephen Boyd <sboyd@codeaurora.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/CAHQdGtRR6SvEhXiqWo24hoUh9AU9cL82Z8Z-d8-7u951F_d+5g@mail.gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/seqlock.h2
1 files changed, 0 insertions, 2 deletions
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 535f158977b9..8cf350325dc6 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -164,8 +164,6 @@ static inline unsigned read_seqcount_begin(const seqcount_t *s)
static inline unsigned raw_seqcount_begin(const seqcount_t *s)
{
unsigned ret = ACCESS_ONCE(s->sequence);
-
- seqcount_lockdep_reader_access(s);
smp_rmb();
return ret & ~1;
}