3.16-stable review patch. If anyone has any objections, please let me know.
------------------ From: Trond Myklebust <[email protected]> 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 <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> Cc: John Stultz <[email protected]> Cc: "David S. Miller" <[email protected]> Cc: Al Viro <[email protected]> Cc: Waiman Long <[email protected]> Cc: Stephen Boyd <[email protected]> Cc: Linus Torvalds <[email protected]> Link: http://lkml.kernel.org/r/cahqdgtrr6svehxiqwo24houh9au9cl82z8z-d8-7u951f_d...@mail.gmail.com Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- include/linux/seqlock.h | 2 -- 1 file changed, 2 deletions(-) --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -164,8 +164,6 @@ static inline unsigned read_seqcount_beg 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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
