From: Oleg Nesterov Date: Tue, 18 Dec 2012 00:01:38 +0000 (-0800) Subject: percpu_rw_semaphore: add lockdep annotations X-Git-Tag: v3.8-rc1~74^2~109 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8ebe34731a0d1a9d89b536430afd98d0fadec99b;p=pandora-kernel.git percpu_rw_semaphore: add lockdep annotations Add lockdep annotations. Not only this can help to find the potential problems, we do not want the false warnings if, say, the task takes two different percpu_rw_semaphore's for reading. IOW, at least ->rw_sem should not use a single class. This patch exposes this internal lock to lockdep so that it represents the whole percpu_rw_semaphore. This way we do not need to add another "fake" ->lockdep_map and lock_class_key. More importantly, this also makes the output from lockdep much more understandable if it finds the problem. In short, with this patch from lockdep pov percpu_down_read() and percpu_up_read() acquire/release ->rw_sem for reading, this matches the actual semantics. This abuses __up_read() but I hope this is fine and in fact I'd like to have down_read_no_lockdep() as well, percpu_down_read_recursive_readers() will need it. Signed-off-by: Oleg Nesterov Cc: Anton Arapov Cc: Ingo Molnar Cc: Linus Torvalds Cc: Michal Marek Cc: Mikulas Patocka Cc: "Paul E. McKenney" Cc: Peter Zijlstra Cc: Srikar Dronamraju Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed