From: Oleg Nesterov Date: Sat, 24 Nov 2012 16:29:40 +0000 (+0100) Subject: uprobes: Introduce uprobe->register_rwsem X-Git-Tag: v3.9-rc1~173^2~2^2~31 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e591c8d78e49e6206935cf31c4d2b603bbb29166;p=pandora-kernel.git uprobes: Introduce uprobe->register_rwsem Introduce uprobe->register_rwsem. It is taken for writing around __uprobe_register/unregister. Change handler_chain() to use this sem rather than consumer_rwsem. The main reason for this change is that we have the nasty problem with mmap_sem/consumer_rwsem dependency. filter_chain() needs to protect uprobe->consumers like handler_chain(), but they can not use the same lock. filter_chain() can be called under ->mmap_sem (currently this is always true), but we want to allow ->handler() to play with the probed task's memory, and this needs ->mmap_sem. Alternatively we could use srcu, but synchronize_srcu() is very slow and ->register_rwsem allows us to do more. In particular, we can teach handler_chain() to do remove_breakpoint() if this bp is "nacked" by all consumers, we know that we can't race with the new consumer which does uprobe_register(). See also the next patches. uprobes_mutex[] is almost ready to die. Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju --- Reading git-diff-tree failed