From: Oleg Nesterov Date: Wed, 27 Apr 2011 18:59:41 +0000 (+0200) Subject: signal: sigprocmask() should do retarget_shared_pending() X-Git-Tag: v3.0-rc1~382^2~12 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e6fa16ab9c1e9b344428e6fea4d29e3cc4b28fb0;p=pandora-kernel.git signal: sigprocmask() should do retarget_shared_pending() In short, almost every changing of current->blocked is wrong, or at least can lead to the unexpected results. For example. Two threads T1 and T2, T1 sleeps in sigtimedwait/pause/etc. kill(tgid, SIG) can pick T2 for TIF_SIGPENDING. If T2 calls sigprocmask() and blocks SIG before it notices the pending signal, nobody else can handle this pending shared signal. I am not sure this is bug, but at least this looks strange imho. T1 should not sleep forever, there is a signal which should wake it up. This patch moves the code which actually changes ->blocked into the new helper, set_current_blocked() and changes this code to call retarget_shared_pending() as exit_signals() does. We should only care about the signals we just blocked, we use "newset & ~current->blocked" as a mask. We do not check !sigisemptyset(newblocked), retarget_shared_pending() is cheap unless mask & shared_pending. Note: for this particular case we could simply change sigprocmask() to return -EINTR if signal_pending(), but then we should change other callers and, more importantly, if we need this fix then set_current_blocked() will have more callers and some of them can't restart. See the next patch as a random example. Signed-off-by: Oleg Nesterov Reviewed-by: Matt Fleming Acked-by: Tejun Heo --- Reading git-diff-tree failed