From: Paul E. McKenney Date: Fri, 13 Apr 2012 03:35:13 +0000 (+0000) Subject: sparc64: Eliminate obsolete __handle_softirq() function X-Git-Tag: v3.4-rc3~15^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3d3eeb2ef26112a200785e5fca58ec58dd33bf1e;p=pandora-kernel.git sparc64: Eliminate obsolete __handle_softirq() function The invocation of softirq is now handled by irq_exit(), so there is no need for sparc64 to invoke it on the trap-return path. In fact, doing so is a bug because if the trap occurred in the idle loop, this invocation can result in lockdep-RCU failures. The problem is that RCU ignores idle CPUs, and the sparc64 trap-return path to the softirq handlers fails to tell RCU that the CPU must be considered non-idle while those handlers are executing. This means that RCU is ignoring any RCU read-side critical sections in those handlers, which in turn means that RCU-protected data can be yanked out from under those read-side critical sections. The shiny new lockdep-RCU ability to detect RCU read-side critical sections that RCU is ignoring located this problem. The fix is straightforward: Make sparc64 stop manually invoking the softirq handlers. Reported-by: Meelis Roos Suggested-by: David Miller Signed-off-by: Paul E. McKenney Tested-by: Meelis Roos Cc: stable@vger.kernel.org Signed-off-by: David S. Miller --- Reading git-diff-tree failed