From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20120419210820.293146495@linuxfoundation.org> Date: Thu, 19 Apr 2012 14:08:37 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Meelis Roos , David Miller , "Paul E. McKenney" Subject: [ 19/68] sparc64: Eliminate obsolete __handle_softirq() function In-Reply-To: <20120419210923.GA18589@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Paul E. McKenney" commit 3d3eeb2ef26112a200785e5fca58ec58dd33bf1e upstream. 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 Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- arch/sparc/kernel/rtrap_64.S | 7 ------- 1 file changed, 7 deletions(-) --- a/arch/sparc/kernel/rtrap_64.S +++ b/arch/sparc/kernel/rtrap_64.S @@ -20,11 +20,6 @@ .text .align 32 -__handle_softirq: - call do_softirq - nop - ba,a,pt %xcc, __handle_softirq_continue - nop __handle_preemption: call schedule wrpr %g0, RTRAP_PSTATE, %pstate @@ -89,9 +84,7 @@ rtrap: cmp %l1, 0 /* mm/ultra.S:xcall_report_regs KNOWS about this load. */ - bne,pn %icc, __handle_softirq ldx [%sp + PTREGS_OFF + PT_V9_TSTATE], %l1 -__handle_softirq_continue: rtrap_xcall: sethi %hi(0xf << 20), %l4 and %l1, %l4, %l4