This is a note to let you know that I've just added the patch titled
sparc64: Eliminate obsolete __handle_softirq() function
to the 3.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sparc64-eliminate-obsolete-__handle_softirq-function.patch
and it can be found in the queue-3.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 3d3eeb2ef26112a200785e5fca58ec58dd33bf1e Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <[email protected]>
Date: Fri, 13 Apr 2012 03:35:13 +0000
Subject: sparc64: Eliminate obsolete __handle_softirq() function
From: "Paul E. McKenney" <[email protected]>
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 <[email protected]>
Suggested-by: David Miller <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Tested-by: Meelis Roos <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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
Patches currently in stable-queue which might be from
[email protected] are
queue-3.2/sparc64-eliminate-obsolete-__handle_softirq-function.patch
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