This is a note to let you know that I've just added the patch titled
powerpc/32bit:Store temporary result in r0 instead of r8
to the 3.9-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:
powerpc-32bit-store-temporary-result-in-r0-instead-of-r8.patch
and it can be found in the queue-3.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f7b3367774f92a688d39ed767f0ae9b93af7873a Mon Sep 17 00:00:00 2001
From: Priyanka Jain <Priyanka.Jain@xxxxxxxxxxxxx>
Date: Fri, 31 May 2013 01:20:02 +0000
Subject: powerpc/32bit:Store temporary result in r0 instead of r8
From: Priyanka Jain <Priyanka.Jain@xxxxxxxxxxxxx>
commit f7b3367774f92a688d39ed767f0ae9b93af7873a upstream.
Commit a9c4e541ea9b22944da356f2a9258b4eddcc953b
"powerpc/kprobe: Complete kprobe and migrate exception frame"
introduced a regression:
While returning from exception handling in case of PREEMPT enabled,
_TIF_NEED_RESCHED bit is checked in TI_FLAGS (thread_info flag) of current
task. Only if this bit is set, it should continue with the process of
calling preempt_schedule_irq() to schedule highest priority task if
available.
Current code assumes that r8 contains TI_FLAGS and check this for
_TIF_NEED_RESCHED, but as r8 is modified in the code which executes before
this check, r8 no longer contains the expected TI_FLAGS information.
As a result check for comparison with _TIF_NEED_RESCHED was failing even if
NEED_RESCHED bit is set in the current thread_info flag. Due to this,
preempt_schedule_irq() and in turn scheduler was not getting called even if
highest priority task is ready for execution.
So, store temporary results in r0 instead of r8 to prevent r8 from getting
modified as subsequent code is dependent on its value.
Signed-off-by: Priyanka Jain <Priyanka.Jain@xxxxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/entry_32.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -851,7 +851,7 @@ resume_kernel:
/* check current_thread_info, _TIF_EMULATE_STACK_STORE */
CURRENT_THREAD_INFO(r9, r1)
lwz r8,TI_FLAGS(r9)
- andis. r8,r8,_TIF_EMULATE_STACK_STORE@h
+ andis. r0,r8,_TIF_EMULATE_STACK_STORE@h
beq+ 1f
addi r8,r1,INT_FRAME_SIZE /* Get the kprobed function entry */
Patches currently in stable-queue which might be from Priyanka.Jain@xxxxxxxxxxxxx are
queue-3.9/powerpc-32bit-store-temporary-result-in-r0-instead-of-r8.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html