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authorPriyanka Jain <Priyanka.Jain@freescale.com>2013-05-31 01:20:02 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2013-06-01 08:29:27 +1000
commitf7b3367774f92a688d39ed767f0ae9b93af7873a (patch)
treebb56b252d76d7476612ede66b15e7fea5daa0dff
parent0608d692463598c1d6e826d9dd7283381b4f246c (diff)
downloadlinux-f7b3367774f92a688d39ed767f0ae9b93af7873a.tar.gz
powerpc/32bit:Store temporary result in r0 instead of r8
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@freescale.com> CC: <stable@vger.kernel.org> [v3.7+] Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
-rw-r--r--arch/powerpc/kernel/entry_32.S2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index d22e73e4618..22b45a4955c 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -849,7 +849,7 @@ 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 */