This is a note to let you know that I've just added the patch titled
parisc: only re-enable interrupts if we need to schedule or deliver signals when returning to userspace
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:
parisc-only-re-enable-interrupts-if-we-need-to-schedule-or-deliver-signals-when-returning-to-userspace.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 c207a76bf155cb5cf24cf849c08f6555e9180594 Mon Sep 17 00:00:00 2001
From: John David Anglin <dave.anglin@xxxxxxxx>
Date: Tue, 7 May 2013 00:07:25 +0000
Subject: parisc: only re-enable interrupts if we need to schedule or deliver signals when returning to userspace
From: John David Anglin <dave.anglin@xxxxxxxx>
commit c207a76bf155cb5cf24cf849c08f6555e9180594 upstream.
Helge and I have found that we have a kernel stack overflow problem
which causes a variety of random failures.
Currently, we re-enable interrupts when returning from an external
interrupt incase we need to schedule or delivery
signals. As a result, a potentially unlimited number of interrupts
can occur while we are running on the kernel
stack. It is very limited in space (currently, 16k). This change
defers enabling interrupts until we have
actually decided to schedule or delivery signals. This only occurs
when we about to return to userspace. This
limits the number of interrupts on the kernel stack to one. In other
cases, interrupts remain disabled until the
final return from interrupt (rfi).
Signed-off-by: John David Anglin <dave.anglin@xxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/parisc/kernel/entry.S | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -825,11 +825,6 @@ ENTRY(syscall_exit_rfi)
STREG %r19,PT_SR7(%r16)
intr_return:
- /* NOTE: Need to enable interrupts incase we schedule. */
- ssm PSW_SM_I, %r0
-
-intr_check_resched:
-
/* check for reschedule */
mfctl %cr30,%r1
LDREG TI_FLAGS(%r1),%r19 /* sched.h: TIF_NEED_RESCHED */
@@ -856,6 +851,11 @@ intr_check_sig:
LDREG PT_IASQ1(%r16), %r20
cmpib,COND(=),n 0,%r20,intr_restore /* backward */
+ /* NOTE: We need to enable interrupts if we have to deliver
+ * signals. We used to do this earlier but it caused kernel
+ * stack overflows. */
+ ssm PSW_SM_I, %r0
+
copy %r0, %r25 /* long in_syscall = 0 */
#ifdef CONFIG_64BIT
ldo -16(%r30),%r29 /* Reference param save area */
@@ -907,6 +907,10 @@ intr_do_resched:
cmpib,COND(=) 0, %r20, intr_do_preempt
nop
+ /* NOTE: We need to enable interrupts if we schedule. We used
+ * to do this earlier but it caused kernel stack overflows. */
+ ssm PSW_SM_I, %r0
+
#ifdef CONFIG_64BIT
ldo -16(%r30),%r29 /* Reference param save area */
#endif
Patches currently in stable-queue which might be from dave.anglin@xxxxxxxx are
queue-3.9/parisc-only-re-enable-interrupts-if-we-need-to-schedule-or-deliver-signals-when-returning-to-userspace.patch
queue-3.9/parisc-use-long-branch-in-fork_like-macro.patch
queue-3.9/parisc-make-default-cross-compiler-search-more-robust-v3.patch
queue-3.9/parisc-fix-smp-races-when-updating-pte-and-tlb-entries-in-entry.s.patch
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