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authorJohn David Anglin <dave.anglin@bell.net>2017-11-13 19:35:33 -0500
committerHelge Deller <deller@gmx.de>2017-12-17 21:06:25 +0100
commit9352aeada4d8d8753fc0e414fbfe8fdfcb68a12c (patch)
tree4465193071484ab6ca37f447812f5b488a084309 /arch/parisc
parent6a16fc322085bb3163d7d6e44856adfda06a8001 (diff)
Revert "parisc: Re-enable interrupts early"
This reverts commit 5c38602d83e584047906b41b162ababd4db4106d. Interrupts can't be enabled early because the register saves are done on the thread stack prior to switching to the IRQ stack. This caused stack overflows and the thread stack needed increasing to 32k. Even then, stack overflows still occasionally occurred. Background: Even with a 32 kB thread stack, I have seen instances where the thread stack overflowed on the mx3210 buildd. Detection of stack overflow only occurs when we have an external interrupt. When an external interrupt occurs, we switch to the thread stack if we are not already on a kernel stack. Then, registers and specials are saved to the kernel stack. The bug occurs in intr_return where interrupts are reenabled prior to returning from the interrupt. This was done incase we need to schedule or deliver signals. However, it introduces the possibility that multiple external interrupts may occur on the thread stack and cause a stack overflow. These might not be detected and cause the kernel to misbehave in random ways. This patch changes the code back to only reenable interrupts when we are going to schedule or deliver signals. As a result, we generally return from an interrupt before reenabling interrupts. This minimizes the growth of the thread stack. Fixes: 5c38602d83e5 ("parisc: Re-enable interrupts early") Signed-off-by: John David Anglin <dave.anglin@bell.net> Cc: <stable@vger.kernel.org> # v4.10+ Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to 'arch/parisc')
-rw-r--r--arch/parisc/kernel/entry.S12
1 files changed, 9 insertions, 3 deletions
diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index a4fd296c958e..f3cecf5117cf 100644
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -878,9 +878,6 @@ ENTRY_CFI(syscall_exit_rfi)
STREG %r19,PT_SR7(%r16)
intr_return:
- /* NOTE: Need to enable interrupts incase we schedule. */
- ssm PSW_SM_I, %r0
-
/* check for reschedule */
mfctl %cr30,%r1
LDREG TI_FLAGS(%r1),%r19 /* sched.h: TIF_NEED_RESCHED */
@@ -907,6 +904,11 @@ 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 */
@@ -958,6 +960,10 @@ 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