From c207a76bf155cb5cf24cf849c08f6555e9180594 Mon Sep 17 00:00:00 2001 From: John David Anglin Date: Tue, 7 May 2013 00:07:25 +0000 Subject: [PATCH] parisc: only re-enable interrupts if we need to schedule or deliver signals when returning to userspace 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 Signed-off-by: Helge Deller --- arch/parisc/kernel/entry.S | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index 36f4f1dcb778..3f3326d876f7 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -833,11 +833,6 @@ 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 */ @@ -864,6 +859,11 @@ 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 */ @@ -915,6 +915,10 @@ 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 -- 2.20.1