Commit 8aa9e85adac609588eeec356e5a85059b3b819ba
Committed by
Linus Torvalds
1 parent
71dc96e39d
Exists in
master
and in
13 other branches
ARC: !PREEMPT: Ensure Return to kernel mode is IRQ safe
There was a very small race window where resume to kernel mode from a Exception Path (or pure kernel mode which is true for most of ARC exceptions anyways), was not disabling interrupts in restore_regs, clobbering the exception regs Anton found the culprit call flow (after many sleepless nights) | 1. we got a Trap from user land | 2. started to service it. | 3. While doing some stuff on user-land memory (I think it is padzero()), | we got a DataTlbMiss | 4. On return from it we are taking "resume_kernel_mode" path | 5. NEED_RESHED is not set, so we go to "return from exception" path in | restore regs. | 6. there seems to be IRQ happening Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Cc: <stable@vger.kernel.org> #3.10, 3.12, 3.13, 3.14 Cc: Anton Kolesov <Anton.Kolesov@synopsys.com> Cc: Francois Bedard <Francois.Bedard@synopsys.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Showing 1 changed file with 5 additions and 3 deletions Side-by-side Diff
arch/arc/kernel/entry.S
... | ... | @@ -614,10 +614,12 @@ |
614 | 614 | |
615 | 615 | resume_kernel_mode: |
616 | 616 | |
617 | -#ifdef CONFIG_PREEMPT | |
618 | - | |
619 | - ; This is a must for preempt_schedule_irq() | |
617 | + ; Disable Interrupts from this point on | |
618 | + ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq() | |
619 | + ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe | |
620 | 620 | IRQ_DISABLE r9 |
621 | + | |
622 | +#ifdef CONFIG_PREEMPT | |
621 | 623 | |
622 | 624 | ; Can't preempt if preemption disabled |
623 | 625 | GET_CURR_THR_INFO_FROM_SP r10 |