MIPS re-enables interrupts on its idle routine and performs
a TIF_NEED_RESCHED check afterwards before putting the CPU to sleep.
The IRQs firing between the check and the 'wait' instruction may set the
TIF_NEED_RESCHED flag. In order to deal with this possible race, IRQs
interrupting __r4k_wait() rollback their return address to the
beginning of __r4k_wait() so that TIF_NEED_RESCHED is checked
again before going back to sleep.
However idle IRQs can also queue timers that may require a tick
reprogramming through a new generic idle loop iteration but those timers
would go unnoticed here because __r4k_wait() only checks
TIF_NEED_RESCHED. It doesn't check for pending timers.
Fix this with fast-forwarding idle IRQs return address to the end of the
idle routine instead of the beginning, so that the generic idle loop
handles both TIF_NEED_RESCHED and pending timers.
Signed-off-by: Marco Crivellari <marco.crivellari@xxxxxxxx>
---
arch/mips/kernel/genex.S | 36 ++++++++++++++++++++----------------
arch/mips/kernel/idle.c | 1 -
2 files changed, 20 insertions(+), 17 deletions(-)
diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index a572ce36a24f..a78d5132c940 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -104,18 +104,16 @@ handle_vcei:
__FINIT
- .align 5 /* 32 byte rollback region */
+ .align 5
LEAF(__r4k_wait)
.set push
.set noreorder
- /* start of rollback region */
- LONG_L t0, TI_FLAGS($28)
- nop
- andi t0, _TIF_NEED_RESCHED
- bnez t0, 1f
- nop
- nop
- nop
+ /* start of idle interrupt region */
+ MFC0 k0, CP0_STATUS
+ /* Enable Interrupt */
+ ori k0, 0x1f
+ xori k0, 0x1e
+ MTC0 k0, CP0_STATUS
#ifdef CONFIG_CPU_MICROMIPS
nop
nop
@@ -123,11 +121,17 @@ LEAF(__r4k_wait)
nop
#endif
.set MIPS_ISA_ARCH_LEVEL_RAW
+ /*
+ * If an interrupt lands here, between enabling interrupts above and
+ * going idle on the next instruction, we must *NOT* go idle since the
+ * interrupt could have set TIF_NEED_RESCHED or caused a timer to need
+ * resched. Fall through -- see rollback_handler below -- and have
+ * the idle loop take care of things.
+ */
wait
- /* end of rollback region (the region size must be power of two) */
-1:
+ /* end of idle interrupt region (the region size must be power of two) */
+SYM_INNER_LABEL(__r4k_wait_exit, SYM_L_LOCAL)
jr ra
- nop
.set pop
END(__r4k_wait)
@@ -136,10 +140,10 @@ LEAF(__r4k_wait)
.set push
.set noat
MFC0 k0, CP0_EPC
- PTR_LA k1, __r4k_wait
- ori k0, 0x1f /* 32 byte rollback region */
- xori k0, 0x1f
- bne k0, k1, \handler
+ PTR_LA k1, __r4k_wait_exit
+ /* 3 instructions rollback region */
+ ori k0, k0, 0x0c
+ bne k0, k1, \handler
MTC0 k0, CP0_EPC
.set pop
.endm
diff --git a/arch/mips/kernel/idle.c b/arch/mips/kernel/idle.c
index 5abc8b7340f8..1f74c0589f7e 100644
--- a/arch/mips/kernel/idle.c
+++ b/arch/mips/kernel/idle.c
@@ -37,7 +37,6 @@ static void __cpuidle r3081_wait(void)
void __cpuidle r4k_wait(void)
{
- raw_local_irq_enable();
__r4k_wait();
raw_local_irq_disable();
}
--
2.48.1
