6.12-stable review patch. If anyone has any objections, please let me know.
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From: Marco Crivellari marco.crivellari@suse.com
[ Upstream commit edb1942542bc538707cea221e9c7923a6270465f ]
LoongArch 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 idle instruction may set the TIF_NEED_RESCHED flag. In order to deal with such a race, IRQs interrupting __arch_cpu_idle() rollback their return address to the beginning of __arch_cpu_idle() 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 __arch_cpu_idle() 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 can handle both TIF_NEED_RESCHED and pending timers.
Fixes: 0603839b18f4 ("LoongArch: Add exception/interrupt handling") Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Frederic Weisbecker frederic@kernel.org Signed-off-by: Marco Crivellari marco.crivellari@suse.com Signed-off-by: Huacai Chen chenhuacai@loongson.cn Signed-off-by: Sasha Levin sashal@kernel.org --- arch/loongarch/kernel/genex.S | 28 +++++++++++++++------------- arch/loongarch/kernel/idle.c | 3 +-- arch/loongarch/kernel/reset.c | 6 +++--- 3 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S index 86d5d90ebefe5..4f09121417818 100644 --- a/arch/loongarch/kernel/genex.S +++ b/arch/loongarch/kernel/genex.S @@ -18,16 +18,19 @@
.align 5 SYM_FUNC_START(__arch_cpu_idle) - /* start of rollback region */ - LONG_L t0, tp, TI_FLAGS - nop - andi t0, t0, _TIF_NEED_RESCHED - bnez t0, 1f - nop - nop - nop + /* start of idle interrupt region */ + ori t0, zero, CSR_CRMD_IE + /* idle instruction needs irq enabled */ + csrxchg t0, t0, LOONGARCH_CSR_CRMD + /* + * 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 an timer to need + * reprogramming. Fall through -- see handle_vint() below -- and have + * the idle loop take care of things. + */ idle 0 - /* end of rollback region */ + /* end of idle interrupt region */ 1: jr ra SYM_FUNC_END(__arch_cpu_idle)
@@ -35,11 +38,10 @@ SYM_CODE_START(handle_vint) UNWIND_HINT_UNDEFINED BACKUP_T0T1 SAVE_ALL - la_abs t1, __arch_cpu_idle + la_abs t1, 1b LONG_L t0, sp, PT_ERA - /* 32 byte rollback region */ - ori t0, t0, 0x1f - xori t0, t0, 0x1f + /* 3 instructions idle interrupt region */ + ori t0, t0, 0b1100 bne t0, t1, 1f LONG_S t0, sp, PT_ERA 1: move a0, sp diff --git a/arch/loongarch/kernel/idle.c b/arch/loongarch/kernel/idle.c index 0b5dd2faeb90b..54b247d8cdb69 100644 --- a/arch/loongarch/kernel/idle.c +++ b/arch/loongarch/kernel/idle.c @@ -11,7 +11,6 @@
void __cpuidle arch_cpu_idle(void) { - raw_local_irq_enable(); - __arch_cpu_idle(); /* idle instruction needs irq enabled */ + __arch_cpu_idle(); raw_local_irq_disable(); } diff --git a/arch/loongarch/kernel/reset.c b/arch/loongarch/kernel/reset.c index 1ef8c63835351..de8fa5a8a825c 100644 --- a/arch/loongarch/kernel/reset.c +++ b/arch/loongarch/kernel/reset.c @@ -33,7 +33,7 @@ void machine_halt(void) console_flush_on_panic(CONSOLE_FLUSH_PENDING);
while (true) { - __arch_cpu_idle(); + __asm__ __volatile__("idle 0" : : : "memory"); } }
@@ -53,7 +53,7 @@ void machine_power_off(void) #endif
while (true) { - __arch_cpu_idle(); + __asm__ __volatile__("idle 0" : : : "memory"); } }
@@ -74,6 +74,6 @@ void machine_restart(char *command) acpi_reboot();
while (true) { - __arch_cpu_idle(); + __asm__ __volatile__("idle 0" : : : "memory"); } }