Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 04/10] loongson: Fix idle VS timer enqueue | Date | Fri, 11 Aug 2023 19:00:43 +0200 |
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From: Peter Zijlstra <peterz@infradead.org>
Loongson 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 idling instruction may set the TIF_NEED_RESCHED flag. In order to deal with the 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 value 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.
Fixes: 0603839b18f4 (LoongArch: Add exception/interrupt handling) Tested-by: Bibo, Mao <maobibo@loongson.cn> Not-yet-signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: WANG Xuerui <kernel@xen0n.name> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> --- arch/loongarch/kernel/genex.S | 32 ++++++++++++++++++-------------- arch/loongarch/kernel/idle.c | 1 - 2 files changed, 18 insertions(+), 15 deletions(-)
diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S index 78f066384657..359d693f112e 100644 --- a/arch/loongarch/kernel/genex.S +++ b/arch/loongarch/kernel/genex.S @@ -18,27 +18,31 @@ .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 */ + move t0, CSR_CRMD_IE + 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 */ -1: jr ra + nop + /* end of idle interrupt region */ +SYM_INNER_LABEL(__arch_cpu_idle_exit, SYM_L_LOCAL) + jr ra SYM_FUNC_END(__arch_cpu_idle) SYM_FUNC_START(handle_vint) BACKUP_T0T1 SAVE_ALL - la_abs t1, __arch_cpu_idle + la_abs t1, __arch_cpu_idle_exit LONG_L t0, sp, PT_ERA - /* 32 byte rollback region */ - ori t0, t0, 0x1f - xori t0, t0, 0x1f + /* 16 byte idle interrupt region */ + ori t0, t0, 0x0f + addi.d t0, t0, 1 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 0b5dd2faeb90..5ba72d229920 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 */ raw_local_irq_disable(); } -- 2.34.1
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