diff options
| author | Tanner Love <tannerlove@google.com> | 2021-06-02 21:03:38 +0300 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2021-08-10 23:50:07 +0300 |
| commit | 91cc470e797828d779cd4c1efbe8519bcb358bae (patch) | |
| tree | 9f36cb2595cd78a8d9938d002800fb0bf7e9d8a6 | |
| parent | 5a6c76b5de59ed508d7cb133327a7c54e77fed97 (diff) | |
| download | linux-91cc470e797828d779cd4c1efbe8519bcb358bae.tar.xz | |
genirq: Change force_irqthreads to a static key
With CONFIG_IRQ_FORCED_THREADING=y, testing the boolean force_irqthreads
could incur a cache line miss in invoke_softirq() and other places.
Replace the test with a static key to avoid the potential cache miss.
[ tglx: Dropped the IDE part, removed the export and updated blk-mq ]
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Tanner Love <tannerlove@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210602180338.3324213-1-tannerlove.kernel@gmail.com
| -rw-r--r-- | block/blk-mq.c | 2 | ||||
| -rw-r--r-- | include/linux/interrupt.h | 8 | ||||
| -rw-r--r-- | kernel/irq/manage.c | 11 | ||||
| -rw-r--r-- | kernel/softirq.c | 2 |
4 files changed, 12 insertions, 11 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 2c4ac51e54eb..572d8ab34014 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -606,7 +606,7 @@ static inline bool blk_mq_complete_need_ipi(struct request *rq) * This is probably worse than completing the request on a different * cache domain. */ - if (force_irqthreads) + if (force_irqthreads()) return false; /* same CPU or cache domain? Complete locally */ diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index 2ed65b01c961..1f22a30c0963 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -13,6 +13,7 @@ #include <linux/hrtimer.h> #include <linux/kref.h> #include <linux/workqueue.h> +#include <linux/jump_label.h> #include <linux/atomic.h> #include <asm/ptrace.h> @@ -474,12 +475,13 @@ extern int irq_set_irqchip_state(unsigned int irq, enum irqchip_irq_state which, #ifdef CONFIG_IRQ_FORCED_THREADING # ifdef CONFIG_PREEMPT_RT -# define force_irqthreads (true) +# define force_irqthreads() (true) # else -extern bool force_irqthreads; +DECLARE_STATIC_KEY_FALSE(force_irqthreads_key); +# define force_irqthreads() (static_branch_unlikely(&force_irqthreads_key)) # endif #else -#define force_irqthreads (0) +#define force_irqthreads() (false) #endif #ifndef local_softirq_pending diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index 766468a2fc5a..34a66c4543a2 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -25,12 +25,11 @@ #include "internals.h" #if defined(CONFIG_IRQ_FORCED_THREADING) && !defined(CONFIG_PREEMPT_RT) -__read_mostly bool force_irqthreads; -EXPORT_SYMBOL_GPL(force_irqthreads); +DEFINE_STATIC_KEY_FALSE(force_irqthreads_key); static int __init setup_forced_irqthreads(char *arg) { - force_irqthreads = true; + static_branch_enable(&force_irqthreads_key); return 0; } early_param("threadirqs", setup_forced_irqthreads); @@ -1260,8 +1259,8 @@ static int irq_thread(void *data) irqreturn_t (*handler_fn)(struct irq_desc *desc, struct irqaction *action); - if (force_irqthreads && test_bit(IRQTF_FORCED_THREAD, - &action->thread_flags)) + if (force_irqthreads() && test_bit(IRQTF_FORCED_THREAD, + &action->thread_flags)) handler_fn = irq_forced_thread_fn; else handler_fn = irq_thread_fn; @@ -1322,7 +1321,7 @@ EXPORT_SYMBOL_GPL(irq_wake_thread); static int irq_setup_forced_threading(struct irqaction *new) { - if (!force_irqthreads) + if (!force_irqthreads()) return 0; if (new->flags & (IRQF_NO_THREAD | IRQF_PERCPU | IRQF_ONESHOT)) return 0; diff --git a/kernel/softirq.c b/kernel/softirq.c index f3a012179f47..322b65d45676 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -422,7 +422,7 @@ static inline void invoke_softirq(void) if (ksoftirqd_running(local_softirq_pending())) return; - if (!force_irqthreads || !__this_cpu_read(ksoftirqd)) { + if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) { #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK /* * We can safely execute softirq on the current stack if |