diff options
Diffstat (limited to 'debian/patches-rt/hrtimer-Introduce-expiry-spin-lock.patch')
| -rw-r--r-- | debian/patches-rt/hrtimer-Introduce-expiry-spin-lock.patch | 103 |
1 files changed, 0 insertions, 103 deletions
diff --git a/debian/patches-rt/hrtimer-Introduce-expiry-spin-lock.patch b/debian/patches-rt/hrtimer-Introduce-expiry-spin-lock.patch deleted file mode 100644 index f33cfe918..000000000 --- a/debian/patches-rt/hrtimer-Introduce-expiry-spin-lock.patch +++ /dev/null @@ -1,103 +0,0 @@ -From: Anna-Maria Gleixner <anna-maria@linutronix.de> -Date: Mon, 27 May 2019 16:54:04 +0200 -Subject: [PATCH] hrtimer: Introduce expiry spin lock -Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.17-rt9.tar.xz - -When deleting a hrtimer, it is possible, that the CPU has to spin, because the -hrtimer is marked as running. This is done via cpu_relax() and repeating trying to -delete the timer. When doing this in a virtual machine, the CPU wastes vcpu time -because of spinning as long as the timer is no longer running. - -The spinning and time wasting, could be prevented by using PARAVIRT_SPINLOCKS -and introducing a per timer base spin lock for expiry. The lock is hold during -expiring the timers of a base. When the deletion of a timer wasn't successful, -because the timer is running at the moment, the expiry lock is trying to -accessed instead of cpu_realax(). The lock is already held by the CPU expring -the timers, so the CPU could be scheduled out instead of spinning until the lock -is released, because of the PARAVIRT_SPINLOCKS code. Thereby wasting time -spinning around is prevented. - -The code isn't done conditionally on PARAVIRT_SPINLOCKS. The lock is taken only -at two places. In one of them the lock is directly dropped after accessing -it. So the probability for a slowpath when taking the lock is very low. But this -keeps the code cleaner than introducing several CONFIG_PARAVIRT_SPINLOCKS -dependend code paths and struct members. - -Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de> -Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> ---- - include/linux/hrtimer.h | 3 +++ - kernel/time/hrtimer.c | 15 ++++++++++++++- - 2 files changed, 17 insertions(+), 1 deletion(-) - ---- a/include/linux/hrtimer.h -+++ b/include/linux/hrtimer.h -@@ -183,6 +183,8 @@ enum hrtimer_base_type { - * @nr_retries: Total number of hrtimer interrupt retries - * @nr_hangs: Total number of hrtimer interrupt hangs - * @max_hang_time: Maximum time spent in hrtimer_interrupt -+ * @softirq_expiry_lock: Lock which is taken while softirq based hrtimer are -+ * expired - * @expires_next: absolute time of the next event, is required for remote - * hrtimer enqueue; it is the total first expiry time (hard - * and soft hrtimer are taken into account) -@@ -210,6 +212,7 @@ struct hrtimer_cpu_base { - unsigned short nr_hangs; - unsigned int max_hang_time; - #endif -+ spinlock_t softirq_expiry_lock; - ktime_t expires_next; - struct hrtimer *next_timer; - ktime_t softirq_expires_next; ---- a/kernel/time/hrtimer.c -+++ b/kernel/time/hrtimer.c -@@ -930,6 +930,16 @@ u64 hrtimer_forward(struct hrtimer *time - } - EXPORT_SYMBOL_GPL(hrtimer_forward); - -+static void hrtimer_grab_expiry_lock(const struct hrtimer *timer) -+{ -+ struct hrtimer_clock_base *base = timer->base; -+ -+ if (base && base->cpu_base) { -+ spin_lock(&base->cpu_base->softirq_expiry_lock); -+ spin_unlock(&base->cpu_base->softirq_expiry_lock); -+ } -+} -+ - /* - * enqueue_hrtimer - internal function to (re)start a timer - * -@@ -1162,7 +1172,7 @@ int hrtimer_cancel(struct hrtimer *timer - - if (ret >= 0) - return ret; -- cpu_relax(); -+ hrtimer_grab_expiry_lock(timer); - } - } - EXPORT_SYMBOL_GPL(hrtimer_cancel); -@@ -1459,6 +1469,7 @@ static __latent_entropy void hrtimer_run - unsigned long flags; - ktime_t now; - -+ spin_lock(&cpu_base->softirq_expiry_lock); - raw_spin_lock_irqsave(&cpu_base->lock, flags); - - now = hrtimer_update_base(cpu_base); -@@ -1468,6 +1479,7 @@ static __latent_entropy void hrtimer_run - hrtimer_update_softirq_timer(cpu_base, true); - - raw_spin_unlock_irqrestore(&cpu_base->lock, flags); -+ spin_unlock(&cpu_base->softirq_expiry_lock); - } - - #ifdef CONFIG_HIGH_RES_TIMERS -@@ -1809,6 +1821,7 @@ int hrtimers_prepare_cpu(unsigned int cp - cpu_base->softirq_next_timer = NULL; - cpu_base->expires_next = KTIME_MAX; - cpu_base->softirq_expires_next = KTIME_MAX; -+ spin_lock_init(&cpu_base->softirq_expiry_lock); - return 0; - } - |