hrtimer: Use sequence counter with associated raw spinlock (af5a06b5) · Commits · 戴 / test

A sequence counter write side critical section must be protected by some form of locking to serialize writers. A plain seqcount_t does not contain the information of which lock must be held when entering a write side critical section. Use the new seqcount_raw_spinlock_t data type, which allows to associate a raw spinlock with the sequence counter. This enables lockdep to verify that the raw spinlock used for writer serialization is held when the write side critical section is entered. If lockdep is disabled this lock association is compiled out and has neither storage size nor runtime overhead. Signed-off-by:

Ahmed S. Darwish <a.darwish@linutronix.de> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200720155530.1173732-25-a.darwish@linutronix.de

include/linux/hrtimer.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -159,7 +159,7 @@ struct hrtimer_clock_base {
		struct hrtimer_cpu_base *cpu_base;
		unsigned int index;
		clockid_t clockid;
		seqcount_t seq;
		seqcount_raw_spinlock_t seq;
		struct hrtimer *running;
		struct timerqueue_head active;
		ktime_t (*get_time)(void);

kernel/time/hrtimer.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -135,7 +135,11 @@ static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
		* timer->base->cpu_base
		*/
		static struct hrtimer_cpu_base migration_cpu_base = {
		.clock_base = { { .cpu_base = &migration_cpu_base, }, },
		.clock_base = { {
		.cpu_base = &migration_cpu_base,
		.seq = SEQCNT_RAW_SPINLOCK_ZERO(migration_cpu_base.seq,
		&migration_cpu_base.lock),
		}, },
		};

		#define migration_base migration_cpu_base.clock_base[0]
		@@ -1998,8 +2002,11 @@ int hrtimers_prepare_cpu(unsigned int cpu)
		int i;

		for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
		cpu_base->clock_base[i].cpu_base = cpu_base;
		timerqueue_init_head(&cpu_base->clock_base[i].active);
		struct hrtimer_clock_base *clock_b = &cpu_base->clock_base[i];

		clock_b->cpu_base = cpu_base;
		seqcount_raw_spinlock_init(&clock_b->seq, &cpu_base->lock);
		timerqueue_init_head(&clock_b->active);
		}

		cpu_base->cpu = cpu;

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