hrtimer: Use sequence counter with associated raw spinlock

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.

Ahmed S. Darwish committed 6 years ago

Commit af5a06b1 parent 5c73b9a2 files · +11 −4Browse files

Unified · Split

2 files

include/linux/hrtimer.h +1 −1
kernel/time/hrtimer.c +10 −3

include/linux/hrtimer.h+1−1

@@ -159,7 +159,7 @@ struct hrtimer_clock_base { · 158 unmodified lines
159	159	struct hrtimer_cpu_base *cpu_base;
160	160	unsigned int index;
161	161	clockid_t clockid;
162		− seqcount_t seq;
	162	+ seqcount_raw_spinlock_t seq;
163	163	struct hrtimer *running;
164	164	struct timerqueue_head active;
165	165	ktime_t (*get_time)(void);

kernel/time/hrtimer.c+10−3

@@ -135,7 +135,11 @@ static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = { · 134 unmodified lines
135	135	* timer->base->cpu_base
136	136	*/
137	137	static struct hrtimer_cpu_base migration_cpu_base = {
138		− .clock_base = { { .cpu_base = &migration_cpu_base, }, },
	138	+ .clock_base = { {
	139	+ .cpu_base = &migration_cpu_base,
	140	+ .seq = SEQCNT_RAW_SPINLOCK_ZERO(migration_cpu_base.seq,
	141	+ &migration_cpu_base.lock),
	142	+ }, },
139	143	};
140	144
141	145	#define migration_base migration_cpu_base.clock_base[0]
@@ -1998,8 +2002,11 @@ int hrtimers_prepare_cpu(unsigned int cpu) · 1856 unmodified lines
1998	2002	int i;
1999	2003
2000	2004	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
2001		− cpu_base->clock_base[i].cpu_base = cpu_base;
2002		− timerqueue_init_head(&cpu_base->clock_base[i].active);
	2005	+ struct hrtimer_clock_base *clock_b = &cpu_base->clock_base[i];
	2006	+
	2007	+ clock_b->cpu_base = cpu_base;
	2008	+ seqcount_raw_spinlock_init(&clock_b->seq, &cpu_base->lock);
	2009	+ timerqueue_init_head(&clock_b->active);
2003	2010	}
2004	2011
2005	2012	cpu_base->cpu = cpu;

hrtimer: Use sequence counter with associated raw spinlock

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