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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.

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
5.9.x+fslc
Ahmed S. Darwish 2020-07-20 17:55:30 +02:00 committed by Peter Zijlstra
parent 5c73b9a2b1
commit af5a06b582
2 changed files with 11 additions and 4 deletions
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2
include/linux/hrtimer.h
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@ -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);

13
kernel/time/hrtimer.c
View File

@ -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;