| Message ID | 20200630054452.3675847-17-a.darwish@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | seqlock: Extend seqcount API with associated locks | expand |
On Tue, Jun 30, 2020 at 07:44:48AM +0200, Ahmed S. Darwish wrote: > 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_spinlock_t data type, which allows to associate a > spinlock with the sequence counter. This enables lockdep to verify that > the 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> Reviewed-by: Daniel Wagner <dwagner@suse.de>
diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 8ac4aad66ebc..8e940c27c27c 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -406,7 +406,7 @@ struct ioc { enum ioc_running running; atomic64_t vtime_rate; - seqcount_t period_seqcount; + seqcount_spinlock_t period_seqcount; u32 period_at; /* wallclock starttime */ u64 period_at_vtime; /* vtime starttime */ @@ -873,7 +873,6 @@ static void ioc_now(struct ioc *ioc, struct ioc_now *now) static void ioc_start_period(struct ioc *ioc, struct ioc_now *now) { - lockdep_assert_held(&ioc->lock); WARN_ON_ONCE(ioc->running != IOC_RUNNING); write_seqcount_begin(&ioc->period_seqcount); @@ -2001,7 +2000,7 @@ static int blk_iocost_init(struct request_queue *q) ioc->running = IOC_IDLE; atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC); - seqcount_init(&ioc->period_seqcount); + seqcount_spinlock_init(&ioc->period_seqcount, &ioc->lock); ioc->period_at = ktime_to_us(ktime_get()); atomic64_set(&ioc->cur_period, 0); atomic_set(&ioc->hweight_gen, 0);
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_spinlock_t data type, which allows to associate a spinlock with the sequence counter. This enables lockdep to verify that the 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> --- block/blk-iocost.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)