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seqlock: seqcount latch APIs: Only allow seqcount_latch_t 

All latch sequence counter call-sites have now been converted from plain
seqcount_t to the new seqcount_latch_t data type.

Enforce type-safety by modifying seqlock.h latch APIs to only accept
seqcount_latch_t.

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/20200827114044.11173-9-a.darwish@linutronix.de
This commit is contained in:
Ahmed S. Darwish 2020-08-27 13:40:44 +02:00 committed by Peter Zijlstra
parent 24bf401ceb
commit 0c9794c8b6
1 changed files with 15 additions and 21 deletions
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36
include/linux/seqlock.h
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@ -620,7 +620,7 @@ static inline void seqcount_latch_init(seqcount_latch_t *s)
/**
* raw_read_seqcount_latch() - pick even/odd latch data copy
* @s: Pointer to seqcount_t, seqcount_raw_spinlock_t, or seqcount_latch_t
* @s: Pointer to seqcount_latch_t
*
* See raw_write_seqcount_latch() for details and a full reader/writer
* usage example.
@ -629,17 +629,14 @@ static inline void seqcount_latch_init(seqcount_latch_t *s)
* picking which data copy to read. The full counter must then be checked
* with read_seqcount_latch_retry().
*/
#define raw_read_seqcount_latch(s) \
({ \
/* \
* Pairs with the first smp_wmb() in raw_write_seqcount_latch(). \
* Due to the dependent load, a full smp_rmb() is not needed. \
*/ \
_Generic(*(s), \
seqcount_t: READ_ONCE(((seqcount_t *)s)->sequence), \
seqcount_raw_spinlock_t: READ_ONCE(((seqcount_raw_spinlock_t *)s)->seqcount.sequence), \
seqcount_latch_t: READ_ONCE(((seqcount_latch_t *)s)->seqcount.sequence)); \
})
static inline unsigned raw_read_seqcount_latch(const seqcount_latch_t *s)
{
/*
* Pairs with the first smp_wmb() in raw_write_seqcount_latch().
* Due to the dependent load, a full smp_rmb() is not needed.
*/
return READ_ONCE(s->seqcount.sequence);
}
/**
* read_seqcount_latch_retry() - end a seqcount_latch_t read section
@ -656,7 +653,7 @@ read_seqcount_latch_retry(const seqcount_latch_t *s, unsigned start)
/**
* raw_write_seqcount_latch() - redirect latch readers to even/odd copy
* @s: Pointer to seqcount_t, seqcount_raw_spinlock_t, or seqcount_latch_t
* @s: Pointer to seqcount_latch_t
*
* The latch technique is a multiversion concurrency control method that allows
* queries during non-atomic modifications. If you can guarantee queries never
@ -735,14 +732,11 @@ read_seqcount_latch_retry(const seqcount_latch_t *s, unsigned start)
* When data is a dynamic data structure; one should use regular RCU
* patterns to manage the lifetimes of the objects within.
*/
#define raw_write_seqcount_latch(s) \
{ \
smp_wmb(); /* prior stores before incrementing "sequence" */ \
_Generic(*(s), \
seqcount_t: ((seqcount_t *)s)->sequence++, \
seqcount_raw_spinlock_t:((seqcount_raw_spinlock_t *)s)->seqcount.sequence++, \
seqcount_latch_t: ((seqcount_latch_t *)s)->seqcount.sequence++); \
smp_wmb(); /* increment "sequence" before following stores */ \
static inline void raw_write_seqcount_latch(seqcount_latch_t *s)
{
smp_wmb(); /* prior stores before incrementing "sequence" */
s->seqcount.sequence++;
smp_wmb(); /* increment "sequence" before following stores */
}
/*