diff options
| -rw-r--r-- | include/linux/seqlock.h | 40 |
1 files changed, 38 insertions, 2 deletions
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index bcf4cf26b8c8..61232bc223fd 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -37,9 +37,25 @@ #include <linux/preempt.h> #include <linux/lockdep.h> #include <linux/compiler.h> +#include <linux/kcsan.h> #include <asm/processor.h> /* + * The seqlock interface does not prescribe a precise sequence of read + * begin/retry/end. For readers, typically there is a call to + * read_seqcount_begin() and read_seqcount_retry(), however, there are more + * esoteric cases which do not follow this pattern. + * + * As a consequence, we take the following best-effort approach for raw usage + * via seqcount_t under KCSAN: upon beginning a seq-reader critical section, + * pessimistically mark then next KCSAN_SEQLOCK_REGION_MAX memory accesses as + * atomics; if there is a matching read_seqcount_retry() call, no following + * memory operations are considered atomic. Usage of seqlocks via seqlock_t + * interface is not affected. + */ +#define KCSAN_SEQLOCK_REGION_MAX 1000 + +/* * Version using sequence counter only. * This can be used when code has its own mutex protecting the * updating starting before the write_seqcountbeqin() and ending @@ -115,6 +131,7 @@ repeat: cpu_relax(); goto repeat; } + kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX); return ret; } @@ -131,6 +148,7 @@ static inline unsigned raw_read_seqcount(const seqcount_t *s) { unsigned ret = READ_ONCE(s->sequence); smp_rmb(); + kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX); return ret; } @@ -183,6 +201,7 @@ static inline unsigned raw_seqcount_begin(const seqcount_t *s) { unsigned ret = READ_ONCE(s->sequence); smp_rmb(); + kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX); return ret & ~1; } @@ -202,7 +221,8 @@ static inline unsigned raw_seqcount_begin(const seqcount_t *s) */ static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start) { - return unlikely(s->sequence != start); + kcsan_atomic_next(0); + return unlikely(READ_ONCE(s->sequence) != start); } /** @@ -225,6 +245,7 @@ static inline int read_seqcount_retry(const seqcount_t *s, unsigned start) static inline void raw_write_seqcount_begin(seqcount_t *s) { + kcsan_nestable_atomic_begin(); s->sequence++; smp_wmb(); } @@ -233,6 +254,7 @@ static inline void raw_write_seqcount_end(seqcount_t *s) { smp_wmb(); s->sequence++; + kcsan_nestable_atomic_end(); } /** @@ -271,9 +293,11 @@ static inline void raw_write_seqcount_end(seqcount_t *s) */ static inline void raw_write_seqcount_barrier(seqcount_t *s) { + kcsan_nestable_atomic_begin(); s->sequence++; smp_wmb(); s->sequence++; + kcsan_nestable_atomic_end(); } static inline int raw_read_seqcount_latch(seqcount_t *s) @@ -398,7 +422,9 @@ static inline void write_seqcount_end(seqcount_t *s) static inline void write_seqcount_invalidate(seqcount_t *s) { smp_wmb(); + kcsan_nestable_atomic_begin(); s->sequence+=2; + kcsan_nestable_atomic_end(); } typedef struct { @@ -430,11 +456,21 @@ typedef struct { */ static inline unsigned read_seqbegin(const seqlock_t *sl) { - return read_seqcount_begin(&sl->seqcount); + unsigned ret = read_seqcount_begin(&sl->seqcount); + + kcsan_atomic_next(0); /* non-raw usage, assume closing read_seqretry */ + kcsan_flat_atomic_begin(); + return ret; } static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start) { + /* + * Assume not nested: read_seqretry may be called multiple times when + * completing read critical section. + */ + kcsan_flat_atomic_end(); + return read_seqcount_retry(&sl->seqcount, start); } |