From aae1a5c1dd5bef672de0a2233f95b44f5da61d28 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Tue, 11 Aug 2020 10:54:08 +0200 Subject: [PATCH] Revert "Revert "seqlock: lockdep assert non-preemptibility on seqcount_t write"" This reverts commit 5e9203d837b3107b879a70c972c54f89882a1fd4. It should now be fixed up properly in Linus's tree, so revert this revert to clear up any merge issues with the "real" fix that is happening upstream. Link: https://lore.kernel.org/r/87v9hqxolz.fsf@nanos Signed-off-by: Greg Kroah-Hartman Change-Id: I57c6a5777befa560af8e89ff708a1be4eb46cb33 --- include/linux/seqlock.h | 29 +++++++++++++++++++++++------ 1 file changed, 23 insertions(+), 6 deletions(-) diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index e885702d8b82..54bc20496392 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -266,6 +266,12 @@ static inline void raw_write_seqcount_end(seqcount_t *s) kcsan_nestable_atomic_end(); } +static inline void __write_seqcount_begin_nested(seqcount_t *s, int subclass) +{ + raw_write_seqcount_begin(s); + seqcount_acquire(&s->dep_map, subclass, 0, _RET_IP_); +} + /** * write_seqcount_begin_nested() - start a seqcount_t write section with * custom lockdep nesting level @@ -276,8 +282,19 @@ static inline void raw_write_seqcount_end(seqcount_t *s) */ static inline void write_seqcount_begin_nested(seqcount_t *s, int subclass) { - raw_write_seqcount_begin(s); - seqcount_acquire(&s->dep_map, subclass, 0, _RET_IP_); + lockdep_assert_preemption_disabled(); + __write_seqcount_begin_nested(s, subclass); +} + +/* + * A write_seqcount_begin() variant w/o lockdep non-preemptibility checks. + * + * Use for internal seqlock.h code where it's known that preemption is + * already disabled. For example, seqlock_t write side functions. + */ +static inline void __write_seqcount_begin(seqcount_t *s) +{ + __write_seqcount_begin_nested(s, 0); } /** @@ -575,7 +592,7 @@ static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start) static inline void write_seqlock(seqlock_t *sl) { spin_lock(&sl->lock); - write_seqcount_begin(&sl->seqcount); + __write_seqcount_begin(&sl->seqcount); } /** @@ -601,7 +618,7 @@ static inline void write_sequnlock(seqlock_t *sl) static inline void write_seqlock_bh(seqlock_t *sl) { spin_lock_bh(&sl->lock); - write_seqcount_begin(&sl->seqcount); + __write_seqcount_begin(&sl->seqcount); } /** @@ -628,7 +645,7 @@ static inline void write_sequnlock_bh(seqlock_t *sl) static inline void write_seqlock_irq(seqlock_t *sl) { spin_lock_irq(&sl->lock); - write_seqcount_begin(&sl->seqcount); + __write_seqcount_begin(&sl->seqcount); } /** @@ -649,7 +666,7 @@ static inline unsigned long __write_seqlock_irqsave(seqlock_t *sl) unsigned long flags; spin_lock_irqsave(&sl->lock, flags); - write_seqcount_begin(&sl->seqcount); + __write_seqcount_begin(&sl->seqcount); return flags; }