diff options
Diffstat (limited to 'block/blk.h')
| -rw-r--r-- | block/blk.h | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/block/blk.h b/block/blk.h index b998a7761faf..17e03656ba9a 100644 --- a/block/blk.h +++ b/block/blk.h @@ -689,6 +689,7 @@ static inline int req_ref_read(struct request *req) static inline u64 blk_time_get_ns(void) { struct blk_plug *plug = current->plug; + u64 now; if (!plug || !in_task()) return ktime_get_ns(); @@ -697,12 +698,18 @@ static inline u64 blk_time_get_ns(void) * 0 could very well be a valid time, but rather than flag "this is * a valid timestamp" separately, just accept that we'll do an extra * ktime_get_ns() if we just happen to get 0 as the current time. + * + * cur_ktime can be zeroed by pre-emption the moment PF_BLOCK_TS is set. */ - if (!plug->cur_ktime) { - plug->cur_ktime = ktime_get_ns(); + now = READ_ONCE(plug->cur_ktime); + if (!now) { + now = ktime_get_ns(); + WRITE_ONCE(plug->cur_ktime, now); + /* Ensure PF_BLOCK_TS is set after cur_ktime. */ + barrier(); current->flags |= PF_BLOCK_TS; } - return plug->cur_ktime; + return now; } static inline ktime_t blk_time_get(void) |