diff options
Diffstat (limited to 'sys/kern/subr_smr.c')
| -rw-r--r-- | sys/kern/subr_smr.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/sys/kern/subr_smr.c b/sys/kern/subr_smr.c index c6a8f0e89015..c344fdcb7f5f 100644 --- a/sys/kern/subr_smr.c +++ b/sys/kern/subr_smr.c @@ -195,7 +195,7 @@ smr_advance(smr_t smr) * odd and an observed value of 0 in a particular CPU means * it is not currently in a read section. */ - s = smr->c_shared; + s = zpcpu_get(smr)->c_shared; goal = atomic_fetchadd_int(&s->s_wr_seq, SMR_SEQ_INCR) + SMR_SEQ_INCR; /* @@ -242,14 +242,19 @@ smr_poll(smr_t smr, smr_seq_t goal, bool wait) */ success = true; critical_enter(); - s = smr->c_shared; + s = zpcpu_get(smr)->c_shared; /* * Acquire barrier loads s_wr_seq after s_rd_seq so that we can not * observe an updated read sequence that is larger than write. */ s_rd_seq = atomic_load_acq_int(&s->s_rd_seq); - s_wr_seq = smr_current(smr); + + /* + * wr_seq must be loaded prior to any c_seq value so that a stale + * c_seq can only reference time after this wr_seq. + */ + s_wr_seq = atomic_load_acq_int(&s->s_wr_seq); /* * Detect whether the goal is valid and has already been observed. @@ -336,6 +341,12 @@ smr_poll(smr_t smr, smr_seq_t goal, bool wait) out: critical_exit(); + /* + * Serialize with smr_advance()/smr_exit(). The caller is now free + * to modify memory as expected. + */ + atomic_thread_fence_acq(); + return (success); } |