diff options
Diffstat (limited to 'src/support/hazard.c')
| -rw-r--r-- | src/support/hazard.c | 57 |
1 files changed, 26 insertions, 31 deletions
diff --git a/src/support/hazard.c b/src/support/hazard.c index 27508bbdece..b0fa7e129bb 100644 --- a/src/support/hazard.c +++ b/src/support/hazard.c @@ -26,7 +26,6 @@ __wt_hazard_set(WT_SESSION_IMPL *session, WT_REF *ref, bool *busyp WT_BTREE *btree; WT_CONNECTION_IMPL *conn; WT_HAZARD *hp; - WT_PAGE *page; int restarts = 0; btree = S2BT(session); @@ -38,11 +37,11 @@ __wt_hazard_set(WT_SESSION_IMPL *session, WT_REF *ref, bool *busyp return (0); /* - * If there isn't a valid page pointer, we're done. This read can race - * with eviction and splits, we re-check it after a barrier to make - * sure we have a valid pointer. + * If there isn't a valid page, we're done. This read can race with + * eviction and splits, we re-check it after a barrier to make sure + * we have a valid reference. */ - if (ref->state != WT_REF_MEM || (page = ref->page) == NULL) { + if (ref->state != WT_REF_MEM) { *busyp = true; return (0); } @@ -90,10 +89,10 @@ __wt_hazard_set(WT_SESSION_IMPL *session, WT_REF *ref, bool *busyp conn->hazard_max)); } - if (hp->page != NULL) + if (hp->ref != NULL) continue; - hp->page = page; + hp->ref = ref; #ifdef HAVE_DIAGNOSTIC hp->file = file; hp->line = line; @@ -103,21 +102,17 @@ __wt_hazard_set(WT_SESSION_IMPL *session, WT_REF *ref, bool *busyp /* * Check if the page state is still valid, where valid means a - * state of WT_REF_MEM and the pointer is unchanged. (The - * pointer can change, it means the page was evicted between - * the time we set our hazard pointer and the publication. It - * would theoretically be possible for the page to be evicted - * and a different page read into the same memory, so the - * pointer hasn't changed but the contents have. That's OK, we - * found this page using the tree's key space, whatever page we - * find here is the page for us to use.) + * state of WT_REF_MEM. */ if (ref->state == WT_REF_MEM) { + ++session->nhazard; + + /* + * Callers require a barrier here so operations holding + * the hazard pointer see consistent data. + */ WT_READ_BARRIER(); - if (ref->page == page) { - ++session->nhazard; - return (0); - } + return (0); } /* @@ -130,7 +125,7 @@ __wt_hazard_set(WT_SESSION_IMPL *session, WT_REF *ref, bool *busyp * We don't bother publishing this update: the worst case is we * prevent some random page from being evicted. */ - hp->page = NULL; + hp->ref = NULL; *busyp = true; return (0); } @@ -147,7 +142,7 @@ __wt_hazard_set(WT_SESSION_IMPL *session, WT_REF *ref, bool *busyp * Clear a hazard pointer. */ int -__wt_hazard_clear(WT_SESSION_IMPL *session, WT_PAGE *page) +__wt_hazard_clear(WT_SESSION_IMPL *session, WT_REF *ref) { WT_BTREE *btree; WT_HAZARD *hp; @@ -165,7 +160,7 @@ __wt_hazard_clear(WT_SESSION_IMPL *session, WT_PAGE *page) for (hp = session->hazard + session->hazard_size - 1; hp >= session->hazard; --hp) - if (hp->page == page) { + if (hp->ref == ref) { /* * We don't publish the hazard pointer clear in the * general case. It's not required for correctness; @@ -174,7 +169,7 @@ __wt_hazard_clear(WT_SESSION_IMPL *session, WT_PAGE *page) * generation number was just set, it's unlikely the * page will be selected for eviction. */ - hp->page = NULL; + hp->ref = NULL; /* * If this was the last hazard pointer in the session, @@ -191,7 +186,7 @@ __wt_hazard_clear(WT_SESSION_IMPL *session, WT_PAGE *page) */ WT_PANIC_RET(session, EINVAL, "session %p: clear hazard pointer: %p: not found", - (void *)session, (void *)page); + (void *)session, (void *)ref); } /* @@ -211,7 +206,7 @@ __wt_hazard_close(WT_SESSION_IMPL *session) */ for (found = false, hp = session->hazard; hp < session->hazard + session->hazard_size; ++hp) - if (hp->page != NULL) { + if (hp->ref != NULL) { found = true; break; } @@ -239,8 +234,8 @@ __wt_hazard_close(WT_SESSION_IMPL *session) */ for (hp = session->hazard; hp < session->hazard + session->hazard_size; ++hp) - if (hp->page != NULL) { - hp->page = NULL; + if (hp->ref != NULL) { + hp->ref = NULL; --session->nhazard; } @@ -256,7 +251,7 @@ __wt_hazard_close(WT_SESSION_IMPL *session) * Count how many hazard pointers this session has on the given page. */ u_int -__wt_hazard_count(WT_SESSION_IMPL *session, WT_PAGE *page) +__wt_hazard_count(WT_SESSION_IMPL *session, WT_REF *ref) { WT_HAZARD *hp; u_int count; @@ -264,7 +259,7 @@ __wt_hazard_count(WT_SESSION_IMPL *session, WT_PAGE *page) for (count = 0, hp = session->hazard + session->hazard_size - 1; hp >= session->hazard; --hp) - if (hp->page == page) + if (hp->ref == ref) ++count; return (count); @@ -282,10 +277,10 @@ __hazard_dump(WT_SESSION_IMPL *session) for (hp = session->hazard; hp < session->hazard + session->hazard_size; ++hp) - if (hp->page != NULL) + if (hp->ref != NULL) __wt_errx(session, "session %p: hazard pointer %p: %s, line %d", (void *)session, - (void *)hp->page, hp->file, hp->line); + (void *)hp->ref, hp->file, hp->line); } #endif |