project-base/server-skynet-source-3rd-jemalloc
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Fix prof bugs.

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Fix a race condition in ctx destruction that could cause undefined
behavior (deadlock observed).

Add mutex unlocks to some OOM error paths.
This commit is contained in:
Jason Evans 2010-10-27 19:47:40 -07:00
parent d4bab21756
commit b04a940ee5
1 changed files with 29 additions and 6 deletions
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35
jemalloc/src/prof.c
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@ -255,6 +255,7 @@ prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
} else \ } else \
return; return;
assert(nignore <= 3);
assert(max <= (1U << opt_lg_prof_bt_max)); assert(max <= (1U << opt_lg_prof_bt_max));
BT_FRAME(0) BT_FRAME(0)
@ -398,7 +399,7 @@ prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
BT_FRAME(126) BT_FRAME(126)
BT_FRAME(127) BT_FRAME(127)
/* Extras to compensate for NIGNORE. */ /* Extras to compensate for nignore. */
BT_FRAME(128) BT_FRAME(128)
BT_FRAME(129) BT_FRAME(129)
BT_FRAME(130) BT_FRAME(130)
@ -496,8 +497,10 @@ prof_lookup(prof_bt_t *bt)
opt_lg_prof_tcmax)); opt_lg_prof_tcmax));
/* Allocate and partially initialize a new cnt. */ /* Allocate and partially initialize a new cnt. */
ret.v = imalloc(sizeof(prof_thr_cnt_t)); ret.v = imalloc(sizeof(prof_thr_cnt_t));
if (ret.p == NULL) if (ret.p == NULL) {
malloc_mutex_unlock(&ctx.p->lock);
return (NULL); return (NULL);
}
ql_elm_new(ret.p, cnts_link); ql_elm_new(ret.p, cnts_link);
ql_elm_new(ret.p, lru_link); ql_elm_new(ret.p, lru_link);
} }
@ -506,6 +509,7 @@ prof_lookup(prof_bt_t *bt)
ret.p->epoch = 0; ret.p->epoch = 0;
memset(&ret.p->cnts, 0, sizeof(prof_cnt_t)); memset(&ret.p->cnts, 0, sizeof(prof_cnt_t));
if (ckh_insert(&prof_tdata->bt2cnt, btkey.v, ret.v)) { if (ckh_insert(&prof_tdata->bt2cnt, btkey.v, ret.v)) {
malloc_mutex_unlock(&ctx.p->lock);
idalloc(ret.v); idalloc(ret.v);
return (NULL); return (NULL);
} }
@ -625,11 +629,14 @@ prof_ctx_destroy(prof_ctx_t *ctx)
/* /*
* Check that ctx is still unused by any thread cache before destroying * Check that ctx is still unused by any thread cache before destroying
* it. prof_lookup() interlocks bt2ctx_mtx and ctx->lock in order to * it. prof_lookup() interlocks bt2ctx_mtx and ctx->lock in order to
* avoid a race condition with this function. * avoid a race condition with this function, and prof_ctx_merge()
* artificially raises ctx->cnt_merged.curobjs in order to avoid a race
* between the main body of prof_ctx_merge() and entry into this
* function.
*/ */
prof_enter(); prof_enter();
malloc_mutex_lock(&ctx->lock); malloc_mutex_lock(&ctx->lock);
if (ql_first(&ctx->cnts_ql) == NULL && ctx->cnt_merged.curobjs == 0) { if (ql_first(&ctx->cnts_ql) == NULL && ctx->cnt_merged.curobjs == 1) {
assert(ctx->cnt_merged.curbytes == 0); assert(ctx->cnt_merged.curbytes == 0);
assert(ctx->cnt_merged.accumobjs == 0); assert(ctx->cnt_merged.accumobjs == 0);
assert(ctx->cnt_merged.accumbytes == 0); assert(ctx->cnt_merged.accumbytes == 0);
@ -642,6 +649,8 @@ prof_ctx_destroy(prof_ctx_t *ctx)
malloc_mutex_destroy(&ctx->lock); malloc_mutex_destroy(&ctx->lock);
idalloc(ctx); idalloc(ctx);
} else { } else {
/* Compensate for increment in prof_ctx_merge(). */
ctx->cnt_merged.curobjs--;
malloc_mutex_unlock(&ctx->lock); malloc_mutex_unlock(&ctx->lock);
prof_leave(); prof_leave();
} }
@ -660,9 +669,23 @@ prof_ctx_merge(prof_ctx_t *ctx, prof_thr_cnt_t *cnt)
ctx->cnt_merged.accumbytes += cnt->cnts.accumbytes; ctx->cnt_merged.accumbytes += cnt->cnts.accumbytes;
ql_remove(&ctx->cnts_ql, cnt, cnts_link); ql_remove(&ctx->cnts_ql, cnt, cnts_link);
if (opt_prof_accum == false && ql_first(&ctx->cnts_ql) == NULL && if (opt_prof_accum == false && ql_first(&ctx->cnts_ql) == NULL &&
ctx->cnt_merged.curobjs == 0) ctx->cnt_merged.curobjs == 0) {
/*
* Artificially raise ctx->cnt_merged.curobjs in order to keep
* another thread from winning the race to destroy ctx while
* this one has ctx->lock dropped. Without this, it would be
* possible for another thread to:
*
* 1) Sample an allocation associated with ctx.
* 2) Deallocate the sampled object.
* 3) Successfully prof_ctx_destroy(ctx).
*
* The result would be that ctx no longer exists by the time
* this thread accesses it in prof_ctx_destroy().
*/
ctx->cnt_merged.curobjs++;
destroy = true; destroy = true;
else } else
destroy = false; destroy = false;
malloc_mutex_unlock(&ctx->lock); malloc_mutex_unlock(&ctx->lock);
if (destroy) if (destroy)