Fix a prof-related race condition.
Fix prof_lookup() to artificially raise curobjs for all paths through the code that creates a new entry in the per thread bt2cnt hash table. This fixes a race condition that could corrupt memory if prof_accum were false, and a non-default lg_prof_tcmax were used and/or threads were destroyed.
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46405e670f
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23
src/prof.c
23
src/prof.c
@ -474,11 +474,23 @@ prof_lookup(prof_bt_t *bt)
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/*
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* Artificially raise curobjs, in order to avoid a race
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* condition with prof_ctx_merge()/prof_ctx_destroy().
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*
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* No locking is necessary for ctx here because no other
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* threads have had the opportunity to fetch it from
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* bt2ctx yet.
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*/
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ctx.p->cnt_merged.curobjs++;
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new_ctx = true;
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} else
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} else {
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/*
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* Artificially raise curobjs, in order to avoid a race
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* condition with prof_ctx_merge()/prof_ctx_destroy().
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*/
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malloc_mutex_lock(&ctx.p->lock);
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ctx.p->cnt_merged.curobjs++;
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malloc_mutex_unlock(&ctx.p->lock);
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new_ctx = false;
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}
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prof_leave();
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/* Link a prof_thd_cnt_t into ctx for this thread. */
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@ -491,8 +503,9 @@ prof_lookup(prof_bt_t *bt)
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*/
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ret.p = ql_last(&prof_tdata->lru_ql, lru_link);
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assert(ret.v != NULL);
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ckh_remove(&prof_tdata->bt2cnt, ret.p->ctx->bt, NULL,
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NULL);
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if (ckh_remove(&prof_tdata->bt2cnt, ret.p->ctx->bt,
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NULL, NULL))
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assert(false);
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ql_remove(&prof_tdata->lru_ql, ret.p, lru_link);
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prof_ctx_merge(ret.p->ctx, ret.p);
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/* ret can now be re-used. */
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@ -523,7 +536,6 @@ prof_lookup(prof_bt_t *bt)
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ql_head_insert(&prof_tdata->lru_ql, ret.p, lru_link);
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malloc_mutex_lock(&ctx.p->lock);
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ql_tail_insert(&ctx.p->cnts_ql, ret.p, cnts_link);
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if (new_ctx)
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ctx.p->cnt_merged.curobjs--;
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malloc_mutex_unlock(&ctx.p->lock);
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} else {
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@ -650,7 +662,8 @@ prof_ctx_destroy(prof_ctx_t *ctx)
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assert(ctx->cnt_merged.accumobjs == 0);
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assert(ctx->cnt_merged.accumbytes == 0);
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/* Remove ctx from bt2ctx. */
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ckh_remove(&bt2ctx, ctx->bt, NULL, NULL);
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if (ckh_remove(&bt2ctx, ctx->bt, NULL, NULL))
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assert(false);
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prof_leave();
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/* Destroy ctx. */
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malloc_mutex_unlock(&ctx->lock);
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