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Fix prof regressions.

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Fix prof regressions related to tdata (main per thread profiling data
structure) destruction:
- Deadlock.  The fix for this was intended to be part of
  20c31deaae (Test prof.reset mallctl and
  fix numerous discovered bugs.) but the fix was left incomplete.
- Destruction race.  Detaching tdata just prior to destruction without
  holding the tdatas lock made it possible for another thread to destroy
  the tdata out from under the thread that was on its way to doing so.
This commit is contained in:
Jason Evans 2014-10-04 15:03:49 -07:00
parent 16854ebeb7
commit f04a0bef99
1 changed files with 23 additions and 16 deletions
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37
src/prof.c
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@ -116,8 +116,10 @@ static bool prof_booted = false;
static bool prof_tctx_should_destroy(prof_tctx_t *tctx); static bool prof_tctx_should_destroy(prof_tctx_t *tctx);
static void prof_tctx_destroy(tsd_t *tsd, prof_tctx_t *tctx); static void prof_tctx_destroy(tsd_t *tsd, prof_tctx_t *tctx);
static bool prof_tdata_should_destroy(prof_tdata_t *tdata); static bool prof_tdata_should_destroy(prof_tdata_t *tdata,
static void prof_tdata_destroy(tsd_t *tsd, prof_tdata_t *tdata); bool even_if_attached);
static void prof_tdata_destroy(tsd_t *tsd, prof_tdata_t *tdata,
bool even_if_attached);
static char *prof_thread_name_alloc(tsd_t *tsd, const char *thread_name); static char *prof_thread_name_alloc(tsd_t *tsd, const char *thread_name);
/******************************************************************************/ /******************************************************************************/
@ -616,7 +618,7 @@ prof_tctx_destroy(tsd_t *tsd, prof_tctx_t *tctx)
assert(tctx->cnts.accumbytes == 0); assert(tctx->cnts.accumbytes == 0);
ckh_remove(tsd, &tdata->bt2tctx, &gctx->bt, NULL, NULL); ckh_remove(tsd, &tdata->bt2tctx, &gctx->bt, NULL, NULL);
destroy_tdata = prof_tdata_should_destroy(tdata); destroy_tdata = prof_tdata_should_destroy(tdata, false);
malloc_mutex_unlock(tdata->lock); malloc_mutex_unlock(tdata->lock);
malloc_mutex_lock(gctx->lock); malloc_mutex_lock(gctx->lock);
@ -644,7 +646,7 @@ prof_tctx_destroy(tsd_t *tsd, prof_tctx_t *tctx)
prof_gctx_try_destroy(tsd, gctx, tdata); prof_gctx_try_destroy(tsd, gctx, tdata);
if (destroy_tdata) if (destroy_tdata)
prof_tdata_destroy(tsd, tdata); prof_tdata_destroy(tsd, tdata, false);
idalloc(tsd, tctx); idalloc(tsd, tctx);
} }
@ -1656,10 +1658,10 @@ prof_tdata_init(tsd_t *tsd)
/* tdata->lock must be held. */ /* tdata->lock must be held. */
static bool static bool
prof_tdata_should_destroy(prof_tdata_t *tdata) prof_tdata_should_destroy(prof_tdata_t *tdata, bool even_if_attached)
{ {
if (tdata->attached) if (tdata->attached && !even_if_attached)
return (false); return (false);
if (ckh_count(&tdata->bt2tctx) != 0) if (ckh_count(&tdata->bt2tctx) != 0)
return (false); return (false);
@ -1668,10 +1670,11 @@ prof_tdata_should_destroy(prof_tdata_t *tdata)
/* tdatas_mtx must be held. */ /* tdatas_mtx must be held. */
static void static void
prof_tdata_destroy_locked(tsd_t *tsd, prof_tdata_t *tdata) prof_tdata_destroy_locked(tsd_t *tsd, prof_tdata_t *tdata,
bool even_if_attached)
{ {
assert(prof_tdata_should_destroy(tdata)); assert(prof_tdata_should_destroy(tdata, even_if_attached));
assert(tsd_prof_tdata_get(tsd) != tdata); assert(tsd_prof_tdata_get(tsd) != tdata);
tdata_tree_remove(&tdatas, tdata); tdata_tree_remove(&tdatas, tdata);
@ -1683,11 +1686,11 @@ prof_tdata_destroy_locked(tsd_t *tsd, prof_tdata_t *tdata)
} }
static void static void
prof_tdata_destroy(tsd_t *tsd, prof_tdata_t *tdata) prof_tdata_destroy(tsd_t *tsd, prof_tdata_t *tdata, bool even_if_attached)
{ {
malloc_mutex_lock(&tdatas_mtx); malloc_mutex_lock(&tdatas_mtx);
prof_tdata_destroy_locked(tsd, tdata); prof_tdata_destroy_locked(tsd, tdata, even_if_attached);
malloc_mutex_unlock(&tdatas_mtx); malloc_mutex_unlock(&tdatas_mtx);
} }
@ -1698,14 +1701,19 @@ prof_tdata_detach(tsd_t *tsd, prof_tdata_t *tdata)
malloc_mutex_lock(tdata->lock); malloc_mutex_lock(tdata->lock);
if (tdata->attached) { if (tdata->attached) {
destroy_tdata = prof_tdata_should_destroy(tdata, true);
/*
* Only detach if !destroy_tdata, because detaching would allow
* another thread to win the race to destroy tdata.
*/
if (!destroy_tdata)
tdata->attached = false; tdata->attached = false;
destroy_tdata = prof_tdata_should_destroy(tdata);
tsd_prof_tdata_set(tsd, NULL); tsd_prof_tdata_set(tsd, NULL);
} else } else
destroy_tdata = false; destroy_tdata = false;
malloc_mutex_unlock(tdata->lock); malloc_mutex_unlock(tdata->lock);
if (destroy_tdata) if (destroy_tdata)
prof_tdata_destroy(tsd, tdata); prof_tdata_destroy(tsd, tdata, true);
} }
prof_tdata_t * prof_tdata_t *
@ -1731,7 +1739,7 @@ prof_tdata_expire(prof_tdata_t *tdata)
if (!tdata->expired) { if (!tdata->expired) {
tdata->expired = true; tdata->expired = true;
destroy_tdata = tdata->attached ? false : destroy_tdata = tdata->attached ? false :
prof_tdata_should_destroy(tdata); prof_tdata_should_destroy(tdata, false);
} else } else
destroy_tdata = false; destroy_tdata = false;
malloc_mutex_unlock(tdata->lock); malloc_mutex_unlock(tdata->lock);
@ -1764,8 +1772,7 @@ prof_reset(tsd_t *tsd, size_t lg_sample)
prof_tdata_reset_iter, NULL); prof_tdata_reset_iter, NULL);
if (to_destroy != NULL) { if (to_destroy != NULL) {
next = tdata_tree_next(&tdatas, to_destroy); next = tdata_tree_next(&tdatas, to_destroy);
tdata_tree_remove(&tdatas, to_destroy); prof_tdata_destroy_locked(tsd, to_destroy, false);
prof_tdata_destroy(tsd, to_destroy);
} else } else
next = NULL; next = NULL;
} while (next != NULL); } while (next != NULL);