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Fix a profile sampling race.

Browse Source 
Fix a profile sampling race that was due to preparing to sample, yet
doing nothing to assure that the context remains valid until the stats
are updated.

These regressions were caused by
602c8e0971 (Implement per thread heap
profiling.), which did not make it into any releases prior to these
fixes.
This commit is contained in:
Jason Evans
2014-09-09 19:37:26 -07:00
parent 6fd53da030
commit 6e73dc194e
4 changed files with 109 additions and 73 deletions
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35
src/prof.c
View File

@@ -149,6 +149,35 @@ rb_gen(static UNUSED, tdata_tree_, prof_tdata_tree_t, prof_tdata_t, tdata_link,
/******************************************************************************/
void
prof_alloc_rollback(prof_tctx_t *tctx, bool updated)
{
prof_tdata_t *tdata;
cassert(config_prof);
if (updated) {
/*
* Compute a new sample threshold. This isn't very important in
* practice, because this function is rarely executed, so the
* potential for sample bias is minimal except in contrived
* programs.
*/
tdata = prof_tdata_get(true);
if ((uintptr_t)tdata > (uintptr_t)PROF_TDATA_STATE_MAX)
prof_sample_threshold_update(tctx->tdata);
}
if ((uintptr_t)tctx > (uintptr_t)1U) {
malloc_mutex_lock(tctx->tdata->lock);
tctx->prepared = false;
if (prof_tctx_should_destroy(tctx))
prof_tctx_destroy(tctx);
else
malloc_mutex_unlock(tctx->tdata->lock);
}
}
void
prof_malloc_sample_object(const void *ptr, size_t usize, prof_tctx_t *tctx) {
prof_tctx_set(ptr, tctx);
@@ -160,6 +189,7 @@ prof_malloc_sample_object(const void *ptr, size_t usize, prof_tctx_t *tctx) {
tctx->cnts.accumobjs++;
tctx->cnts.accumbytes += usize;
}
tctx->prepared = false;
malloc_mutex_unlock(tctx->tdata->lock);
}
@@ -529,6 +559,8 @@ prof_tctx_should_destroy(prof_tctx_t *tctx)
return (false);
if (tctx->cnts.curobjs != 0)
return (false);
if (tctx->prepared)
return (false);
return (true);
}
@@ -659,6 +691,8 @@ prof_lookup(prof_bt_t *bt)
malloc_mutex_lock(tdata->lock);
not_found = ckh_search(&tdata->bt2tctx, bt, NULL, &ret.v);
if (!not_found) /* Note double negative! */
ret.p->prepared = true;
malloc_mutex_unlock(tdata->lock);
if (not_found) {
void *btkey;
@@ -683,6 +717,7 @@ prof_lookup(prof_bt_t *bt)
ret.p->tdata = tdata;
memset(&ret.p->cnts, 0, sizeof(prof_cnt_t));
ret.p->gctx = gctx;
ret.p->prepared = true;
ret.p->state = prof_tctx_state_nominal;
malloc_mutex_lock(tdata->lock);
error = ckh_insert(&tdata->bt2tctx, btkey, ret.v);