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Inline the storage for thread name in prof_tdata_t.

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The previous approach managed the thread name in a separate buffer, which causes
races because the thread name update (triggered by new samples) can happen at
the same time as prof dumping (which reads the thread names) -- these two
operations are under separate locks to avoid blocking each other.  Implemented
the thread name storage as part of the tdata struct, which resolves the lifetime
issue and also avoids internal alloc / dalloc during prof_sample.
This commit is contained in:
Qi Wang 2023-03-28 18:02:34 -07:00 • committed by Qi Wang
parent 6cab460a45
commit ce0b7ab6c8
11 changed files with 120 additions and 103 deletions
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19
src/prof.c
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@ -415,11 +415,14 @@ prof_tdata_t *
prof_tdata_reinit(tsd_t *tsd, prof_tdata_t *tdata) {
uint64_t thr_uid = tdata->thr_uid;
uint64_t thr_discrim = tdata->thr_discrim + 1;
char *thread_name = (tdata->thread_name != NULL) ?
prof_thread_name_alloc(tsd, tdata->thread_name) : NULL;
bool active = tdata->active;
/* Keep a local copy of the thread name, before detaching. */
prof_thread_name_assert(tdata);
char thread_name[PROF_THREAD_NAME_MAX_LEN];
strncpy(thread_name, tdata->thread_name, PROF_THREAD_NAME_MAX_LEN);
prof_tdata_detach(tsd, tdata);
return prof_tdata_init_impl(tsd, thr_uid, thr_discrim, thread_name,
active);
}
@ -464,15 +467,15 @@ prof_active_set(tsdn_t *tsdn, bool active) {
const char *
prof_thread_name_get(tsd_t *tsd) {
static const char *prof_thread_name_dummy = "";
assert(tsd_reentrancy_level_get(tsd) == 0);
prof_tdata_t *tdata;
tdata = prof_tdata_get(tsd, true);
prof_tdata_t *tdata = prof_tdata_get(tsd, true);
if (tdata == NULL) {
return "";
return prof_thread_name_dummy;
}
return (tdata->thread_name != NULL ? tdata->thread_name : "");
return tdata->thread_name;
}
int