BUG/MAJOR: threads/freq_ctr: fix lock on freq counters.
The wrong bit was set to keep the lock on freq counter update. And the read functions were re-worked to use volatile. Moreover, when a freq counter is updated, it is now rotated only if the current counter is in the past (now.tv_sec > ctr->curr_sec). It is important with threads because the current time (now) is thread-local. So, rounded to the second, the time may vary by more or less 1 second. So a freq counter rotated by one thread may be see 1 second in the future. In this case, it is updated but not rotated.
This commit is contained in:
Emeric Brun
Willy Tarreau
parent
a1ae7e81cd
commit
6e0128630b
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@ -34,7 +34,7 @@
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*/
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static inline unsigned int update_freq_ctr(struct freq_ctr *ctr, unsigned int inc)
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{
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unsigned int elapsed;
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int elapsed;
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unsigned int tot_inc;
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unsigned int curr_sec;
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@ -42,23 +42,24 @@ static inline unsigned int update_freq_ctr(struct freq_ctr *ctr, unsigned int in
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/* remove the bit, used for the lock */
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curr_sec = ctr->curr_sec & 0x7fffffff;
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}
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while (!HA_ATOMIC_CAS(&ctr->curr_sec, &curr_sec, curr_sec | 0x8000000));
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while (!HA_ATOMIC_CAS(&ctr->curr_sec, &curr_sec, curr_sec | 0x80000000));
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elapsed = (now.tv_sec & 0x7fffffff)- curr_sec;
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if (unlikely(elapsed)) {
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if (unlikely(elapsed > 0)) {
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ctr->prev_ctr = ctr->curr_ctr;
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ctr->curr_ctr = 0;
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if (likely(elapsed != 1)) {
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/* we missed more than one second */
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ctr->prev_ctr = 0;
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}
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curr_sec = now.tv_sec;
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}
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ctr->curr_ctr += inc;
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tot_inc = ctr->curr_ctr;
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/* release the lock and update the time in case of rotate. */
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HA_ATOMIC_STORE(&ctr->curr_sec, now.tv_sec & 0x7fffffff);
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HA_ATOMIC_STORE(&ctr->curr_sec, curr_sec & 0x7fffffff);
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return tot_inc;
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/* Note: later we may want to propagate the update to other counters */
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}
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113
src/freq_ctr.c
113
src/freq_ctr.c
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@ -30,18 +30,21 @@
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*/
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unsigned int read_freq_ctr(struct freq_ctr *ctr)
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{
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unsigned int curr, past;
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unsigned int age, curr_sec;
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unsigned int curr, past, _curr, _past;
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unsigned int age, curr_sec, _curr_sec;
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do {
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curr = ctr->curr_ctr;
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past = ctr->prev_ctr;
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curr_sec = ctr->curr_sec;
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} while (curr != ctr->curr_ctr
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|| past != ctr->prev_ctr
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|| curr_sec != ctr->curr_sec
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|| (curr_sec & 0x80000000));
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while(1) {
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_curr = (volatile unsigned int)ctr->curr_ctr;
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_past = (volatile unsigned int)ctr->prev_ctr;
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_curr_sec = (volatile unsigned int)ctr->curr_sec;
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if (_curr_sec & 0x80000000)
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continue;
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curr = (volatile unsigned int)ctr->curr_ctr;
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past = (volatile unsigned int)ctr->prev_ctr;
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curr_sec = (volatile unsigned int)ctr->curr_sec;
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if (_curr == curr && _past == past && _curr_sec == curr_sec)
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break;
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}
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age = now.tv_sec - curr_sec;
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if (unlikely(age > 1))
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@ -64,18 +67,21 @@ unsigned int read_freq_ctr(struct freq_ctr *ctr)
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*/
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unsigned int freq_ctr_remain(struct freq_ctr *ctr, unsigned int freq, unsigned int pend)
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{
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unsigned int curr, past;
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unsigned int age, curr_sec;
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unsigned int curr, past, _curr, _past;
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unsigned int age, curr_sec, _curr_sec;
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do {
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curr = ctr->curr_ctr;
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past = ctr->prev_ctr;
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curr_sec = ctr->curr_sec;
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} while (curr != ctr->curr_ctr
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|| past != ctr->prev_ctr
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|| curr_sec != ctr->curr_sec
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|| (curr_sec & 0x80000000));
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while(1) {
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_curr = (volatile unsigned int)ctr->curr_ctr;
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_past = (volatile unsigned int)ctr->prev_ctr;
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_curr_sec = (volatile unsigned int)ctr->curr_sec;
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if (_curr_sec & 0x80000000)
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continue;
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curr = (volatile unsigned int)ctr->curr_ctr;
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past = (volatile unsigned int)ctr->prev_ctr;
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curr_sec = (volatile unsigned int)ctr->curr_sec;
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if (_curr == curr && _past == past && _curr_sec == curr_sec)
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break;
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}
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age = now.tv_sec - curr_sec;
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if (unlikely(age > 1))
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@ -102,18 +108,21 @@ unsigned int freq_ctr_remain(struct freq_ctr *ctr, unsigned int freq, unsigned i
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*/
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unsigned int next_event_delay(struct freq_ctr *ctr, unsigned int freq, unsigned int pend)
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{
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unsigned int curr, past;
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unsigned int wait, age, curr_sec;
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unsigned int curr, past, _curr, _past;
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unsigned int wait, age, curr_sec, _curr_sec;
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do {
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curr = ctr->curr_ctr;
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past = ctr->prev_ctr;
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curr_sec = ctr->curr_sec;
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} while (curr != ctr->curr_ctr
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|| past != ctr->prev_ctr
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|| curr_sec != ctr->curr_sec
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|| (curr_sec & 0x80000000));
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while(1) {
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_curr = (volatile unsigned int)ctr->curr_ctr;
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_past = (volatile unsigned int)ctr->prev_ctr;
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_curr_sec = (volatile unsigned int)ctr->curr_sec;
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if (_curr_sec & 0x80000000)
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continue;
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curr = (volatile unsigned int)ctr->curr_ctr;
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past = (volatile unsigned int)ctr->prev_ctr;
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curr_sec = (volatile unsigned int)ctr->curr_sec;
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if (_curr == curr && _past == past && _curr_sec == curr_sec)
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break;
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}
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age = now.tv_sec - curr_sec;
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if (unlikely(age > 1))
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@ -152,18 +161,21 @@ unsigned int next_event_delay(struct freq_ctr *ctr, unsigned int freq, unsigned
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*/
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unsigned int read_freq_ctr_period(struct freq_ctr_period *ctr, unsigned int period)
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{
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unsigned int curr, past;
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unsigned int remain, curr_tick;
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unsigned int _curr, _past, curr, past;
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unsigned int remain, _curr_tick, curr_tick;
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do {
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while(1) {
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_curr = ctr->curr_ctr;
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_past = ctr->prev_ctr;
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_curr_tick = ctr->curr_tick;
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if (_curr_tick & 0x1)
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continue;
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curr = ctr->curr_ctr;
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past = ctr->prev_ctr;
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curr_tick = ctr->curr_tick;
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} while (curr != ctr->curr_ctr
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|| past != ctr->prev_ctr
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|| curr_tick != ctr->curr_tick
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|| (curr_tick & 0x1));
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if (_curr == curr && _past == past && _curr_tick == curr_tick)
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break;
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};
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remain = curr_tick + period - now_ms;
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if (unlikely((int)remain < 0)) {
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@ -190,18 +202,21 @@ unsigned int read_freq_ctr_period(struct freq_ctr_period *ctr, unsigned int peri
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unsigned int freq_ctr_remain_period(struct freq_ctr_period *ctr, unsigned int period,
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unsigned int freq, unsigned int pend)
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{
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unsigned int curr, past;
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unsigned int remain, curr_tick;
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unsigned int _curr, _past, curr, past;
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unsigned int remain, _curr_tick, curr_tick;
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do {
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while(1) {
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_curr = ctr->curr_ctr;
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_past = ctr->prev_ctr;
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_curr_tick = ctr->curr_tick;
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if (_curr_tick & 0x1)
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continue;
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curr = ctr->curr_ctr;
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past = ctr->prev_ctr;
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curr_tick = ctr->curr_tick;
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} while (curr != ctr->curr_ctr
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|| past != ctr->prev_ctr
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|| curr_tick != ctr->curr_tick
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|| (curr_tick & 0x1));
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if (_curr == curr && _past == past && _curr_tick == curr_tick)
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break;
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};
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remain = curr_tick + period - now_ms;
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if (likely((int)remain < 0)) {
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