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BUG/MINOR: server/idle: at least use atomic stores when updating max_used_conns

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In 2.2, some idle conns usage metrics were added by commit cf612a045
("MINOR: servers: Add a counter for the number of currently used
connections."), which mentioned that the operation doesn't need to be
atomic since we're not seeking exact values. This is true but at least
we should use atomic stores to make sure not to cause invalid values
to appear on archs that wouldn't guarantee atomicity when writing an
int, such as writing two 16-bit words. This is pretty unlikely on our
targets but better keep the code safe against this.

This may be backported as far as 2.2.

(cherry picked from commit 9dc231a6b23fc7d5cf3c233b46e00b9e251325b4)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
This commit is contained in:
Willy Tarreau 2022-11-21 14:32:33 +01:00 committed by Christopher Faulet
parent 21301a0d7c
commit 51743eea8b
2 changed files with 9 additions and 6 deletions
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13
include/haproxy/server.h
View File

@ -264,18 +264,21 @@ static inline enum srv_initaddr srv_get_next_initaddr(unsigned int *list)
static inline void srv_use_conn(struct server *srv, struct connection *conn)
{
unsigned int curr;
unsigned int curr, prev;
curr = _HA_ATOMIC_ADD_FETCH(&srv->curr_used_conns, 1);
/* It's ok not to do that atomically, we don't need an
* exact max.
*/
if (srv->max_used_conns < curr)
srv->max_used_conns = curr;
prev = HA_ATOMIC_LOAD(&srv->max_used_conns);
if (prev < curr)
HA_ATOMIC_STORE(&srv->max_used_conns, curr);
if (srv->est_need_conns < curr)
srv->est_need_conns = curr;
prev = HA_ATOMIC_LOAD(&srv->est_need_conns);
if (prev < curr)
HA_ATOMIC_STORE(&srv->est_need_conns, curr);
}
#endif /* _HAPROXY_SERVER_H */

2
src/server.c
View File

@ -5924,7 +5924,7 @@ struct task *srv_cleanup_idle_conns(struct task *task, void *context, unsigned i
if (srv->est_need_conns < srv->max_used_conns)
srv->est_need_conns = srv->max_used_conns;
srv->max_used_conns = srv->curr_used_conns;
HA_ATOMIC_STORE(&srv->max_used_conns, srv->curr_used_conns);
if (exceed_conns <= 0)
goto remove;