BUG/MEDIUM: fd: maintain a per-thread update mask
Since the fd update tables are per-thread, we need to have a bit per
thread to indicate whether an update exists, otherwise this can lead
to lost update events every time multiple threads want to update the
same FD. In practice *for now*, it only happens at start time when
listeners are enabled and ask for polling after facing their first
EAGAIN. But since the pollers are still shared, a lost event is still
recovered by a neighbor thread. This will not reliably work anymore
with per-thread pollers, where it has been observed a few times on
startup that a single-threaded listener would not always accept
incoming connections upon startup.
It's worth noting that during this code review it appeared that the
"new" flag in the fdtab isn't used anymore.
This fix should be backported to 1.8.
diff --git a/include/types/fd.h b/include/types/fd.h
index 032bab9..54192e4 100644
--- a/include/types/fd.h
+++ b/include/types/fd.h
@@ -94,13 +94,13 @@
struct fdtab {
__decl_hathreads(HA_SPINLOCK_T lock);
unsigned long thread_mask; /* mask of thread IDs authorized to process the task */
+ unsigned long update_mask; /* mask of thread IDs having an update for fd */
void (*iocb)(int fd); /* I/O handler */
void *owner; /* the connection or listener associated with this fd, NULL if closed */
unsigned int cache; /* position+1 in the FD cache. 0=not in cache. */
unsigned char state; /* FD state for read and write directions (2*3 bits) */
unsigned char ev; /* event seen in return of poll() : FD_POLL_* */
unsigned char new:1; /* 1 if this fd has just been created */
- unsigned char updated:1; /* 1 if this fd is already in the update list */
unsigned char linger_risk:1; /* 1 if we must kill lingering before closing */
unsigned char cloned:1; /* 1 if a cloned socket, requires EPOLL_CTL_DEL on close */
};