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BUG/MINOR: sink: fix a race condition between the writer and the reader 

This is the same issue as just fixed in b8e0fb97f ("BUG/MINOR: ring/cli:
fix a race condition between the writer and the reader") but this time
for sinks. They're also sucking the ring and present the same race at
high write loads.

This must be backported to 2.2 as well. See comments in the aforementioned
commit for backport hints if needed.
This commit is contained in:
Willy Tarreau 2022-08-04 17:18:54 +02:00
parent 96417f392d
commit 53bfab080c
1 changed files with 11 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
src/sink.c
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@ -306,7 +306,7 @@ static void sink_forward_io_handler(struct appctx *appctx)
struct ring *ring = sink->ctx.ring;
struct buffer *buf = &ring->buf;
uint64_t msg_len;
size_t len, cnt, ofs;
size_t len, cnt, ofs, last_ofs;
int ret = 0;
/* if stopping was requested, close immediately */
@ -409,6 +409,7 @@ static void sink_forward_io_handler(struct appctx *appctx)
HA_ATOMIC_INC(b_peek(buf, ofs));
ofs += ring->ofs;
sft->ofs = ofs;
last_ofs = ring->ofs;
}
HA_RWLOCK_RDUNLOCK(LOGSRV_LOCK, &ring->lock);
@ -416,8 +417,16 @@ static void sink_forward_io_handler(struct appctx *appctx)
/* let's be woken up once new data arrive */
HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
LIST_APPEND(&ring->waiters, &appctx->wait_entry);
ofs = ring->ofs;
HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
applet_have_no_more_data(appctx);
if (ofs != last_ofs) {
/* more data was added into the ring between the
* unlock and the lock, and the writer might not
* have seen us. We need to reschedule a read.
*/
applet_have_more_data(appctx);
} else
applet_have_no_more_data(appctx);
}
HA_SPIN_UNLOCK(SFT_LOCK, &sft->lock);