diff options
| author | Eric Dumazet <edumazet@google.com> | 2024-08-24 18:19:01 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2024-08-27 08:20:45 -0700 |
| commit | bc21000e99f92a6b5540d7267c6b22806c5c33d3 (patch) | |
| tree | 6b9d75cc4df99c20abae1cc4abaa4f652cbc757b /net | |
| parent | 4786fe29f5a0dd74d9ccdce8c734bde1fb88cf37 (diff) | |
net_sched: sch_fq: fix incorrect behavior for small weights
fq_dequeue() has a complex logic to find packets in one of the 3 bands.
As Neal found out, it is possible that one band has a deficit smaller
than its weight. fq_dequeue() can return NULL while some packets are
elligible for immediate transmit.
In this case, more than one iteration is needed to refill pband->credit.
With default parameters (weights 589824 196608 65536) bug can trigger
if large BIG TCP packets are sent to the lowest priority band.
Bisected-by: John Sperbeck <jsperbeck@google.com>
Diagnosed-by: Neal Cardwell <ncardwell@google.com>
Fixes: 29f834aa326e ("net_sched: sch_fq: add 3 bands and WRR scheduling")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20240824181901.953776-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/sched/sch_fq.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c index 238974725679..19a49af5a9e5 100644 --- a/net/sched/sch_fq.c +++ b/net/sched/sch_fq.c @@ -663,7 +663,9 @@ begin: pband = &q->band_flows[q->band_nr]; pband->credit = min(pband->credit + pband->quantum, pband->quantum); - goto begin; + if (pband->credit > 0) + goto begin; + retry = 0; } if (q->time_next_delayed_flow != ~0ULL) qdisc_watchdog_schedule_range_ns(&q->watchdog, |