5.4-stable review patch. If anyone has any objections, please let me know.
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From: Judy Hsiao judyhsiao@chromium.org
[ Upstream commit e5dc5afff62f3e97e86c3643ec9fcad23de4f2d3 ]
We are seeing cases where neigh_cleanup_and_release() is called by neigh_forced_gc() many times in a row with preemption turned off. When running on a low powered CPU at a low CPU frequency, this has been measured to keep preemption off for ~10 ms. That's not great on a system with HZ=1000 which expects tasks to be able to schedule in with ~1ms latency.
Suggested-by: Douglas Anderson dianders@chromium.org Signed-off-by: Judy Hsiao judyhsiao@chromium.org Reviewed-by: David Ahern dsahern@kernel.org Reviewed-by: Eric Dumazet edumazet@google.com Reviewed-by: Douglas Anderson dianders@chromium.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/neighbour.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 9d631b7adb7b..e571007d083c 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -226,9 +226,11 @@ static int neigh_forced_gc(struct neigh_table *tbl) { int max_clean = atomic_read(&tbl->gc_entries) - READ_ONCE(tbl->gc_thresh2); + u64 tmax = ktime_get_ns() + NSEC_PER_MSEC; unsigned long tref = jiffies - 5 * HZ; struct neighbour *n, *tmp; int shrunk = 0; + int loop = 0;
NEIGH_CACHE_STAT_INC(tbl, forced_gc_runs);
@@ -251,11 +253,16 @@ static int neigh_forced_gc(struct neigh_table *tbl) shrunk++; if (shrunk >= max_clean) break; + if (++loop == 16) { + if (ktime_get_ns() > tmax) + goto unlock; + loop = 0; + } } }
WRITE_ONCE(tbl->last_flush, jiffies); - +unlock: write_unlock_bh(&tbl->lock);
return shrunk;