diff options
| author | Eric Dumazet <edumazet@google.com> | 2022-05-16 07:24:53 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2022-05-16 13:33:59 +0300 |
| commit | 97e719a82b43c6c2bb5eebdb3c5d479a332ac2ac (patch) | |
| tree | 7e38c6a88703169d84365cb91c9aaab5aabe0adb /net/core/dev.c | |
| parent | 3daebfbeb4555cb0c113aeb88aa469192ee41d89 (diff) | |
| download | linux-97e719a82b43c6c2bb5eebdb3c5d479a332ac2ac.tar.xz | |
net: fix possible race in skb_attempt_defer_free()
A cpu can observe sd->defer_count reaching 128,
and call smp_call_function_single_async()
Problem is that the remote CPU can clear sd->defer_count
before the IPI is run/acknowledged.
Other cpus can queue more packets and also decide
to call smp_call_function_single_async() while the pending
IPI was not yet delivered.
This is a common issue with smp_call_function_single_async().
Callers must ensure correct synchronization and serialization.
I triggered this issue while experimenting smaller threshold.
Performing the call to smp_call_function_single_async()
under sd->defer_lock protection did not solve the problem.
Commit 5a18ceca6350 ("smp: Allow smp_call_function_single_async()
to insert locked csd") replaced an informative WARN_ON_ONCE()
with a return of -EBUSY, which is often ignored.
Test of CSD_FLAG_LOCK presence is racy anyway.
Fixes: 68822bdf76f1 ("net: generalize skb freeing deferral to per-cpu lists")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/dev.c')
| -rw-r--r-- | net/core/dev.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index d93456c75b55..a5e663e1a75a 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4582,9 +4582,12 @@ static void rps_trigger_softirq(void *data) #endif /* CONFIG_RPS */ /* Called from hardirq (IPI) context */ -static void trigger_rx_softirq(void *data __always_unused) +static void trigger_rx_softirq(void *data) { + struct softnet_data *sd = data; + __raise_softirq_irqoff(NET_RX_SOFTIRQ); + smp_store_release(&sd->defer_ipi_scheduled, 0); } /* @@ -11382,7 +11385,7 @@ static int __init net_dev_init(void) INIT_CSD(&sd->csd, rps_trigger_softirq, sd); sd->cpu = i; #endif - INIT_CSD(&sd->defer_csd, trigger_rx_softirq, NULL); + INIT_CSD(&sd->defer_csd, trigger_rx_softirq, sd); spin_lock_init(&sd->defer_lock); init_gro_hash(&sd->backlog); |