diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2024-06-20 15:21:58 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2024-06-24 16:41:23 -0700 |
| commit | ecefbc09e8ee768ae85b7bb7a1de8c8287397d68 (patch) | |
| tree | 10fb21f193ef0986499840b54a3ed41254cfea6f /net/core/dev.c | |
| parent | c67ef53a88db5bcc29a6da20dcbc09206d49d0a9 (diff) | |
net: softnet_data: Make xmit per task.
Softirq is preemptible on PREEMPT_RT. Without a per-CPU lock in
local_bh_disable() there is no guarantee that only one device is
transmitting at a time.
With preemption and multiple senders it is possible that the per-CPU
`recursion' counter gets incremented by different threads and exceeds
XMIT_RECURSION_LIMIT leading to a false positive recursion alert.
The `more' member is subject to similar problems if set by one thread
for one driver and wrongly used by another driver within another thread.
Instead of adding a lock to protect the per-CPU variable it is simpler
to make xmit per-task. Sending and receiving skbs happens always
in thread context anyway.
Having a lock to protected the per-CPU counter would block/ serialize two
sending threads needlessly. It would also require a recursive lock to
ensure that the owner can increment the counter further.
Make the softnet_data.xmit a task_struct member on PREEMPT_RT. Add
needed wrapper.
Cc: Ben Segall <bsegall@google.com>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20240620132727.660738-9-bigeasy@linutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/core/dev.c')
| -rw-r--r-- | net/core/dev.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index 093d82bf0e28..95b9e4cc1767 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3940,6 +3940,7 @@ netdev_tx_queue_mapping(struct net_device *dev, struct sk_buff *skb) return netdev_get_tx_queue(dev, netdev_cap_txqueue(dev, qm)); } +#ifndef CONFIG_PREEMPT_RT static bool netdev_xmit_txqueue_skipped(void) { return __this_cpu_read(softnet_data.xmit.skip_txqueue); @@ -3950,6 +3951,19 @@ void netdev_xmit_skip_txqueue(bool skip) __this_cpu_write(softnet_data.xmit.skip_txqueue, skip); } EXPORT_SYMBOL_GPL(netdev_xmit_skip_txqueue); + +#else +static bool netdev_xmit_txqueue_skipped(void) +{ + return current->net_xmit.skip_txqueue; +} + +void netdev_xmit_skip_txqueue(bool skip) +{ + current->net_xmit.skip_txqueue = skip; +} +EXPORT_SYMBOL_GPL(netdev_xmit_skip_txqueue); +#endif #endif /* CONFIG_NET_EGRESS */ #ifdef CONFIG_NET_XGRESS |