| From a3b21ce7625474ad67dd41b7ef1fa28bfeaa3317 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Mon, 22 Nov 2021 20:32:53 +0800 |
| Subject: net/smc: Avoid warning of possible recursive locking |
| |
| From: Wen Gu <guwen@linux.alibaba.com> |
| |
| [ Upstream commit 7a61432dc81375be06b02f0061247d3efbdfce3a ] |
| |
| Possible recursive locking is detected by lockdep when SMC |
| falls back to TCP. The corresponding warnings are as follows: |
| |
| ============================================ |
| WARNING: possible recursive locking detected |
| 5.16.0-rc1+ #18 Tainted: G E |
| -------------------------------------------- |
| wrk/1391 is trying to acquire lock: |
| ffff975246c8e7d8 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0x109/0x250 [smc] |
| |
| but task is already holding lock: |
| ffff975246c8f918 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0xfe/0x250 [smc] |
| |
| other info that might help us debug this: |
| Possible unsafe locking scenario: |
| |
| CPU0 |
| ---- |
| lock(&ei->socket.wq.wait); |
| lock(&ei->socket.wq.wait); |
| |
| *** DEADLOCK *** |
| |
| May be due to missing lock nesting notation |
| |
| 2 locks held by wrk/1391: |
| #0: ffff975246040130 (sk_lock-AF_SMC){+.+.}-{0:0}, at: smc_connect+0x43/0x150 [smc] |
| #1: ffff975246c8f918 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0xfe/0x250 [smc] |
| |
| stack backtrace: |
| Call Trace: |
| <TASK> |
| dump_stack_lvl+0x56/0x7b |
| __lock_acquire+0x951/0x11f0 |
| lock_acquire+0x27a/0x320 |
| ? smc_switch_to_fallback+0x109/0x250 [smc] |
| ? smc_switch_to_fallback+0xfe/0x250 [smc] |
| _raw_spin_lock_irq+0x3b/0x80 |
| ? smc_switch_to_fallback+0x109/0x250 [smc] |
| smc_switch_to_fallback+0x109/0x250 [smc] |
| smc_connect_fallback+0xe/0x30 [smc] |
| __smc_connect+0xcf/0x1090 [smc] |
| ? mark_held_locks+0x61/0x80 |
| ? __local_bh_enable_ip+0x77/0xe0 |
| ? lockdep_hardirqs_on+0xbf/0x130 |
| ? smc_connect+0x12a/0x150 [smc] |
| smc_connect+0x12a/0x150 [smc] |
| __sys_connect+0x8a/0xc0 |
| ? syscall_enter_from_user_mode+0x20/0x70 |
| __x64_sys_connect+0x16/0x20 |
| do_syscall_64+0x34/0x90 |
| entry_SYSCALL_64_after_hwframe+0x44/0xae |
| |
| The nested locking in smc_switch_to_fallback() is considered to |
| possibly cause a deadlock because smc_wait->lock and clc_wait->lock |
| are the same type of lock. But actually it is safe so far since |
| there is no other place trying to obtain smc_wait->lock when |
| clc_wait->lock is held. So the patch replaces spin_lock() with |
| spin_lock_nested() to avoid false report by lockdep. |
| |
| Link: https://lkml.org/lkml/2021/11/19/962 |
| Fixes: 2153bd1e3d3d ("Transfer remaining wait queue entries during fallback") |
| Reported-by: syzbot+e979d3597f48262cb4ee@syzkaller.appspotmail.com |
| Signed-off-by: Wen Gu <guwen@linux.alibaba.com> |
| Acked-by: Tony Lu <tonylu@linux.alibaba.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| net/smc/af_smc.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c |
| index 04bf8088872a9..d324a12c26cd9 100644 |
| --- a/net/smc/af_smc.c |
| +++ b/net/smc/af_smc.c |
| @@ -529,7 +529,7 @@ static void smc_switch_to_fallback(struct smc_sock *smc) |
| * to clcsocket->wq during the fallback. |
| */ |
| spin_lock_irqsave(&smc_wait->lock, flags); |
| - spin_lock(&clc_wait->lock); |
| + spin_lock_nested(&clc_wait->lock, SINGLE_DEPTH_NESTING); |
| list_splice_init(&smc_wait->head, &clc_wait->head); |
| spin_unlock(&clc_wait->lock); |
| spin_unlock_irqrestore(&smc_wait->lock, flags); |
| -- |
| 2.33.0 |
| |