On 2/9/19 7:34 PM, Jens Axboe wrote:
> On 2/9/19 6:11 PM, Matt Mullins wrote:
>> On Sat, 2019-02-09 at 17:47 -0700, Jens Axboe wrote:
>>> On 2/9/19 4:52 PM, Matt Mullins wrote:
>>>>> @@ -1292,6 +1338,154 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
>>>>> return READ_ONCE(ring->r.head) == READ_ONCE(ring->r.tail) ? ret : 0;
>>>>> }
>>>>>
>>>>> +static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
>>>>> +{
>>>>> +#if defined(CONFIG_UNIX)
>>>>> + if (ctx->ring_sock) {
>>>>> + struct sock *sock = ctx->ring_sock->sk;
>>>>> + struct sk_buff *skb;
>>>>> +
>>>>> + while ((skb = skb_dequeue(&sock->sk_receive_queue)) != NULL)
>>>>
>>>> Something's still a bit messy with destruction. I get a traceback here
>>>> while running
>>>>
>>>> int main() {
>>>> struct io_uring_params uring_params = {
>>>> .flags = IORING_SETUP_SQPOLL | IORING_SETUP_IOPOLL,
>>>> };
>>>> int uring_fd =
>>>> syscall(425 /* io_uring_setup */, 16, &uring_params);
>>>>
>>>> const __s32 fds[] = {1};
>>>>
>>>> syscall(427 /* io_uring_register */, uring_fd,
>>>> IORING_REGISTER_FILES, fds, sizeof(fds) / sizeof(*fds));
>>>> }
>>>>
>>>> I end up with the following spew:
>>>>
>>>> [ 195.983322] WARNING: CPU: 1 PID: 1938 at ../net/unix/af_unix.c:500 unix_sock_destructor+0x97/0xc0
>>>> [ 195.989556] Modules linked in:
>>>> [ 195.992738] CPU: 1 PID: 1938 Comm: aio_buffered Tainted: G W 5.0.0-rc5+ #379
>>>> [ 196.000926] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
>>>> [ 196.008316] RIP: 0010:unix_sock_destructor+0x97/0xc0
>>>> [ 196.010912] Code: 3f 37 f3 ff 5b 5d be 00 02 00 00 48 c7 c7 6c 5b 9a 81 e9 8c 2a 71 ff 48 89 ef e8 c4 dc 87 ff eb be 0f 0b 48 83 7b 70 00 74 8b <0f> 0b 48 83 bb 68 02 00 00 00 74 89 0f 0b eb 85 48 89 de 48 c7 c7
>>>> [ 196.018887] RSP: 0018:ffffc900008a7d40 EFLAGS: 00010282
>>>> [ 196.020754] RAX: 0000000000000000 RBX: ffff8881351dd000 RCX: 0000000000000000
>>>> [ 196.022811] RDX: 0000000000000001 RSI: 0000000000000282 RDI: 00000000ffffffff
>>>> [ 196.024901] RBP: ffff8881351dd000 R08: 0000000000024120 R09: ffffffff819a97fe
>>>> [ 196.026977] R10: ffffea0004cf6800 R11: 00000000005b8d80 R12: ffffffff81294ec2
>>>> [ 196.029119] R13: ffff888134e27b40 R14: ffff88813bb307a0 R15: ffff888133d59910
>>>> [ 196.031071] FS: 00007f1a8a8c3740(0000) GS:ffff88813bb00000(0000) knlGS:0000000000000000
>>>> [ 196.033069] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [ 196.034438] CR2: 00007f1a8aba5920 CR3: 000000000260e004 CR4: 00000000003606a0
>>>> [ 196.036310] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>> [ 196.038399] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>> [ 196.039794] Call Trace:
>>>> [ 196.040259] __sk_destruct+0x1c/0x150
>>>> [ 196.040964] ? io_sqe_files_unregister+0x32/0x70
>>>> [ 196.041841] unix_destruct_scm+0x76/0xa0
>>>> [ 196.042587] skb_release_head_state+0x38/0x60
>>>> [ 196.043401] skb_release_all+0x9/0x20
>>>> [ 196.044034] kfree_skb+0x2d/0xb0
>>>> [ 196.044603] io_sqe_files_unregister+0x32/0x70
>>>> [ 196.045385] io_ring_ctx_wait_and_kill+0xf6/0x1a0
>>>> [ 196.046220] io_uring_release+0x17/0x20
>>>> [ 196.046881] __fput+0x9d/0x1d0
>>>> [ 196.047421] task_work_run+0x7a/0x90
>>>> [ 196.048045] do_exit+0x301/0xc20
>>>> [ 196.048626] ? handle_mm_fault+0xf3/0x230
>>>> [ 196.049321] do_group_exit+0x35/0xa0
>>>> [ 196.049944] __x64_sys_exit_group+0xf/0x10
>>>> [ 196.050658] do_syscall_64+0x3d/0xf0
>>>> [ 196.051317] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>>> [ 196.052217] RIP: 0033:0x7f1a8aba5956
>>>> [ 196.052859] Code: Bad RIP value.
>>>> [ 196.053488] RSP: 002b:00007fffbdbcad38 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
>>>> [ 196.054902] RAX: ffffffffffffffda RBX: 00007f1a8ac975c0 RCX: 00007f1a8aba5956
>>>> [ 196.056124] RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
>>>> [ 196.057348] RBP: 0000000000000000 R08: 00000000000000e7 R09: ffffffffffffff78
>>>> [ 196.058573] R10: 00007fffbdbcabf8 R11: 0000000000000246 R12: 00007f1a8ac975c0
>>>> [ 196.059459] R13: 0000000000000001 R14: 00007f1a8aca0288 R15: 0000000000000000
>>>> [ 196.060731] ---[ end trace 8a7e42f9199e5f92 ]---
>>>> [ 196.062671] WARNING: CPU: 1 PID: 1938 at ../net/unix/af_unix.c:501 unix_sock_destructor+0xa3/0xc0
>>>> [ 196.064372] Modules linked in:
>>>> [ 196.064966] CPU: 1 PID: 1938 Comm: aio_buffered Tainted: G W 5.0.0-rc5+ #379
>>>> [ 196.066546] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
>>>> [ 196.068234] RIP: 0010:unix_sock_destructor+0xa3/0xc0
>>>> [ 196.068999] Code: c7 c7 6c 5b 9a 81 e9 8c 2a 71 ff 48 89 ef e8 c4 dc 87 ff eb be 0f 0b 48 83 7b 70 00 74 8b 0f 0b 48 83 bb 68 02 00 00 00 74 89 <0f> 0b eb 85 48 89 de 48 c7 c7 a0 c8 42 82 5b 5d e9 31 8c 75 ff 0f
>>>> [ 196.072577] RSP: 0018:ffffc900008a7d40 EFLAGS: 00010282
>>>> [ 196.073595] RAX: 0000000000000000 RBX: ffff8881351dd000 RCX: 0000000000000000
>>>> [ 196.074973] RDX: 0000000000000001 RSI: 0000000000000282 RDI: 00000000ffffffff
>>>> [ 196.076348] RBP: ffff8881351dd000 R08: 0000000000024120 R09: ffffffff819a97fe
>>>> [ 196.077709] R10: ffffea0004cf6800 R11: 00000000005b8d80 R12: ffffffff81294ec2
>>>> [ 196.079072] R13: ffff888134e27b40 R14: ffff88813bb307a0 R15: ffff888133d59910
>>>> [ 196.080441] FS: 00007f1a8a8c3740(0000) GS:ffff88813bb00000(0000) knlGS:0000000000000000
>>>> [ 196.082026] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [ 196.083131] CR2: 00007fbc19f96550 CR3: 0000000138d1e003 CR4: 00000000003606a0
>>>> [ 196.084505] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>> [ 196.085823] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>> [ 196.087185] Call Trace:
>>>> [ 196.087662] __sk_destruct+0x1c/0x150
>>>> [ 196.088376] ? io_sqe_files_unregister+0x32/0x70
>>>> [ 196.089299] unix_destruct_scm+0x76/0xa0
>>>> [ 196.090059] skb_release_head_state+0x38/0x60
>>>> [ 196.090929] skb_release_all+0x9/0x20
>>>> [ 196.091550] kfree_skb+0x2d/0xb0
>>>> [ 196.092745] io_sqe_files_unregister+0x32/0x70
>>>> [ 196.093535] io_ring_ctx_wait_and_kill+0xf6/0x1a0
>>>> [ 196.094358] io_uring_release+0x17/0x20
>>>> [ 196.095029] __fput+0x9d/0x1d0
>>>> [ 196.095660] task_work_run+0x7a/0x90
>>>> [ 196.096307] do_exit+0x301/0xc20
>>>> [ 196.096808] ? handle_mm_fault+0xf3/0x230
>>>> [ 196.097504] do_group_exit+0x35/0xa0
>>>> [ 196.098126] __x64_sys_exit_group+0xf/0x10
>>>> [ 196.098836] do_syscall_64+0x3d/0xf0
>>>> [ 196.099460] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>>> [ 196.100334] RIP: 0033:0x7f1a8aba5956
>>>> [ 196.100958] Code: Bad RIP value.
>>>> [ 196.101293] RSP: 002b:00007fffbdbcad38 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
>>>> [ 196.101933] RAX: ffffffffffffffda RBX: 00007f1a8ac975c0 RCX: 00007f1a8aba5956
>>>> [ 196.102535] RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
>>>> [ 196.103137] RBP: 0000000000000000 R08: 00000000000000e7 R09: ffffffffffffff78
>>>> [ 196.103739] R10: 00007fffbdbcabf8 R11: 0000000000000246 R12: 00007f1a8ac975c0
>>>> [ 196.104526] R13: 0000000000000001 R14: 00007f1a8aca0288 R15: 0000000000000000
>>>> [ 196.105777] ---[ end trace 8a7e42f9199e5f93 ]---
>>>> [ 196.107535] unix: Attempt to release alive unix socket: 000000003b3c1a34
>>>>
>>>> which corresponds to the WARN_ONs:
>>>>
>>>> WARN_ON(!sk_unhashed(sk));
>>>> WARN_ON(sk->sk_socket);
>>>>
>>>> This doesn't seem to happen if I omit the call to io_uring_register.
>>>
>>> Huh, I can't reproduce that here, teardown seems to work just fine. It
>>> looks like the socket is getting torn down prematurely, when we free the
>>> skb. I wonder if you have some networking options I don't? What's your
>>> .config?
>>>
>>
>> Interesting. Attached is the config I'm using to build
>> af22d31f8b09fa36f57569c95f4943febaacb2b1. I'll keep playing with it on
>> my end, too, maybe I've got something bad in my ccache.
>
> Bingo, reproduces with your .config. Looks like the io_uring is released
> basically as soon as we queue the skb in the socket. I'll take a look at
> this tomorrow.
OK, I think I see it. Apparently with my options, the size of the skb is
0 when I pass in 0. With your options, it's non-zero, which wreaks havoc
on the ref counting.
The below should fix it. I'll fold this in now.
diff --git a/fs/io_uring.c b/fs/io_uring.c
index d7a10484d748..c8794a11de3e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2006,6 +2006,7 @@ static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
fpl->max = fpl->count = nr;
UNIXCB(skb).fp = fpl;
+ refcount_add(skb->truesize, &ctx->ring_sock->sk->sk_wmem_alloc);
skb_queue_head(&ctx->ring_sock->sk->sk_receive_queue, skb);
for (i = 0; i < nr; i++)
--
Jens Axboe
