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.