Subject: Re: [PATCH 1/1] virtio_net: Add timeout handler to avoid kernel hang

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 18 Jan 2024 08:14:21 -0500

On Tue, Jan 16, 2024 at 01:04:49PM +0100, Paolo Abeni wrote:
> On Mon, 2024-01-15 at 09:29 +0800, Zhu Yanjun wrote:
> > From: Zhu Yanjun <[email-masked]>
> > 
> > Some devices emulate the virtio_net hardwares. When virtio_net
> > driver sends commands to the emulated hardware, normally the
> > hardware needs time to response. Sometimes the time is very
> > long. Thus, the following will appear. Then the whole system
> > will hang.
> > The similar problems also occur in Intel NICs and Mellanox NICs.
> > As such, the similar solution is borrowed from them. A timeout
> > value is added and the timeout value as large as possible is set
> > to ensure that the driver gets the maximum possible response from
> > the hardware.
> > 
> > "
> > [  213.795860] watchdog: BUG: soft lockup - CPU#108 stuck for 26s! [(udev-worker):3157]
> > [  213.796114] Modules linked in: virtio_net(+) net_failover failover qrtr rfkill sunrpc intel_rapl_msr intel_rapl_common intel_uncore_frequency intel_uncore_frequency_common intel_ifs i10nm_edac nfit libnvdimm x86_pkg_temp_thermal intel_powerclamp coretemp iTCO_wdt rapl intel_pmc_bxt dax_hmem iTCO_vendor_support vfat cxl_acpi intel_cstate pmt_telemetry pmt_class intel_sdsi joydev intel_uncore cxl_core fat pcspkr mei_me isst_if_mbox_pci isst_if_mmio idxd i2c_i801 isst_if_common mei intel_vsec idxd_bus i2c_smbus i2c_ismt ipmi_ssif acpi_ipmi ipmi_si ipmi_devintf ipmi_msghandler acpi_pad acpi_power_meter pfr_telemetry pfr_update fuse loop zram xfs crct10dif_pclmul crc32_pclmul crc32c_intel polyval_clmulni polyval_generic ghash_clmulni_intel sha512_ssse3 bnxt_en sha256_ssse3 sha1_ssse3 nvme ast nvme_core i2c_algo_bit wmi pinctrl_emmitsburg scsi_dh_rdac scsi_dh_emc scsi_dh_alua dm_multipath
> > [  213.796194] irq event stamp: 67740
> > [  213.796195] hardirqs last  enabled at (67739): [<ffffffff8c2015ca>] asm_sysvec_apic_timer_interrupt+0x1a/0x20
> > [  213.796203] hardirqs last disabled at (67740): [<ffffffff8c14108e>] sysvec_apic_timer_interrupt+0xe/0x90
> > [  213.796208] softirqs last  enabled at (67686): [<ffffffff8b12115e>] __irq_exit_rcu+0xbe/0xe0
> > [  213.796214] softirqs last disabled at (67681): [<ffffffff8b12115e>] __irq_exit_rcu+0xbe/0xe0
> > [  213.796217] CPU: 108 PID: 3157 Comm: (udev-worker) Kdump: loaded Not tainted 6.7.0+ #9
> > [  213.796220] Hardware name: Intel Corporation M50FCP2SBSTD/M50FCP2SBSTD, BIOS SE5C741.86B.01.01.0001.2211140926 11/14/2022
> > [  213.796221] RIP: 0010:virtqueue_get_buf_ctx_split+0x8d/0x110
> > [  213.796228] Code: 89 df e8 26 fe ff ff 0f b7 43 50 83 c0 01 66 89 43 50 f6 43 78 01 75 12 80 7b 42 00 48 8b 4b 68 8b 53 58 74 0f 66 87 44 51 04 <48> 89 e8 5b 5d c3 cc cc cc cc 66 89 44 51 04 0f ae f0 48 89 e8 5b
> > [  213.796230] RSP: 0018:ff4bbb362306f9b0 EFLAGS: 00000246
> > [  213.796233] RAX: 0000000000000000 RBX: ff2f15095896f000 RCX: 0000000000000001
> > [  213.796235] RDX: 0000000000000000 RSI: ff4bbb362306f9cc RDI: ff2f15095896f000
> > [  213.796236] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> > [  213.796237] R10: 0000000000000003 R11: ff2f15095893cc40 R12: 0000000000000002
> > [  213.796239] R13: 0000000000000004 R14: 0000000000000000 R15: ff2f1509534f3000
> > [  213.796240] FS:  00007f775847d0c0(0000) GS:ff2f1528bac00000(0000) knlGS:0000000000000000
> > [  213.796242] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [  213.796243] CR2: 0000557f987b6e70 CR3: 0000002098602006 CR4: 0000000000f71ef0
> > [  213.796245] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > [  213.796246] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
> > [  213.796247] PKRU: 55555554
> > [  213.796249] Call Trace:
> > [  213.796250]  <IRQ>
> > [  213.796252]  ? watchdog_timer_fn+0x1c0/0x220
> > [  213.796258]  ? __pfx_watchdog_timer_fn+0x10/0x10
> > [  213.796261]  ? __hrtimer_run_queues+0x1af/0x380
> > [  213.796269]  ? hrtimer_interrupt+0xf8/0x230
> > [  213.796274]  ? __sysvec_apic_timer_interrupt+0x64/0x1a0
> > [  213.796279]  ? sysvec_apic_timer_interrupt+0x6d/0x90
> > [  213.796282]  </IRQ>
> > [  213.796284]  <TASK>
> > [  213.796285]  ? asm_sysvec_apic_timer_interrupt+0x1a/0x20
> > [  213.796293]  ? virtqueue_get_buf_ctx_split+0x8d/0x110
> > [  213.796297]  virtnet_send_command+0x18a/0x1f0 [virtio_net]
> > [  213.796310]  _virtnet_set_queues+0xc6/0x120 [virtio_net]
> > [  213.796319]  virtnet_probe+0xa06/0xd50 [virtio_net]
> > [  213.796328]  virtio_dev_probe+0x195/0x230
> > [  213.796333]  really_probe+0x19f/0x400
> > [  213.796338]  ? __pfx___driver_attach+0x10/0x10
> > [  213.796340]  __driver_probe_device+0x78/0x160
> > [  213.796343]  driver_probe_device+0x1f/0x90
> > [  213.796346]  __driver_attach+0xd6/0x1d0
> > [  213.796349]  bus_for_each_dev+0x8c/0xe0
> > [  213.796355]  bus_add_driver+0x119/0x220
> > [  213.796359]  driver_register+0x59/0x100
> > [  213.796362]  ? __pfx_virtio_net_driver_init+0x10/0x10 [virtio_net]
> > [  213.796369]  virtio_net_driver_init+0x8e/0xff0 [virtio_net]
> > [  213.796375]  do_one_initcall+0x6f/0x380
> > [  213.796384]  do_init_module+0x60/0x240
> > [  213.796388]  init_module_from_file+0x86/0xc0
> > [  213.796396]  idempotent_init_module+0x129/0x2c0
> > [  213.796406]  __x64_sys_finit_module+0x5e/0xb0
> > [  213.796409]  do_syscall_64+0x60/0xe0
> > [  213.796415]  ? do_syscall_64+0x6f/0xe0
> > [  213.796418]  ? lockdep_hardirqs_on_prepare+0xe4/0x1a0
> > [  213.796424]  ? do_syscall_64+0x6f/0xe0
> > [  213.796427]  ? do_syscall_64+0x6f/0xe0
> > [  213.796431]  entry_SYSCALL_64_after_hwframe+0x6e/0x76
> > [  213.796435] RIP: 0033:0x7f7758f279cd
> > [  213.796465] Code: 5d c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 33 e4 0c 00 f7 d8 64 89 01 48
> > [  213.796467] RSP: 002b:00007ffe2cad8738 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
> > [  213.796469] RAX: ffffffffffffffda RBX: 0000557f987a8180 RCX: 00007f7758f279cd
> > [  213.796471] RDX: 0000000000000000 RSI: 00007f77593e5453 RDI: 000000000000000f
> > [  213.796472] RBP: 00007f77593e5453 R08: 0000000000000000 R09: 00007ffe2cad8860
> > [  213.796473] R10: 000000000000000f R11: 0000000000000246 R12: 0000000000020000
> > [  213.796475] R13: 0000557f9879f8e0 R14: 0000000000000000 R15: 0000557f98783aa0
> > [  213.796482]  </TASK>
> > "
> > 
> > Signed-off-by: Zhu Yanjun <[email-masked]>
> > ---
> >  drivers/net/virtio_net.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 51b1868d2f22..28b7dd917a43 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -2468,7 +2468,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
> >  {
> >  	struct scatterlist *sgs[4], hdr, stat;
> >  	unsigned out_num = 0, tmp;
> > -	int ret;
> > +	int ret, timeout = 200;
> >  
> >  	/* Caller should know better */
> >  	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
> > @@ -2502,8 +2502,14 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
> >  	 * into the hypervisor, so the request should be handled immediately.
> >  	 */
> >  	while (!virtqueue_get_buf(vi->cvq, &tmp) &&
> > -	       !virtqueue_is_broken(vi->cvq))
> > +	       !virtqueue_is_broken(vi->cvq)) {
> > +		if (timeout)
> > +			timeout--;
> 
> This is not really a timeout, just a loop counter. 200 iterations could
> be a very short time on reasonable H/W. I guess this avoid the soft
> lockup, but possibly (likely?) breaks the functionality when we need to
> loop for some non negligible time.
> 
> I fear we need a more complex solution, as mentioned by Micheal in the
> thread you quoted.
> 
> Cheers,
> 
> Paolo

So a bunch of devices just queue a rquest on a workqueue. Problem is,
errors are not reported then. I really feel this is something netdev
core should support better: return a "deferred" status and have
netdev core wait outside a lock on a waitqueue.

-- 
MST