Hello there.
Recently I tried a couple of commands below on the kernel v6.6 and v6.7-rc1,
then observed a lockdep WARN at the second command [1]. The first command
removes a PCI device, and the second command rescans whole PCI devices to
regain the removed device.
# echo 1 > /sys/bus/pci/devices/0000:51:00.0/remove
# echo 1 > /sys/bus/pci/rescan
I tried this rescan for SAS-HBA or AHCI controller with HDDs. When those devices
are left in weird status after some kernel tests, I want to remove the SAS-HBA
and AHCI controller and rescan to get back the devices in good status. This
rescan looks working good except the WARN.
The lockdep splat indicates possible deadlock between pci_rescan_remove_lock
and work_completion lock have deadlock possibility. Is the lockdep WARN a known
issue? I found a similar discussion in the past [2], but it did not discuss the
work_completion lock, so my observation looks a new, different issue.
In the call stack, I found that the workqueue thread for i801_probe() calls
p2sb_bar(), which locks pci_rescan_remove_lock. IMHO, the issue cause looks that
pci_rescan_remove_lock is locked in both workqueue context and non-workqueue
context. As a fix trial, I created a quick patch [3]. It calls i801_probe() in
non-workqueue context only by adding a new flag to struct pci_driver. With this,
I observed the lockdep WARN disappears. Is this a good solution approach? If
not, is there any other better solution?
[1] kernel message log at the second command
[ 242.922091] ======================================================
[ 242.931663] WARNING: possible circular locking dependency detected
[ 242.938292] mpt3sas_cm1: 63 BIT PCI BUS DMA ADDRESSING SUPPORTED, total mem (56799464 kB)
[ 242.939415] 6.7.0-rc1-kts #1 Not tainted
[ 242.939419] ------------------------------------------------------
[ 242.939421] bash/1615 is trying to acquire lock:
[ 242.939424] ff1100017bf87910 ((work_completion)(&wfc.work)){+.+.}-{0:0}, at: __flush_work+0xc5/0x980
[ 242.989069]
but task is already holding lock:
[ 243.000283] ffffffff870bf4a8 (pci_rescan_remove_lock){+.+.}-{3:3}, at: rescan_store+0x96/0xd0
[ 243.012269]
which lock already depends on the new lock.
[ 243.028569]
the existing dependency chain (in reverse order) is:
[ 243.041611]
-> #1 (pci_rescan_remove_lock){+.+.}-{3:3}:
[ 243.053709] __mutex_lock+0x16a/0x1880
[ 243.060767] p2sb_bar+0xa7/0x250
[ 243.067213] i801_add_tco_spt.constprop.0+0x88/0x1f0 [i2c_i801]
[ 243.076707] i801_add_tco+0x18a/0x210 [i2c_i801]
[ 243.084727] i801_probe+0x99c/0x1500 [i2c_i801]
[ 243.092618] local_pci_probe+0xd6/0x190
[ 243.099708] work_for_cpu_fn+0x4e/0xa0
[ 243.106673] process_one_work+0x736/0x1230
[ 243.114012] worker_thread+0x723/0x1300
[ 243.121039] kthread+0x2ee/0x3d0
[ 243.127372] ret_from_fork+0x2d/0x70
[ 243.134073] ret_from_fork_asm+0x1b/0x30
[ 243.141140]
-> #0 ((work_completion)(&wfc.work)){+.+.}-{0:0}:
[ 243.153341] __lock_acquire+0x2e74/0x5ea0
[ 243.160490] lock_acquire+0x196/0x4b0
[ 243.167236] __flush_work+0xe2/0x980
[ 243.173882] work_on_cpu_key+0xcc/0xf0
[ 243.180709] pci_device_probe+0x548/0x740
[ 243.187813] really_probe+0x3df/0xb80
[ 243.194525] __driver_probe_device+0x18c/0x450
[ 243.202128] driver_probe_device+0x4a/0x120
[ 243.209437] __device_attach_driver+0x15e/0x270
[ 243.217149] bus_for_each_drv+0x101/0x170
[ 243.224260] __device_attach+0x189/0x380
[ 243.231254] pci_bus_add_device+0x9f/0xf0
[ 243.238360] pci_bus_add_devices+0x7f/0x190
[ 243.245639] pci_bus_add_devices+0x114/0x190
[ 243.253017] pci_rescan_bus+0x23/0x30
[ 243.259711] rescan_store+0xa2/0xd0
[ 243.266187] kernfs_fop_write_iter+0x356/0x530
[ 243.273735] vfs_write+0x513/0xd60
[ 243.280090] ksys_write+0xe7/0x1b0
[ 243.286412] do_syscall_64+0x5d/0xe0
[ 243.292908] entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 243.301053]
other info that might help us debug this:
[ 243.315550] Possible unsafe locking scenario:
[ 243.325803] CPU0 CPU1
[ 243.332654] ---- ----
[ 243.339492] lock(pci_rescan_remove_lock);
[ 243.345937] lock((work_completion)(&wfc.work));
[ 243.355852] lock(pci_rescan_remove_lock);
[ 243.365170] lock((work_completion)(&wfc.work));
[ 243.372235]
*** DEADLOCK ***
[ 243.384100] 5 locks held by bash/1615:
[ 243.390048] #0: ff1100013f4b0418 (sb_writers#4){.+.+}-{0:0}, at: ksys_write+0xe7/0x1b0
[ 243.400833] #1: ff11000128429888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x21d/0x530
[ 243.412623] #2: ff11000103849968 (kn->active#136){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x241/0x530
[ 243.424832] #3: ffffffff870bf4a8 (pci_rescan_remove_lock){+.+.}-{3:3}, at: rescan_store+0x96/0xd0
[ 243.436773] #4: ff1100019cc7e1a8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x67/0x380
[ 243.448048]
stack backtrace:
[ 243.456654] CPU: 16 PID: 1615 Comm: bash Not tainted 6.7.0-rc1-kts #1
[ 243.465797] Hardware name: Supermicro SYS-520P-WTR/X12SPW-TF, BIOS 1.2 02/14/2022
[ 243.476145] Call Trace:
[ 243.480820] <TASK>
[ 243.485084] dump_stack_lvl+0x57/0x90
[ 243.491112] check_noncircular+0x2e1/0x3c0
[ 243.497630] ? __pfx_check_noncircular+0x10/0x10
[ 243.504747] ? __pfx___bfs+0x10/0x10
[ 243.510680] ? lockdep_lock+0xbc/0x1a0
[ 243.516811] ? __pfx_lockdep_lock+0x10/0x10
[ 243.523436] __lock_acquire+0x2e74/0x5ea0
[ 243.529866] ? __pfx___lock_acquire+0x10/0x10
[ 243.536682] lock_acquire+0x196/0x4b0
[ 243.542710] ? __flush_work+0xc5/0x980
[ 243.548829] ? __pfx_lock_acquire+0x10/0x10
[ 243.555442] ? __pfx___lock_acquire+0x10/0x10
[ 243.562252] ? driver_probe_device+0x4a/0x120
[ 243.569061] ? __device_attach_driver+0x15e/0x270
[ 243.576282] ? mark_lock+0xee/0x16c0
[ 243.582222] ? __flush_work+0xc5/0x980
[ 243.588364] __flush_work+0xe2/0x980
[ 243.594300] ? __flush_work+0xc5/0x980
[ 243.600425] ? __queue_work+0x4e4/0xe30
[ 243.606658] ? __pfx___flush_work+0x10/0x10
[ 243.613287] ? lock_is_held_type+0xce/0x120
[ 243.619917] ? queue_work_on+0x69/0xa0
[ 243.626032] ? lockdep_hardirqs_on+0x7d/0x100
[ 243.632834] work_on_cpu_key+0xcc/0xf0
[ 243.638950] ? __pfx_work_on_cpu_key+0x10/0x10
[ 243.645849] ? __pfx_work_for_cpu_fn+0x10/0x10
[ 243.652738] ? __pfx_local_pci_probe+0x10/0x10
[ 243.659638] pci_device_probe+0x548/0x740
[ 243.666057] ? __pfx_pci_device_probe+0x10/0x10
[ 243.673057] ? kernfs_create_link+0x167/0x230
[ 243.679855] really_probe+0x3df/0xb80
[ 243.685860] __driver_probe_device+0x18c/0x450
[ 243.692737] driver_probe_device+0x4a/0x120
[ 243.699314] __device_attach_driver+0x15e/0x270
[ 243.706297] ? __pfx___device_attach_driver+0x10/0x10
[ 243.713890] bus_for_each_drv+0x101/0x170
[ 243.720312] ? __pfx_bus_for_each_drv+0x10/0x10
[ 243.727294] ? lockdep_hardirqs_on+0x7d/0x100
[ 243.734063] ? _raw_spin_unlock_irqrestore+0x35/0x60
[ 243.741505] __device_attach+0x189/0x380
[ 243.747747] ? __pfx___device_attach+0x10/0x10
[ 243.754554] pci_bus_add_device+0x9f/0xf0
[ 243.760836] pci_bus_add_devices+0x7f/0x190
[ 243.767328] pci_bus_add_devices+0x114/0x190
[ 243.773890] pci_rescan_bus+0x23/0x30
[ 243.779741] rescan_store+0xa2/0xd0
[ 243.785362] ? __pfx_rescan_store+0x10/0x10
[ 243.791785] kernfs_fop_write_iter+0x356/0x530
[ 243.798516] vfs_write+0x513/0xd60
[ 243.804054] ? __pfx_vfs_write+0x10/0x10
[ 243.810193] ? __fget_light+0x51/0x220
[ 243.816125] ? __pfx_lock_release+0x10/0x10
[ 243.822555] ksys_write+0xe7/0x1b0
[ 243.828097] ? __pfx_ksys_write+0x10/0x10
[ 243.834327] ? syscall_enter_from_user_mode+0x22/0x90
[ 243.841736] ? lockdep_hardirqs_on+0x7d/0x100
[ 243.848366] do_syscall_64+0x5d/0xe0
[ 243.854114] ? do_syscall_64+0x6c/0xe0
[ 243.860053] ? do_syscall_64+0x6c/0xe0
[ 243.865989] ? lockdep_hardirqs_on+0x7d/0x100
[ 243.872608] ? do_syscall_64+0x6c/0xe0
[ 243.878537] ? lockdep_hardirqs_on+0x7d/0x100
[ 243.885147] entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 243.892555] RIP: 0033:0x7fee10d53c34
[ 243.898305] Code: c7 00 16 00 00 00 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 80 3d 35 77 0d 00 00 74 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 55 48 89 e5 48 83 ec 20 48 89
[ 243.922266] RSP: 002b:00007ffd173e68e8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
[ 243.932655] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fee10d53c34
[ 243.942564] RDX: 0000000000000002 RSI: 000055f17c9c4bc0 RDI: 0000000000000001
[ 243.952485] RBP: 00007ffd173e6910 R08: 0000000000000073 R09: 0000000000000001
[ 243.962408] R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000002
[ 243.972328] R13: 000055f17c9c4bc0 R14: 00007fee10e245c0 R15: 00007fee10e21f20
[ 243.982259] </TASK>
[2] https://patchwork.kernel.org/project/linux-pci/patch/20180921205752.3191-1-keith.busch@xxxxxxxxx/
[3] fix trial patch
diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 070999139c6..00d57d4e006 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -1820,6 +1820,7 @@ static struct pci_driver i801_driver = {
.pm = pm_sleep_ptr(&i801_pm_ops),
.probe_type = PROBE_PREFER_ASYNCHRONOUS,
},
+ .local_probe = true,
};
static int __init i2c_i801_init(struct pci_driver *drv)
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 51ec9e7e784..161ff37143a 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -368,7 +368,7 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
* device is probed from work_on_cpu() of the Physical device.
*/
if (node < 0 || node >= MAX_NUMNODES || !node_online(node) ||
- pci_physfn_is_probed(dev)) {
+ pci_physfn_is_probed(dev) || drv->local_probe) {
cpu = nr_cpu_ids;
} else {
cpumask_var_t wq_domain_mask;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 60ca768bc86..6fd086eb26c 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -957,6 +957,7 @@ struct pci_driver {
struct device_driver driver;
struct pci_dynids dynids;
bool driver_managed_dma;
+ bool local_probe;
};
static inline struct pci_driver *to_pci_driver(struct device_driver *drv)
