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s390/pci: Fix possible deadlock in recover_store()
With zpci_disable() working, lockdep detected a potential deadlock
(lockdep output at the end).
The deadlock is between recovering a PCI function via the
/sys/bus/pci/devices/<dev>/recover
attribute vs powering it off via
/sys/bus/pci/slots/<slot>/power.
The fix is analogous to the changes in commit 0ee223b2e1 ("scsi: core:
Avoid that SCSI device removal through sysfs triggers a deadlock")
that fixed a potential deadlock on removing a SCSI device via sysfs.
[ 204.830107] ======================================================
[ 204.830109] WARNING: possible circular locking dependency detected
[ 204.830111] 5.5.0-rc2-06072-gbc03ecc9a672 #6 Tainted: G W
[ 204.830112] ------------------------------------------------------
[ 204.830113] bash/1034 is trying to acquire lock:
[ 204.830115] 0000000192a1a610 (kn->count#200){++++}, at: kernfs_remove_by_name_ns+0x5c/0xa8
[ 204.830122]
but task is already holding lock:
[ 204.830123] 00000000c16134a8 (pci_rescan_remove_lock){+.+.}, at: pci_stop_and_remove_bus_device_locked+0x26/0x48
[ 204.830128]
which lock already depends on the new lock.
[ 204.830129]
the existing dependency chain (in reverse order) is:
[ 204.830130]
-> #1 (pci_rescan_remove_lock){+.+.}:
[ 204.830134] validate_chain+0x93a/0xd08
[ 204.830136] __lock_acquire+0x4ae/0x9d0
[ 204.830137] lock_acquire+0x114/0x280
[ 204.830140] __mutex_lock+0xa2/0x960
[ 204.830142] mutex_lock_nested+0x32/0x40
[ 204.830145] recover_store+0x4c/0xa8
[ 204.830147] kernfs_fop_write+0xe6/0x218
[ 204.830151] vfs_write+0xb0/0x1b8
[ 204.830152] ksys_write+0x6c/0xf8
[ 204.830154] system_call+0xd8/0x2d8
[ 204.830155]
-> #0 (kn->count#200){++++}:
[ 204.830187] check_noncircular+0x1e6/0x240
[ 204.830189] check_prev_add+0xfc/0xdb0
[ 204.830190] validate_chain+0x93a/0xd08
[ 204.830192] __lock_acquire+0x4ae/0x9d0
[ 204.830193] lock_acquire+0x114/0x280
[ 204.830194] __kernfs_remove.part.0+0x2e4/0x360
[ 204.830196] kernfs_remove_by_name_ns+0x5c/0xa8
[ 204.830198] remove_files.isra.0+0x4c/0x98
[ 204.830199] sysfs_remove_group+0x66/0xc8
[ 204.830201] sysfs_remove_groups+0x46/0x68
[ 204.830204] device_remove_attrs+0x52/0x90
[ 204.830207] device_del+0x182/0x418
[ 204.830208] pci_remove_bus_device+0x8a/0x130
[ 204.830210] pci_stop_and_remove_bus_device_locked+0x3a/0x48
[ 204.830212] disable_slot+0x68/0x100
[ 204.830213] power_write_file+0x7c/0x130
[ 204.830215] kernfs_fop_write+0xe6/0x218
[ 204.830217] vfs_write+0xb0/0x1b8
[ 204.830218] ksys_write+0x6c/0xf8
[ 204.830220] system_call+0xd8/0x2d8
[ 204.830221]
other info that might help us debug this:
[ 204.830223] Possible unsafe locking scenario:
[ 204.830224] CPU0 CPU1
[ 204.830225] ---- ----
[ 204.830226] lock(pci_rescan_remove_lock);
[ 204.830227] lock(kn->count#200);
[ 204.830229] lock(pci_rescan_remove_lock);
[ 204.830231] lock(kn->count#200);
[ 204.830233]
*** DEADLOCK ***
[ 204.830234] 4 locks held by bash/1034:
[ 204.830235] #0: 00000001b6fbc498 (sb_writers#4){.+.+}, at: vfs_write+0x158/0x1b8
[ 204.830239] #1: 000000018c9f5090 (&of->mutex){+.+.}, at: kernfs_fop_write+0xaa/0x218
[ 204.830242] #2: 00000001f7da0810 (kn->count#235){.+.+}, at: kernfs_fop_write+0xb6/0x218
[ 204.830245] #3: 00000000c16134a8 (pci_rescan_remove_lock){+.+.}, at: pci_stop_and_remove_bus_device_locked+0x26/0x48
[ 204.830248]
stack backtrace:
[ 204.830250] CPU: 2 PID: 1034 Comm: bash Tainted: G W 5.5.0-rc2-06072-gbc03ecc9a672 #6
[ 204.830252] Hardware name: IBM 8561 T01 703 (LPAR)
[ 204.830253] Call Trace:
[ 204.830257] [<00000000c05e10c0>] show_stack+0x88/0xf0
[ 204.830260] [<00000000c112dca4>] dump_stack+0xa4/0xe0
[ 204.830261] [<00000000c0694c06>] check_noncircular+0x1e6/0x240
[ 204.830263] [<00000000c0695bec>] check_prev_add+0xfc/0xdb0
[ 204.830264] [<00000000c06971da>] validate_chain+0x93a/0xd08
[ 204.830266] [<00000000c06994c6>] __lock_acquire+0x4ae/0x9d0
[ 204.830267] [<00000000c069867c>] lock_acquire+0x114/0x280
[ 204.830269] [<00000000c09ca15c>] __kernfs_remove.part.0+0x2e4/0x360
[ 204.830270] [<00000000c09cb5c4>] kernfs_remove_by_name_ns+0x5c/0xa8
[ 204.830272] [<00000000c09cee14>] remove_files.isra.0+0x4c/0x98
[ 204.830274] [<00000000c09cf2ae>] sysfs_remove_group+0x66/0xc8
[ 204.830276] [<00000000c09cf356>] sysfs_remove_groups+0x46/0x68
[ 204.830278] [<00000000c0e3dfe2>] device_remove_attrs+0x52/0x90
[ 204.830280] [<00000000c0e40382>] device_del+0x182/0x418
[ 204.830281] [<00000000c0dcfd7a>] pci_remove_bus_device+0x8a/0x130
[ 204.830283] [<00000000c0dcfe92>] pci_stop_and_remove_bus_device_locked+0x3a/0x48
[ 204.830285] [<00000000c0de7190>] disable_slot+0x68/0x100
[ 204.830286] [<00000000c0de6514>] power_write_file+0x7c/0x130
[ 204.830288] [<00000000c09cc846>] kernfs_fop_write+0xe6/0x218
[ 204.830290] [<00000000c08f3480>] vfs_write+0xb0/0x1b8
[ 204.830291] [<00000000c08f378c>] ksys_write+0x6c/0xf8
[ 204.830293] [<00000000c1154374>] system_call+0xd8/0x2d8
[ 204.830294] INFO: lockdep is turned off.
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Niklas Schnelle
Vasily Gorbik
parent
17cdec960c
commit
576c75e36c
@ -13,6 +13,8 @@
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#include <linux/stat.h>
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#include <linux/pci.h>
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#include "../../../drivers/pci/pci.h"
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#include <asm/sclp.h>
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#define zpci_attr(name, fmt, member) \
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@ -49,31 +51,50 @@ static DEVICE_ATTR_RO(mio_enabled);
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static ssize_t recover_store(struct device *dev, struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct kernfs_node *kn;
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struct pci_dev *pdev = to_pci_dev(dev);
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struct zpci_dev *zdev = to_zpci(pdev);
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int ret;
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int ret = 0;
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if (!device_remove_file_self(dev, attr))
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return count;
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/* Can't use device_remove_self() here as that would lead us to lock
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* the pci_rescan_remove_lock while holding the device' kernfs lock.
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* This would create a possible deadlock with disable_slot() which is
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* not directly protected by the device' kernfs lock but takes it
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* during the device removal which happens under
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* pci_rescan_remove_lock.
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*
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* This is analogous to sdev_store_delete() in
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* drivers/scsi/scsi_sysfs.c
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*/
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kn = sysfs_break_active_protection(&dev->kobj, &attr->attr);
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WARN_ON_ONCE(!kn);
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/* device_remove_file() serializes concurrent calls ignoring all but
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* the first
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*/
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device_remove_file(dev, attr);
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/* A concurrent call to recover_store() may slip between
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* sysfs_break_active_protection() and the sysfs file removal.
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* Once it unblocks from pci_lock_rescan_remove() the original pdev
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* will already be removed.
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*/
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pci_lock_rescan_remove();
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if (pci_dev_is_added(pdev)) {
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pci_stop_and_remove_bus_device(pdev);
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ret = zpci_disable_device(zdev);
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if (ret)
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goto error;
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goto out;
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ret = zpci_enable_device(zdev);
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if (ret)
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goto error;
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goto out;
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pci_rescan_bus(zdev->bus);
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}
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out:
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pci_unlock_rescan_remove();
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return count;
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error:
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pci_unlock_rescan_remove();
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return ret;
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if (kn)
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sysfs_unbreak_active_protection(kn);
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return ret ? ret : count;
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}
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static DEVICE_ATTR_WO(recover);
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