lkml.org 
[lkml]   [2020]   [Feb]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH AUTOSEL 5.5 094/542] s390/pci: Fix possible deadlock in recover_store()
    Date
    From: Niklas Schnelle <schnelle@linux.ibm.com>

    [ Upstream commit 576c75e36c689bec6a940e807bae27291ab0c0de ]

    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 0ee223b2e1f6 ("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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/s390/pci/pci_sysfs.c | 63 ++++++++++++++++++++++++++-------------
    1 file changed, 42 insertions(+), 21 deletions(-)

    diff --git a/arch/s390/pci/pci_sysfs.c b/arch/s390/pci/pci_sysfs.c
    index a433ba01a3175..215f17437a4f6 100644
    --- a/arch/s390/pci/pci_sysfs.c
    +++ b/arch/s390/pci/pci_sysfs.c
    @@ -13,6 +13,8 @@
    #include <linux/stat.h>
    #include <linux/pci.h>

    +#include "../../../drivers/pci/pci.h"
    +
    #include <asm/sclp.h>

    #define zpci_attr(name, fmt, member) \
    @@ -49,31 +51,50 @@ static DEVICE_ATTR_RO(mio_enabled);
    static ssize_t recover_store(struct device *dev, struct device_attribute *attr,
    const char *buf, size_t count)
    {
    + struct kernfs_node *kn;
    struct pci_dev *pdev = to_pci_dev(dev);
    struct zpci_dev *zdev = to_zpci(pdev);
    - int ret;
    -
    - if (!device_remove_file_self(dev, attr))
    - return count;
    -
    + int ret = 0;
    +
    + /* Can't use device_remove_self() here as that would lead us to lock
    + * the pci_rescan_remove_lock while holding the device' kernfs lock.
    + * This would create a possible deadlock with disable_slot() which is
    + * not directly protected by the device' kernfs lock but takes it
    + * during the device removal which happens under
    + * pci_rescan_remove_lock.
    + *
    + * This is analogous to sdev_store_delete() in
    + * drivers/scsi/scsi_sysfs.c
    + */
    + kn = sysfs_break_active_protection(&dev->kobj, &attr->attr);
    + WARN_ON_ONCE(!kn);
    + /* device_remove_file() serializes concurrent calls ignoring all but
    + * the first
    + */
    + device_remove_file(dev, attr);
    +
    + /* A concurrent call to recover_store() may slip between
    + * sysfs_break_active_protection() and the sysfs file removal.
    + * Once it unblocks from pci_lock_rescan_remove() the original pdev
    + * will already be removed.
    + */
    pci_lock_rescan_remove();
    - pci_stop_and_remove_bus_device(pdev);
    - ret = zpci_disable_device(zdev);
    - if (ret)
    - goto error;
    -
    - ret = zpci_enable_device(zdev);
    - if (ret)
    - goto error;
    -
    - pci_rescan_bus(zdev->bus);
    + if (pci_dev_is_added(pdev)) {
    + pci_stop_and_remove_bus_device(pdev);
    + ret = zpci_disable_device(zdev);
    + if (ret)
    + goto out;
    +
    + ret = zpci_enable_device(zdev);
    + if (ret)
    + goto out;
    + pci_rescan_bus(zdev->bus);
    + }
    +out:
    pci_unlock_rescan_remove();
    -
    - return count;
    -
    -error:
    - pci_unlock_rescan_remove();
    - return ret;
    + if (kn)
    + sysfs_unbreak_active_protection(kn);
    + return ret ? ret : count;
    }
    static DEVICE_ATTR_WO(recover);

    --
    2.20.1
    \
     
     \ /
      Last update: 2020-02-14 19:18    [W:2.172 / U:2.788 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site