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Filename Latest commit message Latest commit date
Bart Van Assche b9c77583b0 nvme: avoid that deleting a controller triggers a circular locking complaint
Rework nvme_delete_ctrl_sync() such that it does not have to wait for
queued work. This patch avoids that test nvme/008 triggers the following
complaint:

WARNING: possible circular locking dependency detected
5.0.0-rc6-dbg+ #10 Not tainted
------------------------------------------------------
nvme/7918 is trying to acquire lock:
000000009a1a7b69 ((work_completion)(&ctrl->delete_work)){+.+.}, at: __flush_work+0x379/0x410

but task is already holding lock:
00000000ef5a45b4 (kn->count#389){++++}, at: kernfs_remove_self+0x196/0x210

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (kn->count#389){++++}:
       lock_acquire+0xc5/0x1e0
       __kernfs_remove+0x42a/0x4a0
       kernfs_remove_by_name_ns+0x45/0x90
       remove_files.isra.1+0x3a/0x90
       sysfs_remove_group+0x5c/0xc0
       sysfs_remove_groups+0x39/0x60
       device_remove_attrs+0x68/0xb0
       device_del+0x24d/0x570
       cdev_device_del+0x1a/0x50
       nvme_delete_ctrl_work+0xbd/0xe0
       process_one_work+0x4f1/0xa40
       worker_thread+0x67/0x5b0
       kthread+0x1cf/0x1f0
       ret_from_fork+0x24/0x30

-> #0 ((work_completion)(&ctrl->delete_work)){+.+.}:
       __lock_acquire+0x1323/0x17b0
       lock_acquire+0xc5/0x1e0
       __flush_work+0x399/0x410
       flush_work+0x10/0x20
       nvme_delete_ctrl_sync+0x65/0x70
       nvme_sysfs_delete+0x4f/0x60
       dev_attr_store+0x3e/0x50
       sysfs_kf_write+0x87/0xa0
       kernfs_fop_write+0x186/0x240
       __vfs_write+0xd7/0x430
       vfs_write+0xfa/0x260
       ksys_write+0xab/0x130
       __x64_sys_write+0x43/0x50
       do_syscall_64+0x71/0x210
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(kn->count#389);
                               lock((work_completion)(&ctrl->delete_work));
                               lock(kn->count#389);
  lock((work_completion)(&ctrl->delete_work));

 *** DEADLOCK ***

3 locks held by nvme/7918:
 #0: 00000000e2223b44 (sb_writers#6){.+.+}, at: vfs_write+0x1eb/0x260
 #1: 000000003404976f (&of->mutex){+.+.}, at: kernfs_fop_write+0x128/0x240
 #2: 00000000ef5a45b4 (kn->count#389){++++}, at: kernfs_remove_self+0x196/0x210

stack backtrace:
CPU: 4 PID: 7918 Comm: nvme Not tainted 5.0.0-rc6-dbg+ #10
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
Call Trace:
 dump_stack+0x86/0xca
 print_circular_bug.isra.36.cold.54+0x173/0x1d5
 check_prev_add.constprop.45+0x996/0x1110
 __lock_acquire+0x1323/0x17b0
 lock_acquire+0xc5/0x1e0
 __flush_work+0x399/0x410
 flush_work+0x10/0x20
 nvme_delete_ctrl_sync+0x65/0x70
 nvme_sysfs_delete+0x4f/0x60
 dev_attr_store+0x3e/0x50
 sysfs_kf_write+0x87/0xa0
 kernfs_fop_write+0x186/0x240
 __vfs_write+0xd7/0x430
 vfs_write+0xfa/0x260
 ksys_write+0xab/0x130
 __x64_sys_write+0x43/0x50
 do_syscall_64+0x71/0x210
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2019-02-20 07:19:42 -07:00
arch Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-10 09:57:42 -08:00
block block: avoid to READ fields of null bio 2019-02-19 09:19:06 -07:00
certs
crypto
Documentation Linux 5.0-rc6 2019-02-15 08:43:59 -07:00
drivers nvme: avoid that deleting a controller triggers a circular locking complaint 2019-02-20 07:19:42 -07:00
firmware
fs Linux 5.0-rc6 2019-02-15 08:43:59 -07:00
include Linux 5.0-rc6 2019-02-15 08:43:59 -07:00
init psi: clarify the Kconfig text for the default-disable option 2019-02-01 15:46:24 -08:00
ipc
kernel Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-10 09:48:18 -08:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-08 11:21:54 -08:00
LICENSES
mm mm: migrate: don't rely on __PageMovable() of newpage after unlocking it 2019-02-01 15:46:24 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-08 11:21:54 -08:00
samples samples: mei: use /dev/mei0 instead of /dev/mei 2019-01-30 15:24:45 +01:00
scripts Bug fixes for gcc-plugins 2019-01-21 13:07:03 +13:00
security apparmor: Fix aa_label_build() error handling for failed merges 2019-02-01 08:01:39 -08:00
sound sound fixes for 5.0-rc6 2019-02-07 08:33:56 +00:00
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-10 09:48:18 -08:00
usr
virt kvm: fix kvm_ioctl_create_device() reference counting (CVE-2019-6974) 2019-02-07 19:02:38 +01:00
.clang-format clang-format: Update .clang-format with the latest for_each macro list 2019-01-19 19:26:06 +01:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2019-02-09 13:43:12 -08:00
Makefile Linux 5.0-rc6 2019-02-10 14:42:20 -08:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.