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Filename Latest commit message Latest commit date
Tetsuo Handa 04aa8187eb workqueue: don't skip lockdep work dependency in cancel_work_sync() 
[ Upstream commit c0feea594e058223973db94c1c32a830c9807c86 ]

Like Hillf Danton mentioned

  syzbot should have been able to catch cancel_work_sync() in work context
  by checking lockdep_map in __flush_work() for both flush and cancel.

in [1], being unable to report an obvious deadlock scenario shown below is
broken. From locking dependency perspective, sync version of cancel request
should behave as if flush request, for it waits for completion of work if
that work has already started execution.

  ----------
  #include <linux/module.h>
  #include <linux/sched.h>
  static DEFINE_MUTEX(mutex);
  static void work_fn(struct work_struct *work)
  {
    schedule_timeout_uninterruptible(HZ / 5);
    mutex_lock(&mutex);
    mutex_unlock(&mutex);
  }
  static DECLARE_WORK(work, work_fn);
  static int __init test_init(void)
  {
    schedule_work(&work);
    schedule_timeout_uninterruptible(HZ / 10);
    mutex_lock(&mutex);
    cancel_work_sync(&work);
    mutex_unlock(&mutex);
    return -EINVAL;
  }
  module_init(test_init);
  MODULE_LICENSE("GPL");
  ----------

The check this patch restores was added by commit 0976dfc1d0
("workqueue: Catch more locking problems with flush_work()").

Then, lockdep's crossrelease feature was added by commit b09be676e0
("locking/lockdep: Implement the 'crossrelease' feature"). As a result,
this check was once removed by commit fd1a5b04df ("workqueue: Remove
now redundant lock acquisitions wrt. workqueue flushes").

But lockdep's crossrelease feature was removed by commit e966eaeeb6
("locking/lockdep: Remove the cross-release locking checks"). At this
point, this check should have been restored.

Then, commit d6e89786be ("workqueue: skip lockdep wq dependency in
cancel_work_sync()") introduced a boolean flag in order to distinguish
flush_work() and cancel_work_sync(), for checking "struct workqueue_struct"
dependency when called from cancel_work_sync() was causing false positives.

Then, commit 87915adc3f ("workqueue: re-add lockdep dependencies for
flushing") tried to restore "struct work_struct" dependency check, but by
error checked this boolean flag. Like an example shown above indicates,
"struct work_struct" dependency needs to be checked for both flush_work()
and cancel_work_sync().

Link: https://lkml.kernel.org/r/20220504044800.4966-1-hdanton@sina.com [1]
Reported-by: Hillf Danton <hdanton@sina.com>
Suggested-by: Lai Jiangshan <jiangshanlai@gmail.com>
Fixes: 87915adc3f ("workqueue: re-add lockdep dependencies for flushing")
Cc: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-09-28 11:04:09 +02:00
arch MIPS: Loongson32: Fix PHY-mode being left unspecified 2022-09-28 11:04:06 +02:00
block
certs
crypto
Documentation Input: iforce - add support for Boeder Force Feedback Wheel 2022-09-20 12:27:59 +02:00
drivers drm/rockchip: Fix return type of cdn_dp_connector_mode_valid 2022-09-28 11:04:09 +02:00
fs cifs: always initialize struct msghdr smb_msg completely 2022-09-28 11:04:08 +02:00
include serial: Create uart_xmit_advance() 2022-09-28 11:04:08 +02:00
init
ipc
kernel workqueue: don't skip lockdep work dependency in cancel_work_sync() 2022-09-28 11:04:09 +02:00
lib lib/vdso: Mark do_hres() and do_coarse() as __always_inline 2022-09-05 10:27:47 +02:00
LICENSES
mm mm/slub: fix to return errno if kmalloc() fails 2022-09-28 11:04:04 +02:00
net net: sched: fix possible refcount leak in tc_new_tfilter() 2022-09-28 11:04:07 +02:00
samples
scripts mksysmap: Fix the mismatch of 'L0' symbols in System.map 2022-09-28 11:03:59 +02:00
security apparmor: Fix memleak in aa_simple_write_to_buffer() 2022-08-25 11:18:21 +02:00
sound ALSA: hda/realtek: Enable 4-speaker output Dell Precision 5530 laptop 2022-09-28 11:04:04 +02:00
tools perf kcore_copy: Do not check /proc/modules is unchanged 2022-09-28 11:04:07 +02:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: add Chandan as xfs maintainer for 5.4.y 2022-09-28 11:03:58 +02:00
Makefile Linux 5.4.214 2022-09-20 12:28:00 +02:00
README

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.