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f27f949622
[ Upstream commit e16c7b07784f3fb03025939c4590b9a7c64970a7 ]
When analyzing a kernel waring message, Peter pointed out that there is a
race condition when the kworker is being frozen and falls into
try_to_freeze() with TASK_INTERRUPTIBLE, which could trigger a
might_sleep() warning in try_to_freeze(). Although the root cause is not
related to freeze()[1], it is still worthy to fix this issue ahead.
One possible race scenario:
CPU 0 CPU 1
----- -----
// kthread_worker_fn
set_current_state(TASK_INTERRUPTIBLE);
suspend_freeze_processes()
freeze_processes
static_branch_inc(&freezer_active);
freeze_kernel_threads
pm_nosig_freezing = true;
if (work) { //false
__set_current_state(TASK_RUNNING);
} else if (!freezing(current)) //false, been frozen
freezing():
if (static_branch_unlikely(&freezer_active))
if (pm_nosig_freezing)
return true;
schedule()
}
// state is still TASK_INTERRUPTIBLE
try_to_freeze()
might_sleep() <--- warning
Fix this by explicitly set the TASK_RUNNING before entering
try_to_freeze().
Link: https://lore.kernel.org/lkml/Zs2ZoAcUsZMX2B%2FI@chenyu5-mobl2/ [1]
Link: https://lkml.kernel.org/r/20240827112308.181081-1-yu.c.chen@intel.com
Fixes: b56c0d8937 ("kthread: implement kthread_worker")
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: David Gow <davidgow@google.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Mickaël Salaün <mic@digikod.net>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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.