If ->safemode == 1, md_check_recovery() will try to get the mddev lock
and perform various other checks.
If mddev->in_sync is zero, it will call set_in_sync, and clear
->safemode. However if mddev->in_sync is not zero, ->safemode will not
be cleared.
When md_check_recovery() drops the mddev lock, the thread is woken
up again. Normally it would just check if there was anything else to
do, find nothing, and go to sleep. However as ->safemode was not
cleared, it will take the mddev lock again, then wake itself up
when unlocking.
This results in an infinite loop, repeatedly calling
md_check_recovery(), which RCU or the soft-lockup detector
will eventually complain about.
Prior to commit 4ad23a9764 ("MD: use per-cpu counter for
writes_pending"), safemode would only be set to one when the
writes_pending counter reached zero, and would be cleared again
when writes_pending is incremented. Since that patch, safemode
is set more freely, but is not reliably cleared.
So in md_check_recovery() clear ->safemode before checking ->in_sync.
Fixes: 4ad23a9764 ("MD: use per-cpu counter for writes_pending")
Cc: stable@vger.kernel.org (4.12+)
Reported-by: Dominik Brodowski <linux@dominikbrodowski.net>
Reported-by: David R <david@unsolicited.net>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Linux kernel
============
This file was moved to Documentation/admin-guide/README.rst
Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
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.
33182d15c6