mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-01-17 02:15:57 +00:00
c542ee1492
The delayed_bios list is protected by one mutex shared by all dm-delay devices. This mutex must be held whenever a bio is added or expired bios are removed from the list. Since a large number of expired bios could be on the list, flush_delayed_bios() can schedule while holding the mutex. This means a flush_delayed_bios() call on any dm-delay device can slow down delay_map() calls on any other dm-delay device. To keep dm-delay devices from slowing each other down and keep processing delay bios from slowing adding delayed bios, the global mutex has been removed, and each dm-delay device now has two locks. delayed_bios_lock is a spinlock that must be held whenever the delayed_bios list is accessed. process_bios_lock is a mutex that must be held whenever a process has temporarily pulled bios off the delayed_bios list to check which ones should be processed. It must be held until all the bios that won't be processed are returned to the list. This is what flush_delayed_bios() now does. The mutex is necessary to guarantee that delay_presuspend() sees the entire list of delayed bios when it calls flush_delayed_bios(). Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com> Signed-off-by: Mike Snitzer <snitzer@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 reStructuredText 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.