aa39cc6757
GC task can deadlock in read_cache_page() because it may attempt to release a page that is actually allocated by another task in jffs2_write_begin(). The reason is that in jffs2_write_begin() there is a small window a cache page is allocated for use but not set Uptodate yet. This ends up with a deadlock between two tasks: 1) A task (e.g. file copy) - jffs2_write_begin() locks a cache page - jffs2_write_end() tries to lock "alloc_sem" from jffs2_reserve_space() <-- STUCK 2) GC task (jffs2_gcd_mtd3) - jffs2_garbage_collect_pass() locks "alloc_sem" - try to lock the same cache page in read_cache_page() <-- STUCK So to avoid this deadlock, hold "alloc_sem" in jffs2_write_begin() while reading data in a cache page. Signed-off-by: Kyeong Yoo <kyeong.yoo@alliedtelesis.co.nz> Signed-off-by: Richard Weinberger <richard@nod.at>
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.