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[ Upstream commit 018d26fcd12a75fb9b5fe233762aa3f2f0854b88 ] In our production environment we have faced with problem that updating classid in cgroup with heavy tasks cause long freeze of the file tables in this tasks. By heavy tasks we understand tasks with many threads and opened sockets (e.g. balancers). This freeze leads to an increase number of client timeouts. This patch implements following logic to fix this issue: аfter iterating 1000 file descriptors file table lock will be released thus providing a time gap for socket creation/deletion. Now update is non atomic and socket may be skipped using calls: dup2(oldfd, newfd); close(oldfd); But this case is not typical. Moreover before this patch skip is possible too by hiding socket fd in unix socket buffer. New sockets will be allocated with updated classid because cgroup state is updated before start of the file descriptors iteration. So in common cases this patch has no side effects. Signed-off-by: Dmitry Yakunin <zeil@yandex-team.ru> Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.