linux-kernel - Re: [PATCH 0/4] cgroup: bug fixes for eventfd

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Date:	Sat, 2 Feb 2013 14:59:47 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	Tejun Heo <tj@...nel.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>,
	Davide Libenzi <davidel@...ilserver.org>,
	Aaron Durbin <adurbin@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH 0/4] cgroup: bug fixes for eventfd

(forgot to cc Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>, added)

On 2013/2/2 14:50, Li Zefan wrote:
> There're three bugs.
> 
> - If thread A is removing a cgroup, while thread B is closing an eventfd, the
> two threads might free the same cgroup event and thus crash the kernel.
> 
> This is fixed by patch #1 and patch #2.
> 
> - If there're multiple threads are blocking in read() on the same eventfd,
> and someone removes the cgroup, only one thread will be notified and unblocked,
> and others won't be unblocked until those threads are killed.
> 
> - If thread A is removing a cgroup, while thread B is registering a cgroup event
> and then read the eventfd, it might block until the thread is killed.
> 
> These two are fixed by patch #3.
> 
> 0001-eventfd-Introduce-eventfd_signal_hangup.patch
> 0002-cgroup-fix-cgroup_rmdir-vs-close-eventfd-race.patch
> 0003-eventfd-make-operations-on-eventfd-return-EIDRM-if-i.patch
> 0004-cgroup-adapt-to-the-new-way-of-detecting-cgroup-remo.patch
> 
> --
>  fs/eventfd.c                         | 30 ++++++++++++++++++++++++++++++
>  include/linux/eventfd.h              |  5 +++++
>  kernel/cgroup.c                      | 30 ++++++++++++++++++------------
>  tools/cgroup/cgroup_event_listener.c | 12 +++++-------
>  4 files changed, 58 insertions(+), 19 deletions(-)
> 

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