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authorPetr Mladek <pmladek@suse.com>2016-10-11 22:55:36 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-12 00:06:33 +0200
commit8197b3d43b250b8214b9913878e9227eef8bd85f (patch)
tree60dbc6fc294f84654190fdbfc329b328a4261126 /arch/mips/paravirt
parentkthread: add kthread_destroy_worker() (diff)
downloadlinux-8197b3d43b250b8214b9913878e9227eef8bd85f.tar.xz
linux-8197b3d43b250b8214b9913878e9227eef8bd85f.zip
kthread: detect when a kthread work is used by more workers
Nothing currently prevents a work from queuing for a kthread worker when it is already running on another one. This means that the work might run in parallel on more than one worker. Also some operations are not reliable, e.g. flush. This problem will be even more visible after we add kthread_cancel_work() function. It will only have "work" as the parameter and will use worker->lock to synchronize with others. Well, normally this is not a problem because the API users are sane. But bugs might happen and users also might be crazy. This patch adds a warning when we try to insert the work for another worker. It does not fully prevent the misuse because it would make the code much more complicated without a big benefit. It adds the same warning also into kthread_flush_work() instead of the repeated attempts to get the right lock. A side effect is that one needs to explicitly reinitialize the work if it must be queued into another worker. This is needed, for example, when the worker is stopped and started again. It is a bit inconvenient. But it looks like a good compromise between the stability and complexity. I have double checked all existing users of the kthread worker API and they all seems to initialize the work after the worker gets started. Just for completeness, the patch adds a check that the work is not already in a queue. The patch also puts all the checks into a separate function. It will be reused when implementing delayed works. Link: http://lkml.kernel.org/r/1470754545-17632-8-git-send-email-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Borislav Petkov <bp@suse.de> Cc: Michal Hocko <mhocko@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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