Messages in this thread | | | Date | Wed, 6 Mar 2013 16:44:20 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] thinkpad-acpi: fix potential suspend blocking issue |
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On 03/05, Henrique de Moraes Holschuh wrote: > > On Tue, 05 Mar 2013, Mandeep Singh Baines wrote: > > This mutex seems wrong. Its held the entire time the kthread is > > running. I think its used to synchronize on the exit of the kthread. A > > completion would more appropriate in that case. > > From the top of the driver source: > > /* Acquired while the poller kthread is running, use to sync start/stop */ > static struct mutex hotkey_thread_mutex;
I simply can't understand what this "sync start/stop" means...
Ignoring hotkey_kthread(), the only user is
static void hotkey_poll_stop_sync(void) { if (tpacpi_hotkey_task) { kthread_stop(tpacpi_hotkey_task); tpacpi_hotkey_task = NULL; mutex_lock(&hotkey_thread_mutex); /* at this point, the thread did exit */ mutex_unlock(&hotkey_thread_mutex); } }
And I simply do not understand the comment. This thread has already exited when kthread_stop() returns (OK, it can be running do_exit() paths but this doesn't matter). So this mutex_lock() buys nothing afaics.
As for serializing with hotkey_poll_setup/etc, looks like this code relies on hotkey_mutex.
So I think hotkey_thread_mutex can be simply removed?
Oleg.
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