linux-kernel - [PATCH 1/1] thinkpad-acpi: kill hotkey_thread

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Message-ID: <20130307175359.GB15631@redhat.com>
Date:	Thu, 7 Mar 2013 18:53:59 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Mandeep Singh Baines <msb@...omium.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-acpi@...r.kernel.org, ibm-acpi@....eng.br,
	ibm-acpi-devel@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org, Aaron Lu <aaron.lu@...el.com>,
	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Artem Savkov <artem.savkov@...il.com>
Subject: [PATCH 1/1] thinkpad-acpi: kill hotkey_thread_mutex

hotkey_kthread() does try_to_freeze() under hotkey_thread_mutex.

We can simply kill this mutex, hotkey_poll_stop_sync() does not need
to serialize with hotkey_kthread(). When kthread_stop() returns the
thread is already dead, it called do_exit()->complete_vfork_done().

Reported-by: Artem Savkov <artem.savkov@...il.com>
Reported-by: Maciej Rutecki <maciej.rutecki@...il.com>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>

--- x/drivers/platform/x86/thinkpad_acpi.c
+++ x/drivers/platform/x86/thinkpad_acpi.c
@@ -1965,9 +1965,6 @@ struct tp_nvram_state {
 /* kthread for the hotkey poller */
 static struct task_struct *tpacpi_hotkey_task;
 
-/* Acquired while the poller kthread is running, use to sync start/stop */
-static struct mutex hotkey_thread_mutex;
-
 /*
  * Acquire mutex to write poller control variables as an
  * atomic block.
@@ -2463,8 +2460,6 @@ static int hotkey_kthread(void *data)
 	unsigned int poll_freq;
 	bool was_frozen;
 
-	mutex_lock(&hotkey_thread_mutex);
-
 	if (tpacpi_lifecycle == TPACPI_LIFE_EXITING)
 		goto exit;
 
@@ -2524,7 +2519,6 @@ static int hotkey_kthread(void *data)
 	}
 
 exit:
-	mutex_unlock(&hotkey_thread_mutex);
 	return 0;
 }
 
@@ -2534,9 +2528,6 @@ 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);
 	}
 }
 
@@ -3235,7 +3226,6 @@ static int __init hotkey_init(struct ibm
 	mutex_init(&hotkey_mutex);
 
 #ifdef CONFIG_THINKPAD_ACPI_HOTKEY_POLL
-	mutex_init(&hotkey_thread_mutex);
 	mutex_init(&hotkey_thread_data_mutex);
 #endif
 

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