linux-kernel - [PATCH] markers: comment usage of marker_synchronize

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Date:	Wed, 26 Nov 2008 20:36:52 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Avi Kivity <avi@...hat.com>,
	kvm@...r.kernel.org, Lai Jiangshan <laijs@...fujitsu.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>
Subject: [PATCH] markers: comment usage of marker_synchronize_unregister()

Add more comments to marker_synchronize_unregister() in order to
reduce the chance of misusing.

Based on comments from Lai Jiangshan <laijs@...fujitsu.com>.

Cc: Lai Jiangshan <laijs@...fujitsu.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Signed-off-by: Wu Fengguang <wfg@...ux.intel.com>
---

I'm still not sure about the last sentence. Can anyone clarify on
this? Thanks!

diff --git a/include/linux/marker.h b/include/linux/marker.h
index 889196c..89ce1b8 100644
--- a/include/linux/marker.h
+++ b/include/linux/marker.h
@@ -164,6 +164,12 @@ extern void *marker_get_private_data(const char *name, marker_probe_func *probe,
  * marker_synchronize_unregister must be called between the last marker probe
  * unregistration and the end of module exit to make sure there is no caller
  * executing a probe when it is freed.
+ *
+ * It must be called _also_ between unregistration and destruction the data
+ * that unregistration-ed probes need to make sure there is no caller executing
+ * a probe when it's data is destroyed.
+ *
+ * It works reliably only when all probe routines do not sleep and reschedule.
  */
 #define marker_synchronize_unregister() synchronize_sched()
 
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