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markers: update preempt_disable. call_rcu, rcu_barrier comments 

Add comments requested by Andrew.

Updated comments about synchronize_sched().  Since we use call_rcu and
rcu_barrier now, these comments were out of sync with the code.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Mike Mason <mmlnx@us.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: David Smith <dsmith@redhat.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Adrian Bunk <adrian.bunk@movial.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mathieu Desnoyers 2008-03-24 12:29:47 -07:00 committed by Linus Torvalds
parent 5a982cbc7b
commit fd3c36f8b5
1 changed files with 8 additions and 11 deletions
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19
kernel/marker.c
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@ -104,9 +104,9 @@ void marker_probe_cb(const struct marker *mdata, void *call_private,
char ptype;
/*
* disabling preemption to make sure the teardown of the callbacks can
* be done correctly when they are in modules and they insure RCU read
* coherency.
* preempt_disable does two things : disabling preemption to make sure
* the teardown of the callbacks can be done correctly when they are in
* modules and they insure RCU read coherency.
*/
preempt_disable();
ptype = ACCESS_ONCE(mdata->ptype);
@ -551,9 +551,9 @@ static int set_marker(struct marker_entry **entry, struct marker *elem,
/*
* Disable a marker and its probe callback.
* Note: only after a synchronize_sched() issued after setting elem->call to the
* empty function insures that the original callback is not used anymore. This
* insured by preemption disabling around the call site.
* Note: only waiting an RCU period after setting elem->call to the empty
* function insures that the original callback is not used anymore. This insured
* by preempt_disable around the call site.
*/
static void disable_marker(struct marker *elem)
{
@ -565,8 +565,8 @@ static void disable_marker(struct marker *elem)
elem->ptype = 0; /* single probe */
/*
* Leave the private data and id there, because removal is racy and
* should be done only after a synchronize_sched(). These are never used
* until the next initialization anyway.
* should be done only after an RCU period. These are never used until
* the next initialization anyway.
*/
}
@ -601,9 +601,6 @@ void marker_update_probe_range(struct marker *begin,
/*
* Update probes, removing the faulty probes.
* Issues a synchronize_sched() when no reference to the module passed
* as parameter is found in the probes so the probe module can be
* safely unloaded from now on.
*
* Internal callback only changed before the first probe is connected to it.
* Single probe private data can only be changed on 0 -> 1 and 2 -> 1