Messages in this thread Patch in this message | | | Date | Wed, 19 Mar 2008 20:27:39 -0400 | From | Mathieu Desnoyers <> | Subject | [patch 2/4] Markers - Update preempt_disable. call_rcu, rcu_barrier comments. |
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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: Andrew Morton <akpm@osdl.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> --- kernel/marker.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-)
Index: linux-2.6-lttng/kernel/marker.c =================================================================== --- linux-2.6-lttng.orig/kernel/marker.c 2008-03-19 18:26:47.000000000 -0400 +++ linux-2.6-lttng/kernel/marker.c 2008-03-19 18:30:26.000000000 -0400 @@ -104,9 +104,9 @@ void marker_probe_cb(const struct marker 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_entr /* * 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->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 ma /* * 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 -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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