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    Subject[patch 3/4] Markers - Remove ACCESS_ONCE
    As Paul pointed out, the ACCESS_ONCE are not needed because we already have the
    explicit surrounding memory barriers.

    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 | 12 ++++++------
    1 file changed, 6 insertions(+), 6 deletions(-)

    Index: linux-2.6-lttng/kernel/marker.c
    ===================================================================
    --- linux-2.6-lttng.orig/kernel/marker.c 2008-03-19 18:30:26.000000000 -0400
    +++ linux-2.6-lttng/kernel/marker.c 2008-03-19 18:32:16.000000000 -0400
    @@ -109,13 +109,13 @@ void marker_probe_cb(const struct marker
    * modules and they insure RCU read coherency.
    */
    preempt_disable();
    - ptype = ACCESS_ONCE(mdata->ptype);
    + ptype = mdata->ptype;
    if (likely(!ptype)) {
    marker_probe_func *func;
    /* Must read the ptype before ptr. They are not data dependant,
    * so we put an explicit smp_rmb() here. */
    smp_rmb();
    - func = ACCESS_ONCE(mdata->single.func);
    + func = mdata->single.func;
    /* Must read the ptr before private data. They are not data
    * dependant, so we put an explicit smp_rmb() here. */
    smp_rmb();
    @@ -133,7 +133,7 @@ void marker_probe_cb(const struct marker
    * in the fast path, so put the explicit barrier here.
    */
    smp_read_barrier_depends();
    - multi = ACCESS_ONCE(mdata->multi);
    + multi = mdata->multi;
    for (i = 0; multi[i].func; i++) {
    va_start(args, fmt);
    multi[i].func(multi[i].probe_private, call_private, fmt,
    @@ -161,13 +161,13 @@ void marker_probe_cb_noarg(const struct
    char ptype;

    preempt_disable();
    - ptype = ACCESS_ONCE(mdata->ptype);
    + ptype = mdata->ptype;
    if (likely(!ptype)) {
    marker_probe_func *func;
    /* Must read the ptype before ptr. They are not data dependant,
    * so we put an explicit smp_rmb() here. */
    smp_rmb();
    - func = ACCESS_ONCE(mdata->single.func);
    + func = mdata->single.func;
    /* Must read the ptr before private data. They are not data
    * dependant, so we put an explicit smp_rmb() here. */
    smp_rmb();
    @@ -183,7 +183,7 @@ void marker_probe_cb_noarg(const struct
    * in the fast path, so put the explicit barrier here.
    */
    smp_read_barrier_depends();
    - multi = ACCESS_ONCE(mdata->multi);
    + multi = mdata->multi;
    for (i = 0; multi[i].func; i++)
    multi[i].func(multi[i].probe_private, call_private, fmt,
    &args);
    --
    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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