The patch titled markers: fix markers read barrier for multiple probes has been removed from the -mm tree. Its filename was markers-fix-markers-read-barrier-for-multiple-probes.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: markers: fix markers read barrier for multiple probes From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> Paul pointed out two incorrect read barriers in the marker handler code in the path where multiple probes are connected. Those are ordering reads of "ptype" (single or multi probe marker), "multi" array pointer, and "multi" array data access. It should be ordered like this : read ptype smp_rmb() read multi array pointer smp_read_barrier_depends() access data referenced by multi array pointer The code with a single probe connected (optimized case, does not have to allocate an array) has correct memory ordering. It applies to kernel 2.6.26.x, 2.6.25.x and linux-next. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxx> [2.6.25.x, 2.6.26.x] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/marker.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff -puN kernel/marker.c~markers-fix-markers-read-barrier-for-multiple-probes kernel/marker.c --- a/kernel/marker.c~markers-fix-markers-read-barrier-for-multiple-probes +++ a/kernel/marker.c @@ -126,6 +126,11 @@ void marker_probe_cb(const struct marker struct marker_probe_closure *multi; int i; /* + * Read mdata->ptype before mdata->multi. + */ + smp_rmb(); + multi = mdata->multi; + /* * multi points to an array, therefore accessing the array * depends on reading multi. However, even in this case, * we must insure that the pointer is read _before_ the array @@ -133,7 +138,6 @@ void marker_probe_cb(const struct marker * in the fast path, so put the explicit barrier here. */ smp_read_barrier_depends(); - multi = mdata->multi; for (i = 0; multi[i].func; i++) { va_start(args, call_private); multi[i].func(multi[i].probe_private, call_private, @@ -175,6 +179,11 @@ void marker_probe_cb_noarg(const struct struct marker_probe_closure *multi; int i; /* + * Read mdata->ptype before mdata->multi. + */ + smp_rmb(); + multi = mdata->multi; + /* * multi points to an array, therefore accessing the array * depends on reading multi. However, even in this case, * we must insure that the pointer is read _before_ the array @@ -182,7 +191,6 @@ void marker_probe_cb_noarg(const struct * in the fast path, so put the explicit barrier here. */ smp_read_barrier_depends(); - multi = mdata->multi; for (i = 0; multi[i].func; i++) multi[i].func(multi[i].probe_private, call_private, mdata->format, &args); _ Patches currently in -mm which might be from mathieu.desnoyers@xxxxxxxxxx are origin.patch linux-next.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html