From 28325df0d9339b7f3aba9c45174d4586223ef46b Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Fri, 25 Jul 2008 01:48:38 -0700 Subject: markers: use rcu_barrier_sched() and call_rcu_sched() rcu_barrier_sched() and call_rcu_sched() were introduced in 2.6.26 for the Markers. Change the marker code to use them. It can be seen as a fix since the marker code was using an ugly, temporary, #ifdef hack to work around CONFIG_PREEMPT_RCU. Signed-off-by: Mathieu Desnoyers Acked-by: Paul McKenney Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/marker.c | 25 ++++++++----------------- 1 file changed, 8 insertions(+), 17 deletions(-) (limited to 'kernel/marker.c') diff --git a/kernel/marker.c b/kernel/marker.c index 1abfb923b76..971da531790 100644 --- a/kernel/marker.c +++ b/kernel/marker.c @@ -441,7 +441,7 @@ static int remove_marker(const char *name) hlist_del(&e->hlist); /* Make sure the call_rcu has been executed */ if (e->rcu_pending) - rcu_barrier(); + rcu_barrier_sched(); kfree(e); return 0; } @@ -476,7 +476,7 @@ static int marker_set_format(struct marker_entry **entry, const char *format) hlist_del(&(*entry)->hlist); /* Make sure the call_rcu has been executed */ if ((*entry)->rcu_pending) - rcu_barrier(); + rcu_barrier_sched(); kfree(*entry); *entry = e; trace_mark(core_marker_format, "name %s format %s", @@ -655,7 +655,7 @@ int marker_probe_register(const char *name, const char *format, * make sure it's executed now. */ if (entry->rcu_pending) - rcu_barrier(); + rcu_barrier_sched(); old = marker_entry_add_probe(entry, probe, probe_private); if (IS_ERR(old)) { ret = PTR_ERR(old); @@ -670,10 +670,7 @@ int marker_probe_register(const char *name, const char *format, entry->rcu_pending = 1; /* write rcu_pending before calling the RCU callback */ smp_wmb(); -#ifdef CONFIG_PREEMPT_RCU - synchronize_sched(); /* Until we have the call_rcu_sched() */ -#endif - call_rcu(&entry->rcu, free_old_closure); + call_rcu_sched(&entry->rcu, free_old_closure); end: mutex_unlock(&markers_mutex); return ret; @@ -704,7 +701,7 @@ int marker_probe_unregister(const char *name, if (!entry) goto end; if (entry->rcu_pending) - rcu_barrier(); + rcu_barrier_sched(); old = marker_entry_remove_probe(entry, probe, probe_private); mutex_unlock(&markers_mutex); marker_update_probes(); /* may update entry */ @@ -716,10 +713,7 @@ int marker_probe_unregister(const char *name, entry->rcu_pending = 1; /* write rcu_pending before calling the RCU callback */ smp_wmb(); -#ifdef CONFIG_PREEMPT_RCU - synchronize_sched(); /* Until we have the call_rcu_sched() */ -#endif - call_rcu(&entry->rcu, free_old_closure); + call_rcu_sched(&entry->rcu, free_old_closure); remove_marker(name); /* Ignore busy error message */ ret = 0; end: @@ -786,7 +780,7 @@ int marker_probe_unregister_private_data(marker_probe_func *probe, goto end; } if (entry->rcu_pending) - rcu_barrier(); + rcu_barrier_sched(); old = marker_entry_remove_probe(entry, NULL, probe_private); mutex_unlock(&markers_mutex); marker_update_probes(); /* may update entry */ @@ -797,10 +791,7 @@ int marker_probe_unregister_private_data(marker_probe_func *probe, entry->rcu_pending = 1; /* write rcu_pending before calling the RCU callback */ smp_wmb(); -#ifdef CONFIG_PREEMPT_RCU - synchronize_sched(); /* Until we have the call_rcu_sched() */ -#endif - call_rcu(&entry->rcu, free_old_closure); + call_rcu_sched(&entry->rcu, free_old_closure); remove_marker(entry->name); /* Ignore busy error message */ end: mutex_unlock(&markers_mutex); -- cgit v1.2.3-70-g09d2 From 5def9a3a22e09c99717f41ab7f07ec9e1a1f3ec8 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Tue, 29 Jul 2008 22:33:31 -0700 Subject: markers: fix markers read barrier for multiple probes 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 Cc: "Paul E. McKenney" Cc: [2.6.25.x, 2.6.26.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/marker.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'kernel/marker.c') diff --git a/kernel/marker.c b/kernel/marker.c index 971da531790..7d1faecd7a5 100644 --- a/kernel/marker.c +++ b/kernel/marker.c @@ -125,6 +125,11 @@ void marker_probe_cb(const struct marker *mdata, void *call_private, ...) } else { 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, @@ -133,7 +138,6 @@ void marker_probe_cb(const struct marker *mdata, void *call_private, ...) * 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, @@ -174,6 +178,11 @@ void marker_probe_cb_noarg(const struct marker *mdata, void *call_private, ...) } else { 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, @@ -182,7 +191,6 @@ void marker_probe_cb_noarg(const struct marker *mdata, void *call_private, ...) * 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); -- cgit v1.2.3-70-g09d2