* [patch 1/2] tracepoint: simplify for tracepoint using RCU
2008-10-31 0:26 [patch 0/2] Tracepoint updates for -tip mathieu.desnoyers
@ 2008-10-31 0:27 ` mathieu.desnoyers
2008-10-31 0:27 ` [patch 2/2] tracepoint: introduce *_noupdate APIs. (v2) mathieu.desnoyers
1 sibling, 0 replies; 3+ messages in thread
From: mathieu.desnoyers @ 2008-10-31 0:27 UTC (permalink / raw)
To: Ingo Molnar, linux-kernel; +Cc: Lai Jiangshan, Mathieu Desnoyers
[-- Attachment #1: tracepoint-simplify-for-tracepoint-using-rcu.patch --]
[-- Type: text/plain, Size: 7129 bytes --]
Now, unused memory is handled by struct tp_probes.
old code use these three field to handle unused memory.
struct tracepoint_entry {
...
struct rcu_head rcu;
void *oldptr;
unsigned char rcu_pending:1;
...
};
in this way, unused memory is handled by struct tracepoint_entry.
it bring reenter bug(it was fixed) and tracepoint.c is filled
full of ".*rcu.*" code statements. this patch remove all these.
and:
rcu_barrier_sched() is removed.
Do not need regain tracepoints_mutex after tracepoint_update_probes()
several little cleanup.
Mathieu Desnoyers :
Update patch to make sure it applies correctly on top of
tracepoint-check-if-the-probe-has-been-registered.patch
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
kernel/tracepoint.c | 111 +++++++++++++++++-----------------------------------
1 file changed, 37 insertions(+), 74 deletions(-)
Index: linux-2.6-lttng/kernel/tracepoint.c
===================================================================
--- linux-2.6-lttng.orig/kernel/tracepoint.c 2008-10-30 20:12:13.000000000 -0400
+++ linux-2.6-lttng/kernel/tracepoint.c 2008-10-30 20:17:25.000000000 -0400
@@ -43,6 +43,7 @@ static DEFINE_MUTEX(tracepoints_mutex);
*/
#define TRACEPOINT_HASH_BITS 6
#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
+static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
/*
* Note about RCU :
@@ -54,40 +55,40 @@ struct tracepoint_entry {
struct hlist_node hlist;
void **funcs;
int refcount; /* Number of times armed. 0 if disarmed. */
- struct rcu_head rcu;
- void *oldptr;
- unsigned char rcu_pending:1;
char name[0];
};
-static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
+struct tp_probes {
+ struct rcu_head rcu;
+ void *probes[0];
+};
-static void free_old_closure(struct rcu_head *head)
+static inline void *allocate_probes(int count)
{
- struct tracepoint_entry *entry = container_of(head,
- struct tracepoint_entry, rcu);
- kfree(entry->oldptr);
- /* Make sure we free the data before setting the pending flag to 0 */
- smp_wmb();
- entry->rcu_pending = 0;
+ struct tp_probes *p = kmalloc(count * sizeof(void *)
+ + sizeof(struct tp_probes), GFP_KERNEL);
+ return p == NULL ? NULL : p->probes;
}
-static void tracepoint_entry_free_old(struct tracepoint_entry *entry, void *old)
+static void rcu_free_old_probes(struct rcu_head *head)
{
- if (!old)
- return;
- entry->oldptr = old;
- entry->rcu_pending = 1;
- /* write rcu_pending before calling the RCU callback */
- smp_wmb();
- call_rcu_sched(&entry->rcu, free_old_closure);
+ kfree(container_of(head, struct tp_probes, rcu));
+}
+
+static inline void release_probes(void *old)
+{
+ if (old) {
+ struct tp_probes *tp_probes = container_of(old,
+ struct tp_probes, probes[0]);
+ call_rcu(&tp_probes->rcu, rcu_free_old_probes);
+ }
}
static void debug_print_probes(struct tracepoint_entry *entry)
{
int i;
- if (!tracepoint_debug)
+ if (!tracepoint_debug || !entry->funcs)
return;
for (i = 0; entry->funcs[i]; i++)
@@ -111,12 +112,13 @@ tracepoint_entry_add_probe(struct tracep
return ERR_PTR(-EEXIST);
}
/* + 2 : one for new probe, one for NULL func */
- new = kzalloc((nr_probes + 2) * sizeof(void *), GFP_KERNEL);
+ new = allocate_probes(nr_probes + 2);
if (new == NULL)
return ERR_PTR(-ENOMEM);
if (old)
memcpy(new, old, nr_probes * sizeof(void *));
new[nr_probes] = probe;
+ new[nr_probes + 1] = NULL;
entry->refcount = nr_probes + 1;
entry->funcs = new;
debug_print_probes(entry);
@@ -132,7 +134,7 @@ tracepoint_entry_remove_probe(struct tra
old = entry->funcs;
if (!old)
- return NULL;
+ return ERR_PTR(-ENOENT);
debug_print_probes(entry);
/* (N -> M), (N > 1, M >= 0) probes */
@@ -151,13 +153,13 @@ tracepoint_entry_remove_probe(struct tra
int j = 0;
/* N -> M, (N > 1, M > 0) */
/* + 1 for NULL */
- new = kzalloc((nr_probes - nr_del + 1)
- * sizeof(void *), GFP_KERNEL);
+ new = allocate_probes(nr_probes - nr_del + 1);
if (new == NULL)
return ERR_PTR(-ENOMEM);
for (i = 0; old[i]; i++)
if ((probe && old[i] != probe))
new[j++] = old[i];
+ new[nr_probes - nr_del] = NULL;
entry->refcount = nr_probes - nr_del;
entry->funcs = new;
}
@@ -215,7 +217,6 @@ static struct tracepoint_entry *add_trac
memcpy(&e->name[0], name, name_len);
e->funcs = NULL;
e->refcount = 0;
- e->rcu_pending = 0;
hlist_add_head(&e->hlist, head);
return e;
}
@@ -224,32 +225,10 @@ static struct tracepoint_entry *add_trac
* Remove the tracepoint from the tracepoint hash table. Must be called with
* mutex_lock held.
*/
-static int remove_tracepoint(const char *name)
+static inline void remove_tracepoint(struct tracepoint_entry *e)
{
- struct hlist_head *head;
- struct hlist_node *node;
- struct tracepoint_entry *e;
- int found = 0;
- size_t len = strlen(name) + 1;
- u32 hash = jhash(name, len-1, 0);
-
- head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
- hlist_for_each_entry(e, node, head, hlist) {
- if (!strcmp(name, e->name)) {
- found = 1;
- break;
- }
- }
- if (!found)
- return -ENOENT;
- if (e->refcount)
- return -EBUSY;
hlist_del(&e->hlist);
- /* Make sure the call_rcu_sched has been executed */
- if (e->rcu_pending)
- rcu_barrier_sched();
kfree(e);
- return 0;
}
/*
@@ -343,25 +322,17 @@ int tracepoint_probe_register(const char
goto end;
}
}
- /*
- * If we detect that a call_rcu_sched is pending for this tracepoint,
- * make sure it's executed now.
- */
- if (entry->rcu_pending)
- rcu_barrier_sched();
old = tracepoint_entry_add_probe(entry, probe);
if (IS_ERR(old)) {
+ if (!entry->refcount)
+ remove_tracepoint(entry);
ret = PTR_ERR(old);
goto end;
}
mutex_unlock(&tracepoints_mutex);
tracepoint_update_probes(); /* may update entry */
- mutex_lock(&tracepoints_mutex);
- entry = get_tracepoint(name);
- WARN_ON(!entry);
- if (entry->rcu_pending)
- rcu_barrier_sched();
- tracepoint_entry_free_old(entry, old);
+ release_probes(old);
+ return 0;
end:
mutex_unlock(&tracepoints_mutex);
return ret;
@@ -388,25 +359,17 @@ int tracepoint_probe_unregister(const ch
entry = get_tracepoint(name);
if (!entry)
goto end;
- if (entry->rcu_pending)
- rcu_barrier_sched();
old = tracepoint_entry_remove_probe(entry, probe);
- if (!old) {
- printk(KERN_WARNING "Warning: Trying to unregister a probe"
- "that doesn't exist\n");
+ if (IS_ERR(old)) {
+ ret = PTR_ERR(old);
goto end;
}
+ if (!entry->refcount)
+ remove_tracepoint(entry);
mutex_unlock(&tracepoints_mutex);
tracepoint_update_probes(); /* may update entry */
- mutex_lock(&tracepoints_mutex);
- entry = get_tracepoint(name);
- if (!entry)
- goto end;
- if (entry->rcu_pending)
- rcu_barrier_sched();
- tracepoint_entry_free_old(entry, old);
- remove_tracepoint(name); /* Ignore busy error message */
- ret = 0;
+ release_probes(old);
+ return 0;
end:
mutex_unlock(&tracepoints_mutex);
return ret;
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
^ permalink raw reply [flat|nested] 3+ messages in thread* [patch 2/2] tracepoint: introduce *_noupdate APIs. (v2)
2008-10-31 0:26 [patch 0/2] Tracepoint updates for -tip mathieu.desnoyers
2008-10-31 0:27 ` [patch 1/2] tracepoint: simplify for tracepoint using RCU mathieu.desnoyers
@ 2008-10-31 0:27 ` mathieu.desnoyers
1 sibling, 0 replies; 3+ messages in thread
From: mathieu.desnoyers @ 2008-10-31 0:27 UTC (permalink / raw)
To: Ingo Molnar, linux-kernel; +Cc: Lai Jiangshan, Mathieu Desnoyers
[-- Attachment #1: tracepoint-introduce-noupdate-apis.patch --]
[-- Type: text/plain, Size: 7553 bytes --]
new APIs separate tracepoint_probe_register(),
tracepoint_probe_unregister() into 2 steps. The first step of them
is just update tracepoint_entry, not connect or disconnect.
this patch introduce tracepoint_probe_update_all() for update all.
these APIs are very useful for registering a lots of probes
but just update once only. and a very important thing is that
*_noupdate APIs do not require module_mutex.
Mathieu Desnoyers : Refreshed for -tip.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
---
include/linux/tracepoint.h | 4 +
kernel/tracepoint.c | 170 ++++++++++++++++++++++++++++++++++-----------
2 files changed, 136 insertions(+), 38 deletions(-)
Index: linux-2.6-lttng/include/linux/tracepoint.h
===================================================================
--- linux-2.6-lttng.orig/include/linux/tracepoint.h 2008-10-30 20:12:05.000000000 -0400
+++ linux-2.6-lttng/include/linux/tracepoint.h 2008-10-30 20:18:16.000000000 -0400
@@ -112,6 +112,10 @@ extern int tracepoint_probe_register(con
*/
extern int tracepoint_probe_unregister(const char *name, void *probe);
+extern int tracepoint_probe_register_noupdate(const char *name, void *probe);
+extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe);
+extern void tracepoint_probe_update_all(void);
+
struct tracepoint_iter {
struct module *module;
struct tracepoint *tracepoint;
Index: linux-2.6-lttng/kernel/tracepoint.c
===================================================================
--- linux-2.6-lttng.orig/kernel/tracepoint.c 2008-10-30 20:17:25.000000000 -0400
+++ linux-2.6-lttng/kernel/tracepoint.c 2008-10-30 20:18:16.000000000 -0400
@@ -59,7 +59,10 @@ struct tracepoint_entry {
};
struct tp_probes {
- struct rcu_head rcu;
+ union {
+ struct rcu_head rcu;
+ struct list_head list;
+ } u;
void *probes[0];
};
@@ -72,7 +75,7 @@ static inline void *allocate_probes(int
static void rcu_free_old_probes(struct rcu_head *head)
{
- kfree(container_of(head, struct tp_probes, rcu));
+ kfree(container_of(head, struct tp_probes, u.rcu));
}
static inline void release_probes(void *old)
@@ -80,7 +83,7 @@ static inline void release_probes(void *
if (old) {
struct tp_probes *tp_probes = container_of(old,
struct tp_probes, probes[0]);
- call_rcu(&tp_probes->rcu, rcu_free_old_probes);
+ call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
}
}
@@ -299,6 +302,23 @@ static void tracepoint_update_probes(voi
module_update_tracepoints();
}
+static void *tracepoint_add_probe(const char *name, void *probe)
+{
+ struct tracepoint_entry *entry;
+ void *old;
+
+ entry = get_tracepoint(name);
+ if (!entry) {
+ entry = add_tracepoint(name);
+ if (IS_ERR(entry))
+ return entry;
+ }
+ old = tracepoint_entry_add_probe(entry, probe);
+ if (IS_ERR(old) && !entry->refcount)
+ remove_tracepoint(entry);
+ return old;
+}
+
/**
* tracepoint_probe_register - Connect a probe to a tracepoint
* @name: tracepoint name
@@ -309,36 +329,36 @@ static void tracepoint_update_probes(voi
*/
int tracepoint_probe_register(const char *name, void *probe)
{
- struct tracepoint_entry *entry;
- int ret = 0;
void *old;
mutex_lock(&tracepoints_mutex);
- entry = get_tracepoint(name);
- if (!entry) {
- entry = add_tracepoint(name);
- if (IS_ERR(entry)) {
- ret = PTR_ERR(entry);
- goto end;
- }
- }
- old = tracepoint_entry_add_probe(entry, probe);
- if (IS_ERR(old)) {
- if (!entry->refcount)
- remove_tracepoint(entry);
- ret = PTR_ERR(old);
- goto end;
- }
+ old = tracepoint_add_probe(name, probe);
mutex_unlock(&tracepoints_mutex);
+ if (IS_ERR(old))
+ return PTR_ERR(old);
+
tracepoint_update_probes(); /* may update entry */
release_probes(old);
return 0;
-end:
- mutex_unlock(&tracepoints_mutex);
- return ret;
}
EXPORT_SYMBOL_GPL(tracepoint_probe_register);
+static void *tracepoint_remove_probe(const char *name, void *probe)
+{
+ struct tracepoint_entry *entry;
+ void *old;
+
+ entry = get_tracepoint(name);
+ if (!entry)
+ return ERR_PTR(-ENOENT);
+ old = tracepoint_entry_remove_probe(entry, probe);
+ if (IS_ERR(old))
+ return old;
+ if (!entry->refcount)
+ remove_tracepoint(entry);
+ return old;
+}
+
/**
* tracepoint_probe_unregister - Disconnect a probe from a tracepoint
* @name: tracepoint name
@@ -351,31 +371,105 @@ EXPORT_SYMBOL_GPL(tracepoint_probe_regis
*/
int tracepoint_probe_unregister(const char *name, void *probe)
{
- struct tracepoint_entry *entry;
void *old;
- int ret = -ENOENT;
mutex_lock(&tracepoints_mutex);
- entry = get_tracepoint(name);
- if (!entry)
- goto end;
- old = tracepoint_entry_remove_probe(entry, probe);
- if (IS_ERR(old)) {
- ret = PTR_ERR(old);
- goto end;
- }
- if (!entry->refcount)
- remove_tracepoint(entry);
+ old = tracepoint_remove_probe(name, probe);
mutex_unlock(&tracepoints_mutex);
+ if (IS_ERR(old))
+ return PTR_ERR(old);
+
tracepoint_update_probes(); /* may update entry */
release_probes(old);
return 0;
-end:
- mutex_unlock(&tracepoints_mutex);
- return ret;
}
EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
+static LIST_HEAD(old_probes);
+static int need_update;
+
+static void tracepoint_add_old_probes(void *old)
+{
+ need_update = 1;
+ if (old) {
+ struct tp_probes *tp_probes = container_of(old,
+ struct tp_probes, probes[0]);
+ list_add(&tp_probes->u.list, &old_probes);
+ }
+}
+
+/**
+ * tracepoint_probe_register_noupdate - register a probe but not connect
+ * @name: tracepoint name
+ * @probe: probe handler
+ *
+ * caller must call tracepoint_probe_update_all()
+ */
+int tracepoint_probe_register_noupdate(const char *name, void *probe)
+{
+ void *old;
+
+ mutex_lock(&tracepoints_mutex);
+ old = tracepoint_add_probe(name, probe);
+ if (IS_ERR(old)) {
+ mutex_unlock(&tracepoints_mutex);
+ return PTR_ERR(old);
+ }
+ tracepoint_add_old_probes(old);
+ mutex_unlock(&tracepoints_mutex);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
+
+/**
+ * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
+ * @name: tracepoint name
+ * @probe: probe function pointer
+ *
+ * caller must call tracepoint_probe_update_all()
+ */
+int tracepoint_probe_unregister_noupdate(const char *name, void *probe)
+{
+ void *old;
+
+ mutex_lock(&tracepoints_mutex);
+ old = tracepoint_remove_probe(name, probe);
+ if (IS_ERR(old)) {
+ mutex_unlock(&tracepoints_mutex);
+ return PTR_ERR(old);
+ }
+ tracepoint_add_old_probes(old);
+ mutex_unlock(&tracepoints_mutex);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
+
+/**
+ * tracepoint_probe_update_all - update tracepoints
+ */
+void tracepoint_probe_update_all(void)
+{
+ LIST_HEAD(release_probes);
+ struct tp_probes *pos, *next;
+
+ mutex_lock(&tracepoints_mutex);
+ if (!need_update) {
+ mutex_unlock(&tracepoints_mutex);
+ return;
+ }
+ if (!list_empty(&old_probes))
+ list_replace_init(&old_probes, &release_probes);
+ need_update = 0;
+ mutex_unlock(&tracepoints_mutex);
+
+ tracepoint_update_probes();
+ list_for_each_entry_safe(pos, next, &release_probes, u.list) {
+ list_del(&pos->u.list);
+ call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
+ }
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
+
/**
* tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
* @tracepoint: current tracepoints (in), next tracepoint (out)
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
^ permalink raw reply [flat|nested] 3+ messages in thread