Register/unregister tracepoint probes with struct tracepoint pointer
rather than tracepoint name.
This change, which vastly simplifies tracepoint.c, has been proposed by
Steven Rostedt.
>From this point on, the tracers need to pass a struct tracepoint pointer
to probe register/unregister. A probe can now only be connected to a
tracepoint that exists. Moreover, tracers are responsible for
unregistering the probe before the module containing its associated
tracepoint is unloaded.
This patch is currently only compile-tested for kernel/tracepoint.o. The
callers still need to be adapted.
Not-Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
CC: Steven Rostedt <rost...@goodmis.org>
CC: Ingo Molnar <mi...@kernel.org>
CC: Frederic Weisbecker <fweis...@gmail.com>
CC: Andrew Morton <a...@linux-foundation.org>
CC: Frank Ch. Eigler <f...@redhat.com>
CC: Johannes Berg <johannes.b...@intel.com>
---
include/linux/tracepoint.h | 7 +-
kernel/tracepoint.c | 440 +++++++++++---------------------------------
2 files changed, 116 insertions(+), 331 deletions(-)
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 812b255..f7bbd63 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -39,14 +39,15 @@ struct tracepoint {
* Connect a probe to a tracepoint.
* Internal API, should not be used directly.
*/
-extern int tracepoint_probe_register(const char *name, void *probe, void
*data);
+extern int tracepoint_probe_register(struct tracepoint *tp, void *probe,
+ void *data);
/*
* Disconnect a probe from a tracepoint.
* Internal API, should not be used directly.
*/
-extern int
-tracepoint_probe_unregister(const char *name, void *probe, void *data);
+extern int tracepoint_probe_unregister(struct tracepoint *tp, void *probe,
+ void *data);
#ifdef CONFIG_MODULES
struct tp_module {
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index cc6c8b6..97f0517 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -27,44 +27,19 @@
#include <linux/sched.h>
#include <linux/static_key.h>
-extern struct tracepoint * const __start___tracepoints_ptrs[];
-extern struct tracepoint * const __stop___tracepoints_ptrs[];
-
/* Set to 1 to enable tracepoint debug output */
static const int tracepoint_debug;
/*
- * Tracepoints mutex protects the builtin and module tracepoints and the hash
- * table, as well as the local module list.
+ * Tracepoints mutex protects the builtin and module tracepoints.
*/
static DEFINE_MUTEX(tracepoints_mutex);
-#ifdef CONFIG_MODULES
-/* Local list of struct module */
-static LIST_HEAD(tracepoint_module_list);
-#endif /* CONFIG_MODULES */
-
-/*
- * Tracepoint hash table, containing the active tracepoints.
- * Protected by 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 :
* It is used to delay the free of multiple probes array until a quiescent
* state is reached.
- * Tracepoint entries modifications are protected by the tracepoints_mutex.
*/
-struct tracepoint_entry {
- struct hlist_node hlist;
- struct tracepoint_func *funcs;
- int refcount; /* Number of times armed. 0 if disarmed. */
- char name[0];
-};
-
struct tp_probes {
union {
struct rcu_head rcu;
@@ -94,34 +69,35 @@ static inline void release_probes(struct tracepoint_func
*old)
}
}
-static void debug_print_probes(struct tracepoint_entry *entry)
+static
+void debug_print_probes(struct tracepoint_func *funcs)
{
int i;
- if (!tracepoint_debug || !entry->funcs)
+ if (!tracepoint_debug || !funcs)
return;
- for (i = 0; entry->funcs[i].func; i++)
- printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
+ for (i = 0; funcs[i].func; i++)
+ printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
}
-static struct tracepoint_func *
-tracepoint_entry_add_probe(struct tracepoint_entry *entry,
- void *probe, void *data)
+static
+struct tracepoint_func *func_add(struct tracepoint_func **funcs,
+ struct tracepoint_func *tp_func)
{
int nr_probes = 0;
struct tracepoint_func *old, *new;
- if (WARN_ON(!probe))
+ if (WARN_ON(!tp_func->func))
return ERR_PTR(-EINVAL);
- debug_print_probes(entry);
- old = entry->funcs;
+ debug_print_probes(*funcs);
+ old = *funcs;
if (old) {
/* (N -> N+1), (N != 0, 1) probes */
for (nr_probes = 0; old[nr_probes].func; nr_probes++)
- if (old[nr_probes].func == probe &&
- old[nr_probes].data == data)
+ if (old[nr_probes].func == tp_func->func &&
+ old[nr_probes].data == tp_func->data)
return ERR_PTR(-EEXIST);
}
/* + 2 : one for new probe, one for NULL func */
@@ -130,33 +106,31 @@ tracepoint_entry_add_probe(struct tracepoint_entry *entry,
return ERR_PTR(-ENOMEM);
if (old)
memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
- new[nr_probes].func = probe;
- new[nr_probes].data = data;
+ new[nr_probes] = *tp_func;
new[nr_probes + 1].func = NULL;
- entry->refcount = nr_probes + 1;
- entry->funcs = new;
- debug_print_probes(entry);
+ *funcs = new;
+ debug_print_probes(*funcs);
return old;
}
-static void *
-tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
- void *probe, void *data)
+static
+void *func_remove(struct tracepoint_func **funcs,
+ struct tracepoint_func *tp_func)
{
int nr_probes = 0, nr_del = 0, i;
struct tracepoint_func *old, *new;
- old = entry->funcs;
+ old = *funcs;
if (!old)
return ERR_PTR(-ENOENT);
- debug_print_probes(entry);
+ debug_print_probes(*funcs);
/* (N -> M), (N > 1, M >= 0) probes */
- if (probe) {
+ if (tp_func->func) {
for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
- if (old[nr_probes].func == probe &&
- old[nr_probes].data == data)
+ if (old[nr_probes].func == tp_func->func &&
+ old[nr_probes].data == tp_func->data)
nr_del++;
}
}
@@ -167,9 +141,8 @@ tracepoint_entry_remove_probe(struct tracepoint_entry
*entry,
*/
if (nr_probes - nr_del == 0) {
/* N -> 0, (N > 1) */
- entry->funcs = NULL;
- entry->refcount = 0;
- debug_print_probes(entry);
+ *funcs = NULL;
+ debug_print_probes(*funcs);
return old;
} else {
int j = 0;
@@ -179,90 +152,35 @@ tracepoint_entry_remove_probe(struct tracepoint_entry
*entry,
if (new == NULL)
return ERR_PTR(-ENOMEM);
for (i = 0; old[i].func; i++)
- if (old[i].func != probe || old[i].data != data)
+ if (old[i].func != tp_func->func
+ || old[i].data != tp_func->data)
new[j++] = old[i];
new[nr_probes - nr_del].func = NULL;
- entry->refcount = nr_probes - nr_del;
- entry->funcs = new;
+ *funcs = new;
}
- debug_print_probes(entry);
+ debug_print_probes(*funcs);
return old;
}
/*
- * Get tracepoint if the tracepoint is present in the tracepoint hash table.
- * Must be called with tracepoints_mutex held.
- * Returns NULL if not present.
+ * Add the probe function to a tracepoint.
*/
-static struct tracepoint_entry *get_tracepoint(const char *name)
+static
+int tracepoint_add_func(struct tracepoint *tp,
+ struct tracepoint_func *func)
{
- struct hlist_head *head;
- struct tracepoint_entry *e;
- u32 hash = jhash(name, strlen(name), 0);
-
- head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
- hlist_for_each_entry(e, head, hlist) {
- if (!strcmp(name, e->name))
- return e;
- }
- return NULL;
-}
+ struct tracepoint_func *old, *tp_funcs;
-/*
- * Add the tracepoint to the tracepoint hash table. Must be called with
- * tracepoints_mutex held.
- */
-static struct tracepoint_entry *add_tracepoint(const char *name)
-{
- struct hlist_head *head;
- struct tracepoint_entry *e;
- size_t name_len = strlen(name) + 1;
- u32 hash = jhash(name, name_len-1, 0);
-
- head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
- hlist_for_each_entry(e, head, hlist) {
- if (!strcmp(name, e->name)) {
- printk(KERN_NOTICE
- "tracepoint %s busy\n", name);
- return ERR_PTR(-EEXIST); /* Already there */
- }
- }
- /*
- * Using kmalloc here to allocate a variable length element. Could
- * cause some memory fragmentation if overused.
- */
- e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
- if (!e)
- return ERR_PTR(-ENOMEM);
- memcpy(&e->name[0], name, name_len);
- e->funcs = NULL;
- e->refcount = 0;
- hlist_add_head(&e->hlist, head);
- return e;
-}
+ if (tp->regfunc && !static_key_enabled(&tp->key))
+ tp->regfunc();
-/*
- * Remove the tracepoint from the tracepoint hash table. Must be called with
- * mutex_lock held.
- */
-static inline void remove_tracepoint(struct tracepoint_entry *e)
-{
- hlist_del(&e->hlist);
- kfree(e);
-}
-
-/*
- * Sets the probe callback corresponding to one tracepoint.
- */
-static void set_tracepoint(struct tracepoint_entry **entry,
- struct tracepoint *elem, int active)
-{
- WARN_ON(strcmp((*entry)->name, elem->name) != 0);
-
- if (elem->regfunc && !static_key_enabled(&elem->key) && active)
- elem->regfunc();
- else if (elem->unregfunc && static_key_enabled(&elem->key) && !active)
- elem->unregfunc();
+ tp_funcs = tp->funcs;
+ old = func_add(&tp_funcs, func);
+ if (IS_ERR(old)) {
+ WARN_ON_ONCE(1);
+ return PTR_ERR(old);
+ }
+ release_probes(old);
/*
* rcu_assign_pointer has a smp_wmb() which makes sure that the new
@@ -271,272 +189,138 @@ static void set_tracepoint(struct tracepoint_entry
**entry,
* include/linux/tracepoints.h. A matching smp_read_barrier_depends()
* is used.
*/
- rcu_assign_pointer(elem->funcs, (*entry)->funcs);
- if (active && !static_key_enabled(&elem->key))
- static_key_slow_inc(&elem->key);
- else if (!active && static_key_enabled(&elem->key))
- static_key_slow_dec(&elem->key);
+ rcu_assign_pointer(tp->funcs, tp_funcs);
+ if (!static_key_enabled(&tp->key))
+ static_key_slow_inc(&tp->key);
+ return 0;
}
/*
- * Disable a tracepoint and its probe callback.
+ * Remove a probe function from a tracepoint.
* 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_tracepoint(struct tracepoint *elem)
-{
- if (elem->unregfunc && static_key_enabled(&elem->key))
- elem->unregfunc();
-
- if (static_key_enabled(&elem->key))
- static_key_slow_dec(&elem->key);
- rcu_assign_pointer(elem->funcs, NULL);
-}
-
-/**
- * tracepoint_update_probe_range - Update a probe range
- * @begin: beginning of the range
- * @end: end of the range
- *
- * Updates the probe callback corresponding to a range of tracepoints.
- * Called with tracepoints_mutex held.
- */
-static void tracepoint_update_probe_range(struct tracepoint * const *begin,
- struct tracepoint * const *end)
+static
+int tracepoint_remove_func(struct tracepoint *tp,
+ struct tracepoint_func *func)
{
- struct tracepoint * const *iter;
- struct tracepoint_entry *mark_entry;
-
- if (!begin)
- return;
+ struct tracepoint_func *old, *tp_funcs;
- for (iter = begin; iter < end; iter++) {
- mark_entry = get_tracepoint((*iter)->name);
- if (mark_entry) {
- set_tracepoint(&mark_entry, *iter,
- !!mark_entry->refcount);
- } else {
- disable_tracepoint(*iter);
- }
+ tp_funcs = tp->funcs;
+ old = func_remove(&tp_funcs, func);
+ if (IS_ERR(old)) {
+ WARN_ON_ONCE(1);
+ return PTR_ERR(old);
}
-}
-
-#ifdef CONFIG_MODULES
-void module_update_tracepoints(void)
-{
- struct tp_module *tp_mod;
-
- list_for_each_entry(tp_mod, &tracepoint_module_list, list)
- tracepoint_update_probe_range(tp_mod->tracepoints_ptrs,
- tp_mod->tracepoints_ptrs + tp_mod->num_tracepoints);
-}
-#else /* CONFIG_MODULES */
-void module_update_tracepoints(void)
-{
-}
-#endif /* CONFIG_MODULES */
-
+ release_probes(old);
-/*
- * Update probes, removing the faulty probes.
- * Called with tracepoints_mutex held.
- */
-static void tracepoint_update_probes(void)
-{
- /* Core kernel tracepoints */
- tracepoint_update_probe_range(__start___tracepoints_ptrs,
- __stop___tracepoints_ptrs);
- /* tracepoints in modules. */
- module_update_tracepoints();
-}
+ if (!tp_funcs) {
+ /* Removed last function */
+ if (tp->unregfunc && static_key_enabled(&tp->key))
+ tp->unregfunc();
-static struct tracepoint_func *
-tracepoint_add_probe(const char *name, void *probe, void *data)
-{
- struct tracepoint_entry *entry;
- struct tracepoint_func *old;
-
- entry = get_tracepoint(name);
- if (!entry) {
- entry = add_tracepoint(name);
- if (IS_ERR(entry))
- return (struct tracepoint_func *)entry;
+ if (static_key_enabled(&tp->key))
+ static_key_slow_dec(&tp->key);
}
- old = tracepoint_entry_add_probe(entry, probe, data);
- if (IS_ERR(old) && !entry->refcount)
- remove_tracepoint(entry);
- return old;
+ rcu_assign_pointer(tp->funcs, tp_funcs);
+ return 0;
}
/**
* tracepoint_probe_register - Connect a probe to a tracepoint
- * @name: tracepoint name
+ * @tp: tracepoint
* @probe: probe handler
* @data: probe private data
*
* Returns 0 if ok, error value on error.
- * The probe address must at least be aligned on the architecture pointer size.
+ * Note: if @tp is within a module, the caller is responsible for
+ * monitoring the module "going" notifier to unregister the probe before
+ * the module is gone.
*/
-int tracepoint_probe_register(const char *name, void *probe, void *data)
+int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
{
- struct tracepoint_func *old;
+ struct tracepoint_func tp_func;
+ int ret;
mutex_lock(&tracepoints_mutex);
- old = tracepoint_add_probe(name, probe, data);
- if (IS_ERR(old)) {
- mutex_unlock(&tracepoints_mutex);
- return PTR_ERR(old);
- }
- tracepoint_update_probes(); /* may update entry */
+ tp_func.func = probe;
+ tp_func.data = data;
+ ret = tracepoint_add_func(tp, &tp_func);
mutex_unlock(&tracepoints_mutex);
- release_probes(old);
- return 0;
+ return ret;
}
EXPORT_SYMBOL_GPL(tracepoint_probe_register);
-static struct tracepoint_func *
-tracepoint_remove_probe(const char *name, void *probe, void *data)
-{
- struct tracepoint_entry *entry;
- struct tracepoint_func *old;
-
- entry = get_tracepoint(name);
- if (!entry)
- return ERR_PTR(-ENOENT);
- old = tracepoint_entry_remove_probe(entry, probe, data);
- 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
+ * @tp: tracepoint
* @probe: probe function pointer
* @data: probe private data
*
- * We do not need to call a synchronize_sched to make sure the probes have
- * finished running before doing a module unload, because the module unload
- * itself uses stop_machine(), which insures that every preempt disabled
section
- * have finished.
+ * Returns 0 if ok, error value on error.
*/
-int tracepoint_probe_unregister(const char *name, void *probe, void *data)
+int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
{
- struct tracepoint_func *old;
+ struct tracepoint_func tp_func;
+ int ret;
mutex_lock(&tracepoints_mutex);
- old = tracepoint_remove_probe(name, probe, data);
- if (IS_ERR(old)) {
- mutex_unlock(&tracepoints_mutex);
- return PTR_ERR(old);
- }
- tracepoint_update_probes(); /* may update entry */
+ tp_func.func = probe;
+ tp_func.data = data;
+ ret = tracepoint_remove_func(tp, &tp_func);
mutex_unlock(&tracepoints_mutex);
- release_probes(old);
- return 0;
+ 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);
- }
-}
-
#ifdef CONFIG_MODULES
bool trace_module_has_bad_taint(struct module *mod)
{
return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP));
}
-static int tracepoint_module_coming(struct module *mod)
+/*
+ * Ensure the tracer unregistered the module's probes before the module
+ * teardown is performed. Prevents leaks of probe and data pointers.
+ */
+static
+void tp_module_going_check_quiescent(struct tracepoint * const *begin,
+ struct tracepoint * const *end)
{
- struct tp_module *tp_mod, *iter;
- int ret = 0;
-
- /*
- * We skip modules that taint the kernel, especially those with
different
- * module headers (for forced load), to make sure we don't cause a
crash.
- * Staging and out-of-tree GPL modules are fine.
- */
- if (trace_module_has_bad_taint(mod))
- return 0;
- mutex_lock(&tracepoints_mutex);
- tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
- if (!tp_mod) {
- ret = -ENOMEM;
- goto end;
- }
- tp_mod->num_tracepoints = mod->num_tracepoints;
- tp_mod->tracepoints_ptrs = mod->tracepoints_ptrs;
+ struct tracepoint * const *iter;
- /*
- * tracepoint_module_list is kept sorted by struct module pointer
- * address for iteration on tracepoints from a seq_file that can release
- * the mutex between calls.
- */
- list_for_each_entry_reverse(iter, &tracepoint_module_list, list) {
- BUG_ON(iter == tp_mod); /* Should never be in the list twice */
- if (iter < tp_mod) {
- /* We belong to the location right after iter. */
- list_add(&tp_mod->list, &iter->list);
- goto module_added;
- }
- }
- /* We belong to the beginning of the list */
- list_add(&tp_mod->list, &tracepoint_module_list);
-module_added:
- tracepoint_update_probe_range(mod->tracepoints_ptrs,
- mod->tracepoints_ptrs + mod->num_tracepoints);
-end:
- mutex_unlock(&tracepoints_mutex);
- return ret;
+ if (!begin)
+ return;
+ for (iter = begin; iter < end; iter++)
+ WARN_ON_ONCE((*iter)->funcs);
}
-static int tracepoint_module_going(struct module *mod)
+static
+int tracepoint_module_going(struct module *mod)
{
- struct tp_module *pos;
-
- mutex_lock(&tracepoints_mutex);
- tracepoint_update_probe_range(mod->tracepoints_ptrs,
- mod->tracepoints_ptrs + mod->num_tracepoints);
- list_for_each_entry(pos, &tracepoint_module_list, list) {
- if (pos->tracepoints_ptrs == mod->tracepoints_ptrs) {
- list_del(&pos->list);
- kfree(pos);
- break;
- }
- }
/*
- * In the case of modules that were tainted at "coming", we'll simply
- * walk through the list without finding it. We cannot use the "tainted"
- * flag on "going", in case a module taints the kernel only after being
- * loaded.
+ * We skip modules that taint the kernel, especially those with
+ * different module headers (for forced load), to make sure we
+ * don't cause a crash. Staging and out-of-tree GPL modules are
+ * fine.
*/
- mutex_unlock(&tracepoints_mutex);
+ if (trace_module_has_bad_taint(mod))
+ return 0;
+ tp_module_going_check_quiescent(mod->tracepoints_ptrs,
+ mod->tracepoints_ptrs + mod->num_tracepoints);
return 0;
}
+static
int tracepoint_module_notify(struct notifier_block *self,
- unsigned long val, void *data)
+ unsigned long val, void *data)
{
struct module *mod = data;
int ret = 0;
switch (val) {
case MODULE_STATE_COMING:
- ret = tracepoint_module_coming(mod);
- break;
case MODULE_STATE_LIVE:
break;
case MODULE_STATE_GOING:
--
1.7.10.4
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