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Linux Kernel Markers: support multiple probes

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RCU style multiple probes support for the Linux Kernel Markers.  Common case
(one probe) is still fast and does not require dynamic allocation or a
supplementary pointer dereference on the fast path.

- Move preempt disable from the marker site to the callback.

Since we now have an internal callback, move the preempt disable/enable to the
callback instead of the marker site.

Since the callback change is done asynchronously (passing from a handler that
supports arguments to a handler that does not setup the arguments is no
arguments are passed), we can safely update it even if it is outside the
preempt disable section.

- Move probe arm to probe connection. Now, a connected probe is automatically
  armed.

Remove MARK_MAX_FORMAT_LEN, unused.

This patch modifies the Linux Kernel Markers API : it removes the probe
"arm/disarm" and changes the probe function prototype : it now expects a
va_list * instead of a "...".

If we want to have more than one probe connected to a marker at a given
time (LTTng, or blktrace, ssytemtap) then we need this patch. Without it,
connecting a second probe handler to a marker will fail.

It allow us, for instance, to do interesting combinations :

Do standard tracing with LTTng and, eventually, to compute statistics
with SystemTAP, or to have a special trigger on an event that would call
a systemtap script which would stop flight recorder tracing.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Christoph Hellwig <hch@infradead.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: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mathieu Desnoyers 2008-02-13 15:03:37 -08:00 committed by Linus Torvalds
parent 9170d2f6e1
commit fb40bd78b0
6 changed files with 579 additions and 250 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

31
arch/powerpc/platforms/cell/spufs/sputrace.c
View file

@ -146,34 +146,28 @@ static void sputrace_log_item(const char *name, struct spu_context *ctx,
wake_up(&sputrace_wait);
}
static void spu_context_event(const struct marker *mdata,
void *private, const char *format, ...)
static void spu_context_event(void *probe_private, void *call_data,
const char *format, va_list *args)
{
struct spu_probe *p = mdata->private;
va_list ap;
struct spu_probe *p = probe_private;
struct spu_context *ctx;
struct spu *spu;
va_start(ap, format);
ctx = va_arg(ap, struct spu_context *);
spu = va_arg(ap, struct spu *);
ctx = va_arg(*args, struct spu_context *);
spu = va_arg(*args, struct spu *);
sputrace_log_item(p->name, ctx, spu);
va_end(ap);
}
static void spu_context_nospu_event(const struct marker *mdata,
void *private, const char *format, ...)
static void spu_context_nospu_event(void *probe_private, void *call_data,
const char *format, va_list *args)
{
struct spu_probe *p = mdata->private;
va_list ap;
struct spu_probe *p = probe_private;
struct spu_context *ctx;
va_start(ap, format);
ctx = va_arg(ap, struct spu_context *);
ctx = va_arg(*args, struct spu_context *);
sputrace_log_item(p->name, ctx, NULL);
va_end(ap);
}
struct spu_probe spu_probes[] = {
@ -219,10 +213,6 @@ static int __init sputrace_init(void)
if (error)
printk(KERN_INFO "Unable to register probe %s\n",
p->name);
error = marker_arm(p->name);
if (error)
printk(KERN_INFO "Unable to arm probe %s\n", p->name);
}
return 0;
@ -238,7 +228,8 @@ static void __exit sputrace_exit(void)
int i;
for (i = 0; i < ARRAY_SIZE(spu_probes); i++)
marker_probe_unregister(spu_probes[i].name);
marker_probe_unregister(spu_probes[i].name,
spu_probes[i].probe_func, &spu_probes[i]);
remove_proc_entry("sputrace", NULL);
kfree(sputrace_log);

59
include/linux/marker.h
View file

@ -19,16 +19,23 @@ struct marker;
/**
* marker_probe_func - Type of a marker probe function
* @mdata: pointer of type struct marker
* @private_data: caller site private data
* @probe_private: probe private data
* @call_private: call site private data
* @fmt: format string
* @...: variable argument list
* @args: variable argument list pointer. Use a pointer to overcome C's
* inability to pass this around as a pointer in a portable manner in
* the callee otherwise.
*
* Type of marker probe functions. They receive the mdata and need to parse the
* format string to recover the variable argument list.
*/
typedef void marker_probe_func(const struct marker *mdata,
void *private_data, const char *fmt, ...);
typedef void marker_probe_func(void *probe_private, void *call_private,
const char *fmt, va_list *args);
struct marker_probe_closure {
marker_probe_func *func; /* Callback */
void *probe_private; /* Private probe data */
};
struct marker {
const char *name; /* Marker name */
@ -36,8 +43,11 @@ struct marker {
* variable argument list.
*/
char state; /* Marker state. */
marker_probe_func *call;/* Probe handler function pointer */
void *private; /* Private probe data */
char ptype; /* probe type : 0 : single, 1 : multi */
void (*call)(const struct marker *mdata, /* Probe wrapper */
void *call_private, const char *fmt, ...);
struct marker_probe_closure single;
struct marker_probe_closure *multi;
} __attribute__((aligned(8)));
#ifdef CONFIG_MARKERS
@ -49,7 +59,7 @@ struct marker {
* not add unwanted padding between the beginning of the section and the
* structure. Force alignment to the same alignment as the section start.
*/
#define __trace_mark(name, call_data, format, args...) \
#define __trace_mark(name, call_private, format, args...) \
do { \
static const char __mstrtab_name_##name[] \
__attribute__((section("__markers_strings"))) \
@ -60,24 +70,23 @@ struct marker {
static struct marker __mark_##name \
__attribute__((section("__markers"), aligned(8))) = \
{ __mstrtab_name_##name, __mstrtab_format_##name, \
0, __mark_empty_function, NULL }; \
0, 0, marker_probe_cb, \
{ __mark_empty_function, NULL}, NULL }; \
__mark_check_format(format, ## args); \
if (unlikely(__mark_##name.state)) { \
preempt_disable(); \
(*__mark_##name.call) \
(&__mark_##name, call_data, \
(&__mark_##name, call_private, \
format, ## args); \
preempt_enable(); \
} \
} while (0)
extern void marker_update_probe_range(struct marker *begin,
struct marker *end, struct module *probe_module, int *refcount);
struct marker *end);
#else /* !CONFIG_MARKERS */
#define __trace_mark(name, call_data, format, args...) \
#define __trace_mark(name, call_private, format, args...) \
__mark_check_format(format, ## args)
static inline void marker_update_probe_range(struct marker *begin,
struct marker *end, struct module *probe_module, int *refcount)
struct marker *end)
{ }
#endif /* CONFIG_MARKERS */
@ -92,8 +101,6 @@ static inline void marker_update_probe_range(struct marker *begin,
#define trace_mark(name, format, args...) \
__trace_mark(name, NULL, format, ## args)
#define MARK_MAX_FORMAT_LEN 1024
/**
* MARK_NOARGS - Format string for a marker with no argument.
*/
@ -106,24 +113,30 @@ static inline void __printf(1, 2) __mark_check_format(const char *fmt, ...)
extern marker_probe_func __mark_empty_function;
extern void marker_probe_cb(const struct marker *mdata,
void *call_private, const char *fmt, ...);
extern void marker_probe_cb_noarg(const struct marker *mdata,
void *call_private, const char *fmt, ...);
/*
* Connect a probe to a marker.
* private data pointer must be a valid allocated memory address, or NULL.
*/
extern int marker_probe_register(const char *name, const char *format,
marker_probe_func *probe, void *private);
marker_probe_func *probe, void *probe_private);
/*
* Returns the private data given to marker_probe_register.
*/
extern void *marker_probe_unregister(const char *name);
extern int marker_probe_unregister(const char *name,
marker_probe_func *probe, void *probe_private);
/*
* Unregister a marker by providing the registered private data.
*/
extern void *marker_probe_unregister_private_data(void *private);
extern int marker_probe_unregister_private_data(marker_probe_func *probe,
void *probe_private);
extern int marker_arm(const char *name);
extern int marker_disarm(const char *name);
extern void *marker_get_private_data(const char *name);
extern void *marker_get_private_data(const char *name, marker_probe_func *probe,
int num);
#endif

2
include/linux/module.h
View file

@ -465,7 +465,7 @@ int unregister_module_notifier(struct notifier_block * nb);
extern void print_modules(void);
extern void module_update_markers(struct module *probe_module, int *refcount);
extern void module_update_markers(void);
#else /* !CONFIG_MODULES... */
#define EXPORT_SYMBOL(sym)

705
kernel/marker.c
View file

@ -27,21 +27,14 @@
extern struct marker __start___markers[];
extern struct marker __stop___markers[];
/*
* markers_mutex nests inside module_mutex. Markers mutex protects the builtin
* and module markers, the hash table and deferred_sync.
*/
static DEFINE_MUTEX(markers_mutex);
/* Set to 1 to enable marker debug output */
const int marker_debug;
/*
* Marker deferred synchronization.
* Upon marker probe_unregister, we delay call to synchronize_sched() to
* accelerate mass unregistration (only when there is no more reference to a
* given module do we call synchronize_sched()). However, we need to make sure
* every critical region has ended before we re-arm a marker that has been
* unregistered and then registered back with a different probe data.
* markers_mutex nests inside module_mutex. Markers mutex protects the builtin
* and module markers and the hash table.
*/
static int deferred_sync;
static DEFINE_MUTEX(markers_mutex);
/*
* Marker hash table, containing the active markers.
@ -50,12 +43,26 @@ static int deferred_sync;
#define MARKER_HASH_BITS 6
#define MARKER_TABLE_SIZE (1 << MARKER_HASH_BITS)
/*
* Note about RCU :
* It is used to make sure every handler has finished using its private data
* between two consecutive operation (add or remove) on a given marker. It is
* also used to delay the free of multiple probes array until a quiescent state
* is reached.
* marker entries modifications are protected by the markers_mutex.
*/
struct marker_entry {
struct hlist_node hlist;
char *format;
marker_probe_func *probe;
void *private;
void (*call)(const struct marker *mdata, /* Probe wrapper */
void *call_private, const char *fmt, ...);
struct marker_probe_closure single;
struct marker_probe_closure *multi;
int refcount; /* Number of times armed. 0 if disarmed. */
struct rcu_head rcu;
void *oldptr;
char rcu_pending:1;
char ptype:1;
char name[0]; /* Contains name'\0'format'\0' */
};
@ -63,7 +70,8 @@ static struct hlist_head marker_table[MARKER_TABLE_SIZE];
/**
* __mark_empty_function - Empty probe callback
* @mdata: pointer of type const struct marker
* @probe_private: probe private data
* @call_private: call site private data
* @fmt: format string
* @...: variable argument list
*
@ -72,12 +80,266 @@ static struct hlist_head marker_table[MARKER_TABLE_SIZE];
* though the function pointer change and the marker enabling are two distinct
* operations that modifies the execution flow of preemptible code.
*/
void __mark_empty_function(const struct marker *mdata, void *private,
const char *fmt, ...)
void __mark_empty_function(void *probe_private, void *call_private,
const char *fmt, va_list *args)
{
}
EXPORT_SYMBOL_GPL(__mark_empty_function);
/*
* marker_probe_cb Callback that prepares the variable argument list for probes.
* @mdata: pointer of type struct marker
* @call_private: caller site private data
* @fmt: format string
* @...: Variable argument list.
*
* Since we do not use "typical" pointer based RCU in the 1 argument case, we
* need to put a full smp_rmb() in this branch. This is why we do not use
* rcu_dereference() for the pointer read.
*/
void marker_probe_cb(const struct marker *mdata, void *call_private,
const char *fmt, ...)
{
va_list args;
char ptype;
/*
* disabling preemption to make sure the teardown of the callbacks can
* be done correctly when they are in modules and they insure RCU read
* coherency.
*/
preempt_disable();
ptype = ACCESS_ONCE(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);
/* Must read the ptr before private data. They are not data
* dependant, so we put an explicit smp_rmb() here. */
smp_rmb();
va_start(args, fmt);
func(mdata->single.probe_private, call_private, fmt, &args);
va_end(args);
} else {
struct marker_probe_closure *multi;
int i;
/*
* 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
* data. Same as rcu_dereference, but we need a full smp_rmb()
* in the fast path, so put the explicit barrier here.
*/
smp_read_barrier_depends();
multi = ACCESS_ONCE(mdata->multi);
for (i = 0; multi[i].func; i++) {
va_start(args, fmt);
multi[i].func(multi[i].probe_private, call_private, fmt,
&args);
va_end(args);
}
}
preempt_enable();
}
EXPORT_SYMBOL_GPL(marker_probe_cb);
/*
* marker_probe_cb Callback that does not prepare the variable argument list.
* @mdata: pointer of type struct marker
* @call_private: caller site private data
* @fmt: format string
* @...: Variable argument list.
*
* Should be connected to markers "MARK_NOARGS".
*/
void marker_probe_cb_noarg(const struct marker *mdata,
void *call_private, const char *fmt, ...)
{
va_list args; /* not initialized */
char ptype;
preempt_disable();
ptype = ACCESS_ONCE(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);
/* Must read the ptr before private data. They are not data
* dependant, so we put an explicit smp_rmb() here. */
smp_rmb();
func(mdata->single.probe_private, call_private, fmt, &args);
} else {
struct marker_probe_closure *multi;
int i;
/*
* 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
* data. Same as rcu_dereference, but we need a full smp_rmb()
* in the fast path, so put the explicit barrier here.
*/
smp_read_barrier_depends();
multi = ACCESS_ONCE(mdata->multi);
for (i = 0; multi[i].func; i++)
multi[i].func(multi[i].probe_private, call_private, fmt,
&args);
}
preempt_enable();
}
EXPORT_SYMBOL_GPL(marker_probe_cb_noarg);
static void free_old_closure(struct rcu_head *head)
{
struct marker_entry *entry = container_of(head,
struct marker_entry, rcu);
kfree(entry->oldptr);
/* Make sure we free the data before setting the pending flag to 0 */
smp_wmb();
entry->rcu_pending = 0;
}
static void debug_print_probes(struct marker_entry *entry)
{
int i;
if (!marker_debug)
return;
if (!entry->ptype) {
printk(KERN_DEBUG "Single probe : %p %p\n",
entry->single.func,
entry->single.probe_private);
} else {
for (i = 0; entry->multi[i].func; i++)
printk(KERN_DEBUG "Multi probe %d : %p %p\n", i,
entry->multi[i].func,
entry->multi[i].probe_private);
}
}
static struct marker_probe_closure *
marker_entry_add_probe(struct marker_entry *entry,
marker_probe_func *probe, void *probe_private)
{
int nr_probes = 0;
struct marker_probe_closure *old, *new;
WARN_ON(!probe);
debug_print_probes(entry);
old = entry->multi;
if (!entry->ptype) {
if (entry->single.func == probe &&
entry->single.probe_private == probe_private)
return ERR_PTR(-EBUSY);
if (entry->single.func == __mark_empty_function) {
/* 0 -> 1 probes */
entry->single.func = probe;
entry->single.probe_private = probe_private;
entry->refcount = 1;
entry->ptype = 0;
debug_print_probes(entry);
return NULL;
} else {
/* 1 -> 2 probes */
nr_probes = 1;
old = NULL;
}
} else {
/* (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].probe_private
== probe_private)
return ERR_PTR(-EBUSY);
}
/* + 2 : one for new probe, one for NULL func */
new = kzalloc((nr_probes + 2) * sizeof(struct marker_probe_closure),
GFP_KERNEL);
if (new == NULL)
return ERR_PTR(-ENOMEM);
if (!old)
new[0] = entry->single;
else
memcpy(new, old,
nr_probes * sizeof(struct marker_probe_closure));
new[nr_probes].func = probe;
new[nr_probes].probe_private = probe_private;
entry->refcount = nr_probes + 1;
entry->multi = new;
entry->ptype = 1;
debug_print_probes(entry);
return old;
}
static struct marker_probe_closure *
marker_entry_remove_probe(struct marker_entry *entry,
marker_probe_func *probe, void *probe_private)
{
int nr_probes = 0, nr_del = 0, i;
struct marker_probe_closure *old, *new;
old = entry->multi;
debug_print_probes(entry);
if (!entry->ptype) {
/* 0 -> N is an error */
WARN_ON(entry->single.func == __mark_empty_function);
/* 1 -> 0 probes */
WARN_ON(probe && entry->single.func != probe);
WARN_ON(entry->single.probe_private != probe_private);
entry->single.func = __mark_empty_function;
entry->refcount = 0;
entry->ptype = 0;
debug_print_probes(entry);
return NULL;
} else {
/* (N -> M), (N > 1, M >= 0) probes */
for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
if ((!probe || old[nr_probes].func == probe)
&& old[nr_probes].probe_private
== probe_private)
nr_del++;
}
}
if (nr_probes - nr_del == 0) {
/* N -> 0, (N > 1) */
entry->single.func = __mark_empty_function;
entry->refcount = 0;
entry->ptype = 0;
} else if (nr_probes - nr_del == 1) {
/* N -> 1, (N > 1) */
for (i = 0; old[i].func; i++)
if ((probe && old[i].func != probe) ||
old[i].probe_private != probe_private)
entry->single = old[i];
entry->refcount = 1;
entry->ptype = 0;
} else {
int j = 0;
/* N -> M, (N > 1, M > 1) */
/* + 1 for NULL */
new = kzalloc((nr_probes - nr_del + 1)
* sizeof(struct marker_probe_closure), GFP_KERNEL);
if (new == NULL)
return ERR_PTR(-ENOMEM);
for (i = 0; old[i].func; i++)
if ((probe && old[i].func != probe) ||
old[i].probe_private != probe_private)
new[j++] = old[i];
entry->refcount = nr_probes - nr_del;
entry->ptype = 1;
entry->multi = new;
}
debug_print_probes(entry);
return old;
}
/*
* Get marker if the marker is present in the marker hash table.
* Must be called with markers_mutex held.
@ -102,8 +364,7 @@ static struct marker_entry *get_marker(const char *name)
* Add the marker to the marker hash table. Must be called with markers_mutex
* held.
*/
static int add_marker(const char *name, const char *format,
marker_probe_func *probe, void *private)
static struct marker_entry *add_marker(const char *name, const char *format)
{
struct hlist_head *head;
struct hlist_node *node;
@ -118,9 +379,8 @@ static int add_marker(const char *name, const char *format,
hlist_for_each_entry(e, node, head, hlist) {
if (!strcmp(name, e->name)) {
printk(KERN_NOTICE
"Marker %s busy, probe %p already installed\n",
name, e->probe);
return -EBUSY; /* Already there */
"Marker %s busy\n", name);
return ERR_PTR(-EBUSY); /* Already there */
}
}
/*
@ -130,34 +390,42 @@ static int add_marker(const char *name, const char *format,
e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
GFP_KERNEL);
if (!e)
return -ENOMEM;
return ERR_PTR(-ENOMEM);
memcpy(&e->name[0], name, name_len);
if (format) {
e->format = &e->name[name_len];
memcpy(e->format, format, format_len);
if (strcmp(e->format, MARK_NOARGS) == 0)
e->call = marker_probe_cb_noarg;
else
e->call = marker_probe_cb;
trace_mark(core_marker_format, "name %s format %s",
e->name, e->format);
} else
} else {
e->format = NULL;
e->probe = probe;
e->private = private;
e->call = marker_probe_cb;
}
e->single.func = __mark_empty_function;
e->single.probe_private = NULL;
e->multi = NULL;
e->ptype = 0;
e->refcount = 0;
e->rcu_pending = 0;
hlist_add_head(&e->hlist, head);
return 0;
return e;
}
/*
* Remove the marker from the marker hash table. Must be called with mutex_lock
* held.
*/
static void *remove_marker(const char *name)
static int remove_marker(const char *name)
{
struct hlist_head *head;
struct hlist_node *node;
struct marker_entry *e;
int found = 0;
size_t len = strlen(name) + 1;
void *private = NULL;
u32 hash = jhash(name, len-1, 0);
head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
@ -167,12 +435,16 @@ static void *remove_marker(const char *name)
break;
}
}
if (found) {
private = e->private;
hlist_del(&e->hlist);
kfree(e);
}
return private;
if (!found)
return -ENOENT;
if (e->single.func != __mark_empty_function)
return -EBUSY;
hlist_del(&e->hlist);
/* Make sure the call_rcu has been executed */
if (e->rcu_pending)
rcu_barrier();
kfree(e);
return 0;
}
/*
@ -184,6 +456,7 @@ static int marker_set_format(struct marker_entry **entry, const char *format)
size_t name_len = strlen((*entry)->name) + 1;
size_t format_len = strlen(format) + 1;
e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
GFP_KERNEL);
if (!e)
@ -191,11 +464,20 @@ static int marker_set_format(struct marker_entry **entry, const char *format)
memcpy(&e->name[0], (*entry)->name, name_len);
e->format = &e->name[name_len];
memcpy(e->format, format, format_len);
e->probe = (*entry)->probe;
e->private = (*entry)->private;
if (strcmp(e->format, MARK_NOARGS) == 0)
e->call = marker_probe_cb_noarg;
else
e->call = marker_probe_cb;
e->single = (*entry)->single;
e->multi = (*entry)->multi;
e->ptype = (*entry)->ptype;
e->refcount = (*entry)->refcount;
e->rcu_pending = 0;
hlist_add_before(&e->hlist, &(*entry)->hlist);
hlist_del(&(*entry)->hlist);
/* Make sure the call_rcu has been executed */
if ((*entry)->rcu_pending)
rcu_barrier();
kfree(*entry);
*entry = e;
trace_mark(core_marker_format, "name %s format %s",
@ -206,7 +488,8 @@ static int marker_set_format(struct marker_entry **entry, const char *format)
/*
* Sets the probe callback corresponding to one marker.
*/
static int set_marker(struct marker_entry **entry, struct marker *elem)
static int set_marker(struct marker_entry **entry, struct marker *elem,
int active)
{
int ret;
WARN_ON(strcmp((*entry)->name, elem->name) != 0);
@ -226,9 +509,43 @@ static int set_marker(struct marker_entry **entry, struct marker *elem)
if (ret)
return ret;
}
elem->call = (*entry)->probe;
elem->private = (*entry)->private;
elem->state = 1;
/*
* probe_cb setup (statically known) is done here. It is
* asynchronous with the rest of execution, therefore we only
* pass from a "safe" callback (with argument) to an "unsafe"
* callback (does not set arguments).
*/
elem->call = (*entry)->call;
/*
* Sanity check :
* We only update the single probe private data when the ptr is
* set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
*/
WARN_ON(elem->single.func != __mark_empty_function
&& elem->single.probe_private
!= (*entry)->single.probe_private &&
!elem->ptype);
elem->single.probe_private = (*entry)->single.probe_private;
/*
* Make sure the private data is valid when we update the
* single probe ptr.
*/
smp_wmb();
elem->single.func = (*entry)->single.func;
/*
* We also make sure that the new probe callbacks array is consistent
* before setting a pointer to it.
*/
rcu_assign_pointer(elem->multi, (*entry)->multi);
/*
* Update the function or multi probe array pointer before setting the
* ptype.
*/
smp_wmb();
elem->ptype = (*entry)->ptype;
elem->state = active;
return 0;
}
@ -240,8 +557,12 @@ static int set_marker(struct marker_entry **entry, struct marker *elem)
*/
static void disable_marker(struct marker *elem)
{
/* leave "call" as is. It is known statically. */
elem->state = 0;
elem->call = __mark_empty_function;
elem->single.func = __mark_empty_function;
/* Update the function before setting the ptype */
smp_wmb();
elem->ptype = 0; /* single probe */
/*
* Leave the private data and id there, because removal is racy and
* should be done only after a synchronize_sched(). These are never used
@ -253,14 +574,11 @@ static void disable_marker(struct marker *elem)
* marker_update_probe_range - Update a probe range
* @begin: beginning of the range
* @end: end of the range
* @probe_module: module address of the probe being updated
* @refcount: number of references left to the given probe_module (out)
*
* Updates the probe callback corresponding to a range of markers.
*/
void marker_update_probe_range(struct marker *begin,
struct marker *end, struct module *probe_module,
int *refcount)
struct marker *end)
{
struct marker *iter;
struct marker_entry *mark_entry;
@ -268,15 +586,12 @@ void marker_update_probe_range(struct marker *begin,
mutex_lock(&markers_mutex);
for (iter = begin; iter < end; iter++) {
mark_entry = get_marker(iter->name);
if (mark_entry && mark_entry->refcount) {
set_marker(&mark_entry, iter);
if (mark_entry) {
set_marker(&mark_entry, iter,
!!mark_entry->refcount);
/*
* ignore error, continue
*/
if (probe_module)
if (probe_module ==
__module_text_address((unsigned long)mark_entry->probe))
(*refcount)++;
} else {
disable_marker(iter);
}
@ -289,20 +604,27 @@ void marker_update_probe_range(struct marker *begin,
* Issues a synchronize_sched() when no reference to the module passed
* as parameter is found in the probes so the probe module can be
* safely unloaded from now on.
*
* Internal callback only changed before the first probe is connected to it.
* Single probe private data can only be changed on 0 -> 1 and 2 -> 1
* transitions. All other transitions will leave the old private data valid.
* This makes the non-atomicity of the callback/private data updates valid.
*
* "special case" updates :
* 0 -> 1 callback
* 1 -> 0 callback
* 1 -> 2 callbacks
* 2 -> 1 callbacks
* Other updates all behave the same, just like the 2 -> 3 or 3 -> 2 updates.
* Site effect : marker_set_format may delete the marker entry (creating a
* replacement).
*/
static void marker_update_probes(struct module *probe_module)
static void marker_update_probes(void)
{
int refcount = 0;
/* Core kernel markers */
marker_update_probe_range(__start___markers,
__stop___markers, probe_module, &refcount);
marker_update_probe_range(__start___markers, __stop___markers);
/* Markers in modules. */
module_update_markers(probe_module, &refcount);
if (probe_module && refcount == 0) {
synchronize_sched();
deferred_sync = 0;
}
module_update_markers();
}
/**
@ -310,33 +632,49 @@ static void marker_update_probes(struct module *probe_module)
* @name: marker name
* @format: format string
* @probe: probe handler
* @private: probe private data
* @probe_private: probe private data
*
* private data must be a valid allocated memory address, or NULL.
* Returns 0 if ok, error value on error.
* The probe address must at least be aligned on the architecture pointer size.
*/
int marker_probe_register(const char *name, const char *format,
marker_probe_func *probe, void *private)
marker_probe_func *probe, void *probe_private)
{
struct marker_entry *entry;
int ret = 0;
struct marker_probe_closure *old;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (entry && entry->refcount) {
ret = -EBUSY;
if (!entry) {
entry = add_marker(name, format);
if (IS_ERR(entry)) {
ret = PTR_ERR(entry);
goto end;
}
}
/*
* If we detect that a call_rcu is pending for this marker,
* make sure it's executed now.
*/
if (entry->rcu_pending)
rcu_barrier();
old = marker_entry_add_probe(entry, probe, probe_private);
if (IS_ERR(old)) {
ret = PTR_ERR(old);
goto end;
}
if (deferred_sync) {
synchronize_sched();
deferred_sync = 0;
}
ret = add_marker(name, format, probe, private);
if (ret)
goto end;
mutex_unlock(&markers_mutex);
marker_update_probes(NULL);
return ret;
marker_update_probes(); /* may update entry */
mutex_lock(&markers_mutex);
entry = get_marker(name);
WARN_ON(!entry);
entry->oldptr = old;
entry->rcu_pending = 1;
/* write rcu_pending before calling the RCU callback */
smp_wmb();
call_rcu(&entry->rcu, free_old_closure);
end:
mutex_unlock(&markers_mutex);
return ret;
@ -346,171 +684,166 @@ EXPORT_SYMBOL_GPL(marker_probe_register);
/**
* marker_probe_unregister - Disconnect a probe from a marker
* @name: marker name
* @probe: probe function pointer
* @probe_private: probe private data
*
* Returns the private data given to marker_probe_register, or an ERR_PTR().
* 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.
*/
void *marker_probe_unregister(const char *name)
int marker_probe_unregister(const char *name,
marker_probe_func *probe, void *probe_private)
{
struct module *probe_module;
struct marker_entry *entry;
void *private;
struct marker_probe_closure *old;
int ret = 0;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (!entry) {
private = ERR_PTR(-ENOENT);
ret = -ENOENT;
goto end;
}
entry->refcount = 0;
/* In what module is the probe handler ? */
probe_module = __module_text_address((unsigned long)entry->probe);
private = remove_marker(name);
deferred_sync = 1;
if (entry->rcu_pending)
rcu_barrier();
old = marker_entry_remove_probe(entry, probe, probe_private);
mutex_unlock(&markers_mutex);
marker_update_probes(probe_module);
return private;
marker_update_probes(); /* may update entry */
mutex_lock(&markers_mutex);
entry = get_marker(name);
entry->oldptr = old;
entry->rcu_pending = 1;
/* write rcu_pending before calling the RCU callback */
smp_wmb();
call_rcu(&entry->rcu, free_old_closure);
remove_marker(name); /* Ignore busy error message */
end:
mutex_unlock(&markers_mutex);
return private;
return ret;
}
EXPORT_SYMBOL_GPL(marker_probe_unregister);
/**
* marker_probe_unregister_private_data - Disconnect a probe from a marker
* @private: probe private data
*
* Unregister a marker by providing the registered private data.
* Returns the private data given to marker_probe_register, or an ERR_PTR().
*/
void *marker_probe_unregister_private_data(void *private)
static struct marker_entry *
get_marker_from_private_data(marker_probe_func *probe, void *probe_private)
{
struct module *probe_module;
struct marker_entry *entry;
unsigned int i;
struct hlist_head *head;
struct hlist_node *node;
struct marker_entry *entry;
int found = 0;
unsigned int i;
mutex_lock(&markers_mutex);
for (i = 0; i < MARKER_TABLE_SIZE; i++) {
head = &marker_table[i];
hlist_for_each_entry(entry, node, head, hlist) {
if (entry->private == private) {
found = 1;
goto iter_end;
if (!entry->ptype) {
if (entry->single.func == probe
&& entry->single.probe_private
== probe_private)
return entry;
} else {
struct marker_probe_closure *closure;
closure = entry->multi;
for (i = 0; closure[i].func; i++) {
if (closure[i].func == probe &&
closure[i].probe_private
== probe_private)
return entry;
}
}
}
}
iter_end:
if (!found) {
private = ERR_PTR(-ENOENT);
return NULL;
}
/**
* marker_probe_unregister_private_data - Disconnect a probe from a marker
* @probe: probe function
* @probe_private: probe private data
*
* Unregister a probe by providing the registered private data.
* Only removes the first marker found in hash table.
* Return 0 on success or error value.
* 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.
*/
int marker_probe_unregister_private_data(marker_probe_func *probe,
void *probe_private)
{
struct marker_entry *entry;
int ret = 0;
struct marker_probe_closure *old;
mutex_lock(&markers_mutex);
entry = get_marker_from_private_data(probe, probe_private);
if (!entry) {
ret = -ENOENT;
goto end;
}
entry->refcount = 0;
/* In what module is the probe handler ? */
probe_module = __module_text_address((unsigned long)entry->probe);
private = remove_marker(entry->name);
deferred_sync = 1;
if (entry->rcu_pending)
rcu_barrier();
old = marker_entry_remove_probe(entry, NULL, probe_private);
mutex_unlock(&markers_mutex);
marker_update_probes(probe_module);
return private;
marker_update_probes(); /* may update entry */
mutex_lock(&markers_mutex);
entry = get_marker_from_private_data(probe, probe_private);
WARN_ON(!entry);
entry->oldptr = old;
entry->rcu_pending = 1;
/* write rcu_pending before calling the RCU callback */
smp_wmb();
call_rcu(&entry->rcu, free_old_closure);
remove_marker(entry->name); /* Ignore busy error message */
end:
mutex_unlock(&markers_mutex);
return private;
return ret;
}
EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
/**
* marker_arm - Arm a marker
* @name: marker name
*
* Activate a marker. It keeps a reference count of the number of
* arming/disarming done.
* Returns 0 if ok, error value on error.
*/
int marker_arm(const char *name)
{
struct marker_entry *entry;
int ret = 0;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (!entry) {
ret = -ENOENT;
goto end;
}
/*
* Only need to update probes when refcount passes from 0 to 1.
*/
if (entry->refcount++)
goto end;
end:
mutex_unlock(&markers_mutex);
marker_update_probes(NULL);
return ret;
}
EXPORT_SYMBOL_GPL(marker_arm);
/**
* marker_disarm - Disarm a marker
* @name: marker name
*
* Disarm a marker. It keeps a reference count of the number of arming/disarming
* done.
* Returns 0 if ok, error value on error.
*/
int marker_disarm(const char *name)
{
struct marker_entry *entry;
int ret = 0;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (!entry) {
ret = -ENOENT;
goto end;
}
/*
* Only permit decrement refcount if higher than 0.
* Do probe update only on 1 -> 0 transition.
*/
if (entry->refcount) {
if (--entry->refcount)
goto end;
} else {
ret = -EPERM;
goto end;
}
end:
mutex_unlock(&markers_mutex);
marker_update_probes(NULL);
return ret;
}
EXPORT_SYMBOL_GPL(marker_disarm);
/**
* marker_get_private_data - Get a marker's probe private data
* @name: marker name
* @probe: probe to match
* @num: get the nth matching probe's private data
*
* Returns the nth private data pointer (starting from 0) matching, or an
* ERR_PTR.
* Returns the private data pointer, or an ERR_PTR.
* The private data pointer should _only_ be dereferenced if the caller is the
* owner of the data, or its content could vanish. This is mostly used to
* confirm that a caller is the owner of a registered probe.
*/
void *marker_get_private_data(const char *name)
void *marker_get_private_data(const char *name, marker_probe_func *probe,
int num)
{
struct hlist_head *head;
struct hlist_node *node;
struct marker_entry *e;
size_t name_len = strlen(name) + 1;
u32 hash = jhash(name, name_len-1, 0);
int found = 0;
int i;
head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
hlist_for_each_entry(e, node, head, hlist) {
if (!strcmp(name, e->name)) {
found = 1;
return e->private;
if (!e->ptype) {
if (num == 0 && e->single.func == probe)
return e->single.probe_private;
else
break;
} else {
struct marker_probe_closure *closure;
int match = 0;
closure = e->multi;
for (i = 0; closure[i].func; i++) {
if (closure[i].func != probe)
continue;
if (match++ == num)
return closure[i].probe_private;
}
}
}
}
return ERR_PTR(-ENOENT);

7
kernel/module.c
View file

@ -2038,7 +2038,7 @@ static struct module *load_module(void __user *umod,
#ifdef CONFIG_MARKERS
if (!mod->taints)
marker_update_probe_range(mod->markers,
mod->markers + mod->num_markers, NULL, NULL);
mod->markers + mod->num_markers);
#endif
err = module_finalize(hdr, sechdrs, mod);
if (err < 0)
@ -2564,7 +2564,7 @@ EXPORT_SYMBOL(struct_module);
#endif
#ifdef CONFIG_MARKERS
void module_update_markers(struct module *probe_module, int *refcount)
void module_update_markers(void)
{
struct module *mod;
@ -2572,8 +2572,7 @@ void module_update_markers(struct module *probe_module, int *refcount)
list_for_each_entry(mod, &modules, list)
if (!mod->taints)
marker_update_probe_range(mod->markers,
mod->markers + mod->num_markers,
probe_module, refcount);
mod->markers + mod->num_markers);
mutex_unlock(&module_mutex);
}
#endif

25
samples/markers/probe-example.c
View file

@ -20,31 +20,27 @@ struct probe_data {
marker_probe_func *probe_func;
};
void probe_subsystem_event(const struct marker *mdata, void *private,
const char *format, ...)
void probe_subsystem_event(void *probe_data, void *call_data,
const char *format, va_list *args)
{
va_list ap;
/* Declare args */
unsigned int value;
const char *mystr;
/* Assign args */
va_start(ap, format);
value = va_arg(ap, typeof(value));
mystr = va_arg(ap, typeof(mystr));
value = va_arg(*args, typeof(value));
mystr = va_arg(*args, typeof(mystr));
/* Call printk */
printk(KERN_DEBUG "Value %u, string %s\n", value, mystr);
printk(KERN_INFO "Value %u, string %s\n", value, mystr);
/* or count, check rights, serialize data in a buffer */
va_end(ap);
}
atomic_t eventb_count = ATOMIC_INIT(0);
void probe_subsystem_eventb(const struct marker *mdata, void *private,
const char *format, ...)
void probe_subsystem_eventb(void *probe_data, void *call_data,
const char *format, va_list *args)
{
/* Increment counter */
atomic_inc(&eventb_count);
@ -72,10 +68,6 @@ static int __init probe_init(void)
if (result)
printk(KERN_INFO "Unable to register probe %s\n",
probe_array[i].name);
result = marker_arm(probe_array[i].name);
if (result)
printk(KERN_INFO "Unable to arm probe %s\n",
probe_array[i].name);
}
return 0;
}
@ -85,7 +77,8 @@ static void __exit probe_fini(void)
int i;
for (i = 0; i < ARRAY_SIZE(probe_array); i++)
marker_probe_unregister(probe_array[i].name);
marker_probe_unregister(probe_array[i].name,
probe_array[i].probe_func, &probe_array[i]);
printk(KERN_INFO "Number of event b : %u\n",
atomic_read(&eventb_count));
}