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tracing/kprobes: Turn trace_probe->files into list_head

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I think that "ftrace_event_file *trace_probe[]" complicates the
code for no reason, turn it into list_head to simplify the code.
enable_trace_probe() no longer needs synchronize_sched().

This needs the extra sizeof(list_head) memory for every attached
ftrace_event_file, hopefully not a problem in this case.

Link: http://lkml.kernel.org/r/20130620173814.GA13165@redhat.com

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Oleg Nesterov
2013-06-20 19:38:14 +02:00
committed by Steven Rostedt
parent 3baa5e4cf2
commit b04d52e368
1 changed files with 37 additions and 101 deletions
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138
kernel/trace/trace_kprobe.c
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@@ -35,12 +35,17 @@ struct trace_probe {
const char *symbol; /* symbol name */ const char *symbol; /* symbol name */
struct ftrace_event_class class; struct ftrace_event_class class;
struct ftrace_event_call call; struct ftrace_event_call call;
struct ftrace_event_file * __rcu *files; struct list_head files;
ssize_t size; /* trace entry size */ ssize_t size; /* trace entry size */
unsigned int nr_args; unsigned int nr_args;
struct probe_arg args[]; struct probe_arg args[];
}; };
struct event_file_link {
struct ftrace_event_file *file;
struct list_head list;
};
#define SIZEOF_TRACE_PROBE(n) \ #define SIZEOF_TRACE_PROBE(n) \
(offsetof(struct trace_probe, args) + \ (offsetof(struct trace_probe, args) + \
(sizeof(struct probe_arg) * (n))) (sizeof(struct probe_arg) * (n)))
@@ -150,6 +155,7 @@ static struct trace_probe *alloc_trace_probe(const char *group,
goto error; goto error;
INIT_LIST_HEAD(&tp->list); INIT_LIST_HEAD(&tp->list);
INIT_LIST_HEAD(&tp->files);
return tp; return tp;
error: error:
kfree(tp->call.name); kfree(tp->call.name);
@@ -183,22 +189,6 @@ static struct trace_probe *find_trace_probe(const char *event,
return NULL; return NULL;
} }
/*
* This and enable_trace_probe/disable_trace_probe rely on event_mutex
* held by the caller, __ftrace_set_clr_event().
*/
static int trace_probe_nr_files(struct trace_probe *tp)
{
struct ftrace_event_file **file = rcu_dereference_raw(tp->files);
int ret = 0;
if (file)
while (*(file++))
ret++;
return ret;
}
/* /*
* Enable trace_probe * Enable trace_probe
* if the file is NULL, enable "perf" handler, or enable "trace" handler. * if the file is NULL, enable "perf" handler, or enable "trace" handler.
@@ -209,29 +199,18 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
int ret = 0; int ret = 0;
if (file) { if (file) {
struct ftrace_event_file **new, **old; struct event_file_link *link;
int n = trace_probe_nr_files(tp);
old = rcu_dereference_raw(tp->files); link = kmalloc(sizeof(*link), GFP_KERNEL);
/* 1 is for new one and 1 is for stopper */ if (!link) {
new = kzalloc((n + 2) * sizeof(struct ftrace_event_file *),
GFP_KERNEL);
if (!new) {
ret = -ENOMEM; ret = -ENOMEM;
goto out; goto out;
} }
memcpy(new, old, n * sizeof(struct ftrace_event_file *));
new[n] = file;
/* The last one keeps a NULL */
rcu_assign_pointer(tp->files, new); link->file = file;
list_add_tail_rcu(&link->list, &tp->files);
tp->flags |= TP_FLAG_TRACE; tp->flags |= TP_FLAG_TRACE;
if (old) {
/* Make sure the probe is done with old files */
synchronize_sched();
kfree(old);
}
} else } else
tp->flags |= TP_FLAG_PROFILE; tp->flags |= TP_FLAG_PROFILE;
@@ -245,24 +224,16 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
return ret; return ret;
} }
static int static struct event_file_link *
trace_probe_file_index(struct trace_probe *tp, struct ftrace_event_file *file) find_event_file_link(struct trace_probe *tp, struct ftrace_event_file *file)
{ {
struct ftrace_event_file **files; struct event_file_link *link;
int i;
/* list_for_each_entry(link, &tp->files, list)
* Since all tp->files updater is protected by probe_enable_lock, if (link->file == file)
* we don't need to lock an rcu_read_lock. return link;
*/
files = rcu_dereference_raw(tp->files);
if (files) {
for (i = 0; files[i]; i++)
if (files[i] == file)
return i;
}
return -1; return NULL;
} }
/* /*
@@ -275,38 +246,23 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
int ret = 0; int ret = 0;
if (file) { if (file) {
struct ftrace_event_file **new, **old; struct event_file_link *link;
int n = trace_probe_nr_files(tp);
int i, j;
old = rcu_dereference_raw(tp->files); link = find_event_file_link(tp, file);
if (n == 0 || trace_probe_file_index(tp, file) < 0) { if (!link) {
ret = -EINVAL; ret = -EINVAL;
goto out; goto out;
} }
if (n == 1) { /* Remove the last file */ list_del_rcu(&link->list);
tp->flags &= ~TP_FLAG_TRACE; /* synchronize with kprobe_trace_func/kretprobe_trace_func */
new = NULL;
} else {
new = kzalloc(n * sizeof(struct ftrace_event_file *),
GFP_KERNEL);
if (!new) {
ret = -ENOMEM;
goto out;
}
/* This copy & check loop copies the NULL stopper too */
for (i = 0, j = 0; j < n && i < n + 1; i++)
if (old[i] != file)
new[j++] = old[i];
}
rcu_assign_pointer(tp->files, new);
/* Make sure the probe is done with old files */
synchronize_sched(); synchronize_sched();
kfree(old); kfree(link);
if (!list_empty(&tp->files))
goto out;
tp->flags &= ~TP_FLAG_TRACE;
} else } else
tp->flags &= ~TP_FLAG_PROFILE; tp->flags &= ~TP_FLAG_PROFILE;
@@ -871,20 +827,10 @@ __kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs,
static __kprobes void static __kprobes void
kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs) kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs)
{ {
/* struct event_file_link *link;
* Note: preempt is already disabled around the kprobe handler.
* However, we still need an smp_read_barrier_depends() corresponding
* to smp_wmb() in rcu_assign_pointer() to access the pointer.
*/
struct ftrace_event_file **file = rcu_dereference_raw(tp->files);
if (unlikely(!file)) list_for_each_entry_rcu(link, &tp->files, list)
return; __kprobe_trace_func(tp, regs, link->file);
while (*file) {
__kprobe_trace_func(tp, regs, *file);
file++;
}
} }
/* Kretprobe handler */ /* Kretprobe handler */
@@ -931,20 +877,10 @@ static __kprobes void
kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri, kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri,
struct pt_regs *regs) struct pt_regs *regs)
{ {
/* struct event_file_link *link;
* Note: preempt is already disabled around the kprobe handler.
* However, we still need an smp_read_barrier_depends() corresponding
* to smp_wmb() in rcu_assign_pointer() to access the pointer.
*/
struct ftrace_event_file **file = rcu_dereference_raw(tp->files);
if (unlikely(!file)) list_for_each_entry_rcu(link, &tp->files, list)
return; __kretprobe_trace_func(tp, ri, regs, link->file);
while (*file) {
__kretprobe_trace_func(tp, ri, regs, *file);
file++;
}
} }
/* Event entry printers */ /* Event entry printers */