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Message-ID: <20130616172152.GA8543@redhat.com>
Date: Sun, 16 Jun 2013 19:21:52 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Steven Rostedt <rostedt@...dmis.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] tracing/kprobes: Turn trace_probe->files into list_head
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.
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
kernel/trace/trace_kprobe.c | 138 ++++++++++++-------------------------------
1 files changed, 37 insertions(+), 101 deletions(-)
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 5a73de0..b95f683 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -35,12 +35,17 @@ struct trace_probe {
const char *symbol; /* symbol name */
struct ftrace_event_class class;
struct ftrace_event_call call;
- struct ftrace_event_file * __rcu *files;
+ struct list_head files;
ssize_t size; /* trace entry size */
unsigned int nr_args;
struct probe_arg args[];
};
+struct event_file_link {
+ struct ftrace_event_file *file;
+ struct list_head list;
+};
+
#define SIZEOF_TRACE_PROBE(n) \
(offsetof(struct trace_probe, args) + \
(sizeof(struct probe_arg) * (n)))
@@ -150,6 +155,7 @@ static struct trace_probe *alloc_trace_probe(const char *group,
goto error;
INIT_LIST_HEAD(&tp->list);
+ INIT_LIST_HEAD(&tp->files);
return tp;
error:
kfree(tp->call.name);
@@ -184,22 +190,6 @@ static struct trace_probe *find_trace_probe(const char *event,
}
/*
- * 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
* 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;
if (file) {
- struct ftrace_event_file **new, **old;
- int n = trace_probe_nr_files(tp);
-
- old = rcu_dereference_raw(tp->files);
- /* 1 is for new one and 1 is for stopper */
- new = kzalloc((n + 2) * sizeof(struct ftrace_event_file *),
- GFP_KERNEL);
- if (!new) {
+ struct event_file_link *link;
+
+ link = kmalloc(sizeof(*link), GFP_KERNEL);
+ if (!link) {
ret = -ENOMEM;
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);
- tp->flags |= TP_FLAG_TRACE;
+ link->file = file;
+ list_add_rcu(&link->list, &tp->files);
- if (old) {
- /* Make sure the probe is done with old files */
- synchronize_sched();
- kfree(old);
- }
+ tp->flags |= TP_FLAG_TRACE;
} else
tp->flags |= TP_FLAG_PROFILE;
@@ -246,24 +225,16 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
return ret;
}
-static int
-trace_probe_file_index(struct trace_probe *tp, struct ftrace_event_file *file)
+static struct event_file_link *
+find_event_file_link(struct trace_probe *tp, struct ftrace_event_file *file)
{
- struct ftrace_event_file **files;
- int i;
+ struct event_file_link *link;
- /*
- * Since all tp->files updater is protected by probe_enable_lock,
- * we don't need to lock an rcu_read_lock.
- */
- files = rcu_dereference_raw(tp->files);
- if (files) {
- for (i = 0; files[i]; i++)
- if (files[i] == file)
- return i;
- }
+ list_for_each_entry(link, &tp->files, list)
+ if (link->file == file)
+ return link;
- return -1;
+ return NULL;
}
/*
@@ -276,38 +247,23 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
int ret = 0;
if (file) {
- struct ftrace_event_file **new, **old;
- int n = trace_probe_nr_files(tp);
- int i, j;
+ struct event_file_link *link;
- old = rcu_dereference_raw(tp->files);
- if (n == 0 || trace_probe_file_index(tp, file) < 0) {
+ link = find_event_file_link(tp, file);
+ if (!link) {
ret = -EINVAL;
goto out;
}
- if (n == 1) { /* Remove the last file */
- tp->flags &= ~TP_FLAG_TRACE;
- 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];
- }
+ list_del_rcu(&link->list);
+ /* synchronize with kprobe_trace_func/kretprobe_trace_func */
+ synchronize_sched();
+ kfree(link);
- rcu_assign_pointer(tp->files, new);
+ if (!list_empty(&tp->files))
+ goto out;
- /* Make sure the probe is done with old files */
- synchronize_sched();
- kfree(old);
+ tp->flags &= ~TP_FLAG_TRACE;
} else
tp->flags &= ~TP_FLAG_PROFILE;
@@ -872,20 +828,10 @@ __kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs,
static __kprobes void
kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs)
{
- /*
- * 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))
- return;
+ struct event_file_link *link;
- while (*file) {
- __kprobe_trace_func(tp, regs, *file);
- file++;
- }
+ list_for_each_entry_rcu(link, &tp->files, list)
+ __kprobe_trace_func(tp, regs, link->file);
}
/* Kretprobe handler */
@@ -932,20 +878,10 @@ static __kprobes void
kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri,
struct pt_regs *regs)
{
- /*
- * 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))
- return;
+ struct event_file_link *link;
- while (*file) {
- __kretprobe_trace_func(tp, ri, regs, *file);
- file++;
- }
+ list_for_each_entry_rcu(link, &tp->files, list)
+ __kretprobe_trace_func(tp, ri, regs, link->file);
}
/* Event entry printers */
--
1.5.5.1
--
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