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Message-ID: <51BB18EB.9080307@hitachi.com>
Date: Fri, 14 Jun 2013 22:21:47 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: "zhangwei(Jovi)" <jovi.zhangwei@...wei.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>,
Oleg Nesterov <oleg@...hat.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>
Subject: Re: [PATCH] tracing/uprobes: Support ftrace_event_file base multibuffer
(2013/06/14 10:44), zhangwei(Jovi) wrote:
> Support multi-buffer on uprobe-based dynamic events by
> using ftrace_event_file.
>
> The code change is based on kprobe-based dynamic events
> multibuffer support work commited by Masami(commit 41a7dd420c)
I'm not so sure that rcu_dereference_raw() can ensure the safety
of accessing pointer in uprobe handler. ( since kprobes disables
irq and preempt, it could use rcu.)
Srikar, Oleg, could you check that?
Thank you,
>
> Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@...wei.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> ---
> kernel/trace/trace_uprobe.c | 183 +++++++++++++++++++++++++++++++++++++------
> 1 file changed, 161 insertions(+), 22 deletions(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index d5d0cd3..31f08d6 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -53,6 +53,7 @@ struct trace_uprobe {
> struct list_head list;
> struct ftrace_event_class class;
> struct ftrace_event_call call;
> + struct ftrace_event_file * __rcu *files;
> struct trace_uprobe_filter filter;
> struct uprobe_consumer consumer;
> struct inode *inode;
> @@ -513,7 +514,8 @@ static const struct file_operations uprobe_profile_ops = {
> };
>
> static void uprobe_trace_print(struct trace_uprobe *tu,
> - unsigned long func, struct pt_regs *regs)
> + unsigned long func, struct pt_regs *regs,
> + struct ftrace_event_file *ftrace_file)
> {
> struct uprobe_trace_entry_head *entry;
> struct ring_buffer_event *event;
> @@ -522,9 +524,15 @@ static void uprobe_trace_print(struct trace_uprobe *tu,
> int size, i;
> struct ftrace_event_call *call = &tu->call;
>
> + WARN_ON(call != ftrace_file->event_call);
> +
> + if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &ftrace_file->flags))
> + return;
> +
> size = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
> - event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
> - size + tu->size, 0, 0);
> + event = trace_event_buffer_lock_reserve(&buffer, ftrace_file,
> + call->event.type,
> + size + tu->size, 0, 0);
> if (!event)
> return;
>
> @@ -548,15 +556,35 @@ static void uprobe_trace_print(struct trace_uprobe *tu,
> /* uprobe handler */
> static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
> {
> - if (!is_ret_probe(tu))
> - uprobe_trace_print(tu, 0, regs);
> + struct ftrace_event_file **file;
> +
> + if (is_ret_probe(tu))
> + return 0;
> +
> + file = rcu_dereference_raw(tu->files);
> + if (unlikely(!file))
> + return 0;
> +
> + while (*file) {
> + uprobe_trace_print(tu, 0, regs, *file);
> + file++;
> + }
> +
> return 0;
> }
>
> static void uretprobe_trace_func(struct trace_uprobe *tu, unsigned long func,
> struct pt_regs *regs)
> {
> - uprobe_trace_print(tu, func, regs);
> + struct ftrace_event_file **file = rcu_dereference_raw(tu->files);
> +
> + if (unlikely(!file))
> + return;
> +
> + while (*file) {
> + uprobe_trace_print(tu, func, regs, *file);
> + file++;
> + }
> }
>
> /* Event entry printers */
> @@ -597,6 +625,26 @@ partial:
> return TRACE_TYPE_PARTIAL_LINE;
> }
>
> +
> +static int trace_uprobe_nr_files(struct trace_uprobe *tu)
> +{
> + struct ftrace_event_file **file;
> + int ret = 0;
> +
> + /*
> + * Since all tu->files updater is protected by uprobe_enable_lock,
> + * we don't need to lock an rcu_read_lock.
> + */
> + file = rcu_dereference_raw(tu->files);
> + if (file)
> + while (*(file++))
> + ret++;
> +
> + return ret;
> +}
> +
> +static DEFINE_MUTEX(uprobe_enable_lock);
> +
> static inline bool is_trace_uprobe_enabled(struct trace_uprobe *tu)
> {
> return tu->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE);
> @@ -607,33 +655,123 @@ typedef bool (*filter_func_t)(struct uprobe_consumer *self,
> struct mm_struct *mm);
>
> static int
> -probe_event_enable(struct trace_uprobe *tu, int flag, filter_func_t filter)
> +probe_event_enable(struct trace_uprobe *tu, struct ftrace_event_file *file,
> + filter_func_t filter)
> {
> + int enabled = 0;
> int ret = 0;
>
> + mutex_lock(&uprobe_enable_lock);
> +
> if (is_trace_uprobe_enabled(tu))
> - return -EINTR;
> + enabled = 1;
> +
> + if (file) {
> + struct ftrace_event_file **new, **old;
> + int n = trace_uprobe_nr_files(tu);
> +
> + old = rcu_dereference_raw(tu->files);
> + /* 1 is for new one and 1 is for stopper */
> + new = kzalloc((n + 2) * sizeof(struct ftrace_event_file *),
> + GFP_KERNEL);
> + if (!new) {
> + ret = -ENOMEM;
> + goto out_unlock;
> + }
> + memcpy(new, old, n * sizeof(struct ftrace_event_file *));
> + new[n] = file;
> + /* The last one keeps a NULL */
> +
> + rcu_assign_pointer(tu->files, new);
> + tu->flags |= TP_FLAG_TRACE;
> +
> + if (old) {
> + /* Make sure the probe is done with old files */
> + synchronize_sched();
> + kfree(old);
> + }
> + } else
> + tu->flags |= TP_FLAG_PROFILE;
>
> WARN_ON(!uprobe_filter_is_empty(&tu->filter));
>
> - tu->flags |= flag;
> - tu->consumer.filter = filter;
> - ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
> - if (ret)
> - tu->flags &= ~flag;
> + if (!enabled) {
> + tu->consumer.filter = filter;
> + ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
> + if (ret)
> + tu->flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;
> + }
>
> + out_unlock:
> + mutex_unlock(&uprobe_enable_lock);
> return ret;
> }
>
> -static void probe_event_disable(struct trace_uprobe *tu, int flag)
> +static int
> +trace_uprobe_file_index(struct trace_uprobe *tu, struct ftrace_event_file *file)
> {
> - if (!is_trace_uprobe_enabled(tu))
> - return;
> + struct ftrace_event_file **files;
> + int i;
> +
> + /*
> + * Since all tu->files updater is protected by uprobe_enable_lock,
> + * we don't need to lock an rcu_read_lock.
> + */
> + files = rcu_dereference_raw(tu->files);
> + if (files) {
> + for (i = 0; files[i]; i++)
> + if (files[i] == file)
> + return i;
> + }
> +
> + return -1;
> +}
> +
> +static void
> +probe_event_disable(struct trace_uprobe *tu, struct ftrace_event_file *file)
> +{
> + mutex_lock(&uprobe_enable_lock);
> +
> + if (file) {
> + struct ftrace_event_file **new, **old;
> + int n = trace_uprobe_nr_files(tu);
> + int i, j;
> +
> + old = rcu_dereference_raw(tu->files);
> + if (n == 0 || trace_uprobe_file_index(tu, file) < 0)
> + goto out_unlock;
> +
> + if (n == 1) { /* Remove the last file */
> + tu->flags &= ~TP_FLAG_TRACE;
> + new = NULL;
> + } else {
> + new = kzalloc(n * sizeof(struct ftrace_event_file *),
> + GFP_KERNEL);
> + if (!new)
> + goto out_unlock;
> +
> + /* 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(tu->files, new);
> +
> + /* Make sure the probe is done with old files */
> + synchronize_sched();
> + kfree(old);
> + } else
> + tu->flags &= ~TP_FLAG_PROFILE;
> +
>
> WARN_ON(!uprobe_filter_is_empty(&tu->filter));
>
> - uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
> - tu->flags &= ~flag;
> + if (!is_trace_uprobe_enabled(tu))
> + uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
> +
> + out_unlock:
> + mutex_unlock(&uprobe_enable_lock);
> }
>
> static int uprobe_event_define_fields(struct ftrace_event_call *event_call)
> @@ -869,21 +1007,22 @@ static
> int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, void *data)
> {
> struct trace_uprobe *tu = event->data;
> + struct ftrace_event_file *file = data;
>
> switch (type) {
> case TRACE_REG_REGISTER:
> - return probe_event_enable(tu, TP_FLAG_TRACE, NULL);
> + return probe_event_enable(tu, file, NULL);
>
> case TRACE_REG_UNREGISTER:
> - probe_event_disable(tu, TP_FLAG_TRACE);
> + probe_event_disable(tu, file);
> return 0;
>
> #ifdef CONFIG_PERF_EVENTS
> case TRACE_REG_PERF_REGISTER:
> - return probe_event_enable(tu, TP_FLAG_PROFILE, uprobe_perf_filter);
> + return probe_event_enable(tu, NULL, uprobe_perf_filter);
>
> case TRACE_REG_PERF_UNREGISTER:
> - probe_event_disable(tu, TP_FLAG_PROFILE);
> + probe_event_disable(tu, NULL);
> return 0;
>
> case TRACE_REG_PERF_OPEN:
>
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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