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Date: Mon, 01 Jul 2013 15:22:13 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "zhangwei(Jovi)" <jovi.zhangwei@...wei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Oleg Nesterov <oleg@...hat.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] tracing/uprobes: Support ftrace_event_file base
multibuffer
On Sat, 2013-06-29 at 15:51 +0800, zhangwei(Jovi) wrote:
> [v3->v4]:
> 1. use "bool enabled = is_trace_uprobe_enabled(tu);", suggested by Oleg.
> 2. use list_add_tail_rcu instead of list_add_rcu, suggested by Masami.
> 3. fix the error handling in probe_event_enable, found by Srikar.
Is this the final patch?
Masami, can you give your reviewed by (Oleg and Srikar, feel free to add
your tags either).
Also, the origin was a two patch set. Is the second patch needed?
Thanks,
-- Steve
>
> -------------------
>
> Support multi-buffer on uprobe-based dynamic events by
> using ftrace_event_file.
>
> This patch is based kprobe-based dynamic events multibuffer
> support work initially, commited by Masami(commit 41a7dd420c),
> but revised as below:
>
> Oleg changed the kprobe-based multibuffer design from
> array-pointers of ftrace_event_file into simple list,
> so this patch also change to the list degisn.
>
> rcu_read_lock/unlock added into uprobe_trace_func/uretprobe_trace_func,
> to synchronize with ftrace_event_file list add and delete.
>
> Even though we allow multi-uprobes instances now,
> but TP_FLAG_PROFILE/TP_FLAG_TRACE are still mutually exclusive
> in probe_event_enable currently, this means we cannot allow
> one user is using uprobe-tracer, and another user is using
> perf-probe on same uprobe concurrently.
> (Perhaps this will be fix in future, kprobe dont't have this
> limitation now)
>
> 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 | 123 +++++++++++++++++++++++++++++++++++--------
> 1 file changed, 101 insertions(+), 22 deletions(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 32494fb0..760d4ed 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 list_head files;
> struct trace_uprobe_filter filter;
> struct uprobe_consumer consumer;
> struct inode *inode;
> @@ -65,6 +66,11 @@ struct trace_uprobe {
> struct probe_arg args[];
> };
>
> +struct event_file_link {
> + struct ftrace_event_file *file;
> + struct list_head list;
> +};
> +
> #define SIZEOF_TRACE_UPROBE(n) \
> (offsetof(struct trace_uprobe, args) + \
> (sizeof(struct probe_arg) * (n)))
> @@ -124,6 +130,7 @@ alloc_trace_uprobe(const char *group, const char *event, int nargs, bool is_ret)
> goto error;
>
> INIT_LIST_HEAD(&tu->list);
> + INIT_LIST_HEAD(&tu->files);
> tu->consumer.handler = uprobe_dispatcher;
> if (is_ret)
> tu->consumer.ret_handler = uretprobe_dispatcher;
> @@ -511,7 +518,8 @@ 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;
> @@ -520,9 +528,12 @@ 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);
> +
> 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;
>
> @@ -546,15 +557,28 @@ 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 event_file_link *link;
> +
> + if (is_ret_probe(tu))
> + return 0;
> +
> + rcu_read_lock();
> + list_for_each_entry(link, &tu->files, list)
> + uprobe_trace_print(tu, 0, regs, link->file);
> + rcu_read_unlock();
> +
> 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 event_file_link *link;
> +
> + rcu_read_lock();
> + list_for_each_entry(link, &tu->files, list)
> + uprobe_trace_print(tu, func, regs, link->file);
> + rcu_read_unlock();
> }
>
> /* Event entry printers */
> @@ -605,33 +629,87 @@ 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)
> {
> + bool enabled = is_trace_uprobe_enabled(tu);
> + struct event_file_link *link;
> int ret = 0;
>
> - if (is_trace_uprobe_enabled(tu))
> - return -EINTR;
> + if (file) {
> + if (tu->flags & TP_FLAG_PROFILE)
> + return -EINTR;
> +
> + link = kmalloc(sizeof(*link), GFP_KERNEL);
> + if (!link)
> + return -ENOMEM;
> +
> + link->file = file;
> + list_add_tail_rcu(&link->list, &tu->files);
> +
> + tu->flags |= TP_FLAG_TRACE;
> + } else {
> + if (tu->flags & TP_FLAG_TRACE)
> + return -EINTR;
> +
> + 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;
> + /* we cannot call uprobe_register twice for same tu */
> + if (!enabled) {
> + tu->consumer.filter = filter;
> + ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
> + }
> +
> + if (ret) {
> + if (file) {
> + list_del_rcu(&link->list);
> + kfree(link);
> + tu->flags &= ~TP_FLAG_TRACE;
> + } else
> + tu->flags &= ~TP_FLAG_PROFILE;
> + }
>
> return ret;
> }
>
> -static void probe_event_disable(struct trace_uprobe *tu, int flag)
> +static struct event_file_link *
> +find_event_file_link(struct trace_uprobe *tu, struct ftrace_event_file *file)
> {
> - if (!is_trace_uprobe_enabled(tu))
> - return;
> + struct event_file_link *link;
> +
> + list_for_each_entry(link, &tu->files, list)
> + if (link->file == file)
> + return link;
> +
> + return NULL;
> +}
> +
> +static void
> +probe_event_disable(struct trace_uprobe *tu, struct ftrace_event_file *file)
> +{
> + if (file) {
> + struct event_file_link *link;
> +
> + link = find_event_file_link(tu, file);
> + if (!link)
> + return;
> +
> + list_del_rcu(&link->list);
> + /* synchronize with uprobe_trace_func/uretprobe_trace_func */
> + synchronize_sched();
> + kfree(link);
> +
> + if (!list_empty(&tu->files))
> + return;
> + }
>
> WARN_ON(!uprobe_filter_is_empty(&tu->filter));
>
> uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
> - tu->flags &= ~flag;
> + tu->flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;
> }
>
> static int uprobe_event_define_fields(struct ftrace_event_call *event_call)
> @@ -867,21 +945,22 @@ 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:
--
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