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Date: Fri, 28 Jun 2013 18:59:04 +0800
From: "zhangwei(Jovi)" <jovi.zhangwei@...wei.com>
To: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
CC: Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Oleg Nesterov <oleg@...hat.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2 v3] tracing/uprobes: Support ftrace_event_file base
multibuffer
On 2013/6/27 20:12, Srikar Dronamraju wrote:
> * zhangwei(Jovi) <jovi.zhangwei@...wei.com> [2013-06-25 11:30:20]:
>
>> 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 | 118 +++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 97 insertions(+), 21 deletions(-)
>>
>> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
>> index 32494fb0..dbbb4a9 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 +629,84 @@ 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;
>>
>> + /* we cannot call uprobe_register twice for same tu */
>> if (is_trace_uprobe_enabled(tu))
>> - return -EINTR;
>> + enabled = 1;
>> +
>> + if (file) {
>> + struct event_file_link *link;
>> +
>> + if (tu->flags & TP_FLAG_PROFILE)
>> + return -EINTR;
>> +
>> + link = kmalloc(sizeof(*link), GFP_KERNEL);
>> + if (!link)
>> + return -ENOMEM;
>> +
>> + link->file = file;
>> + list_add_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;
>> + 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;
>
> Dont we need to free link here? or where does the link that got
> allocated freed?
>
> Think the list of files also needs to be cleaned up. No?
>
Thanks for review, I will update it in next series.
jovi
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