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Date: Thu, 4 Dec 2008 11:31:40 +0100
From: "Frédéric Weisbecker" <fweisbec@...il.com>
To: "Steven Rostedt" <rostedt@...dmis.org>
Cc: "Ingo Molnar" <mingo@...e.hu>,
"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
"Linux Kernel" <linux-kernel@...r.kernel.org>,
"Tim Bird" <tim.bird@...sony.com>, "Pekka Paalanen" <pq@....fi>
Subject: Re: [PATCH] tracing/function-graph-tracer: handle ftrace_printk entries
2008/12/4 Steven Rostedt <rostedt@...dmis.org>:
> I wonder if we should add a new flag called "NOTRACE" to the new
> current->trace flags. When set, tracing is stopped for the task. Then we
> can still use spinlock here. We only want to use raw if the tracing will
> cause lockdep to fail, not just to prevent traces.
>
> We could do something like:
>
> pause_trace(current); /* sets the "notrace" flag */
>
> unpause_trace(current); /* clears the "notrace" flag */
You're right, I took a kind of insane approach.
I think such a flag would be useful here and probably for further uses too.
I will send a patch.
>>
>> len = min(len, TRACE_BUF_SIZE-1);
>> @@ -3601,13 +3609,15 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
>> tracing_generic_entry_update(&entry->ent, flags, pc);
>> entry->ent.type = TRACE_PRINT;
>> entry->ip = ip;
>> + entry->depth = depth;
>>
>> memcpy(&entry->buf, trace_buf, len);
>> entry->buf[len] = 0;
>> ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
>>
>> out_unlock:
>> - spin_unlock_irqrestore(&trace_buf_lock, flags);
>> + __raw_spin_unlock(&trace_buf_lock);
>> + local_irq_restore(flags);
>>
>> out:
>> preempt_enable_notrace();
>> @@ -3625,7 +3635,13 @@ int __ftrace_printk(unsigned long ip, const char *fmt, ...)
>> return 0;
>>
>> va_start(ap, fmt);
>> - ret = trace_vprintk(ip, fmt, ap);
>> +
>> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
>> + ret = trace_vprintk(ip, current->curr_ret_stack, fmt, ap);
>> +#else
>> + ret = trace_vprintk(ip, -1, fmt, ap);
>> +#endif
>
> Could you make a macro task_curr_ret_stack(task) and in the ftrace header
> file have:
>
> #ifdef CONFIG_FUNCTION_GRAPH_TRACER
> static inline int task_curr_ret_stack(struct task_struct *task)
> {
> return task->curr_ret_stack;
> }
> #else
> static inline int task_curr_ret_stack(struct task_struct *task)
> {
> return -1;
> }
> #endif
>
> And then you could get rid of the #ifdefs in the code and just use:
>
> ret = trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
>
Ok.
>> +
>> va_end(ap);
>> return ret;
>> }
>> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
>> index 0565ae9..fce9889 100644
>> --- a/kernel/trace/trace.h
>> +++ b/kernel/trace/trace.h
>> @@ -117,6 +117,7 @@ struct userstack_entry {
>> struct print_entry {
>> struct trace_entry ent;
>> unsigned long ip;
>> + int depth;
>> char buf[];
>> };
>>
>> @@ -498,7 +499,8 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip,
>> extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
>> size_t cnt);
>> extern long ns2usecs(cycle_t nsec);
>> -extern int trace_vprintk(unsigned long ip, const char *fmt, va_list args);
>> +extern int
>> +trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args);
>>
>> extern unsigned long trace_flags;
>>
>> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
>> index c66578f..32b7fb9 100644
>> --- a/kernel/trace/trace_functions_graph.c
>> +++ b/kernel/trace/trace_functions_graph.c
>> @@ -173,7 +173,7 @@ verif_pid(struct trace_seq *s, pid_t pid, int cpu)
>>
>> */
>> ret = trace_seq_printf(s,
>> - "\n ------------------------------------------\n |");
>> + " ------------------------------------------\n");
>> if (!ret)
>> TRACE_TYPE_PARTIAL_LINE;
>>
>> @@ -477,6 +477,71 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
>> return TRACE_TYPE_HANDLED;
>> }
>>
>> +static enum print_line_t
>> +print_graph_comment(struct print_entry *trace, struct trace_seq *s,
>> + struct trace_entry *ent, struct trace_iterator *iter)
>> +{
>> + int i;
>> + int ret;
>> +
>> + /* Pid */
>> + if (verif_pid(s, ent->pid, iter->cpu) == TRACE_TYPE_PARTIAL_LINE)
>> + return TRACE_TYPE_PARTIAL_LINE;
>> +
>> + /* Cpu */
>> + if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU) {
>> + ret = print_graph_cpu(s, iter->cpu);
>> + if (ret == TRACE_TYPE_PARTIAL_LINE)
>> + return TRACE_TYPE_PARTIAL_LINE;
>> + }
>> +
>> + /* Proc */
>> + if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC) {
>> + ret = print_graph_proc(s, ent->pid);
>> + if (ret == TRACE_TYPE_PARTIAL_LINE)
>> + return TRACE_TYPE_PARTIAL_LINE;
>> +
>> + ret = trace_seq_printf(s, " | ");
>> + if (!ret)
>> + return TRACE_TYPE_PARTIAL_LINE;
>> + }
>> +
>> + /* No overhead */
>> + if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
>> + ret = trace_seq_printf(s, " ");
>> + if (!ret)
>> + return TRACE_TYPE_PARTIAL_LINE;
>> + }
>> +
>> + /* No time */
>> + ret = trace_seq_printf(s, " | ");
>> + if (!ret)
>> + return TRACE_TYPE_PARTIAL_LINE;
>> +
>> + /* Indentation */
>> + if (trace->depth > 0)
>> + for (i = 0; i < (trace->depth + 1) * TRACE_GRAPH_INDENT; i++) {
>> + ret = trace_seq_printf(s, " ");
>> + if (!ret)
>> + return TRACE_TYPE_PARTIAL_LINE;
>> + }
>> +
>> + /* The comment */
>> + ret = trace_seq_printf(s, "/* %s", trace->buf);
>> + if (!ret)
>> + return TRACE_TYPE_PARTIAL_LINE;
>> +
>> + if (ent->flags & TRACE_FLAG_CONT)
>> + trace_seq_print_cont(s, iter);
>> +
>> + ret = trace_seq_printf(s, " */\n");
>> + if (!ret)
>> + return TRACE_TYPE_PARTIAL_LINE;
>> +
>> + return TRACE_TYPE_HANDLED;
>> +}
>> +
>> +
>> enum print_line_t
>> print_graph_function(struct trace_iterator *iter)
>> {
>> @@ -495,6 +560,11 @@ print_graph_function(struct trace_iterator *iter)
>> trace_assign_type(field, entry);
>> return print_graph_return(&field->ret, s, entry, iter->cpu);
>> }
>> + case TRACE_PRINT: {
>> + struct print_entry *field;
>> + trace_assign_type(field, entry);
>> + return print_graph_comment(field, s, entry, iter);
>> + }
>> default:
>> return TRACE_TYPE_UNHANDLED;
>> }
>> diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
>> index 2a98a20..2fb6da6 100644
>> --- a/kernel/trace/trace_mmiotrace.c
>> +++ b/kernel/trace/trace_mmiotrace.c
>> @@ -366,5 +366,5 @@ void mmio_trace_mapping(struct mmiotrace_map *map)
>>
>> int mmio_trace_printk(const char *fmt, va_list args)
>> {
>> - return trace_vprintk(0, fmt, args);
>> + return trace_vprintk(0, -1, fmt, args);
>> }
>> --
>
>
> Other than what I commented above.
>
> Acked-by: Steven Rostedt <srostedt@...hat.com>
Thanks!
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