Messages in this thread | | | Date | Thu, 19 Mar 2009 21:26:32 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 1/7] tracing: give easy way to clear trace buffer |
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On Thu, Mar 19, 2009 at 04:01:23PM -0400, Steven Rostedt wrote: > From: Steven Rostedt <srostedt@redhat.com> > > There is currently no easy way to clear the trace buffer. Currently > the only way is to change the current tracer. > > This patch lets the user clear the trace buffer by simply writing > into the trace files. > > echo > /debug/tracing/trace > > or to clear a single cpu (i.e. for CPU 1): > > echo > /debug/tracing/per_cpu/cpu1/trace > > Requested-by: Ingo Molnar <mingo@elte.hu> > Signed-off-by: Steven Rostedt <srostedt@redhat.com> > --- > kernel/trace/trace.c | 41 +++++++++++++++++++++++++++++++++-------- > 1 files changed, 33 insertions(+), 8 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index a2d13e8..8d981ab 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -1941,9 +1941,14 @@ int tracing_open_generic(struct inode *inode, struct file *filp) > static int tracing_release(struct inode *inode, struct file *file) > { > struct seq_file *m = (struct seq_file *)file->private_data; > - struct trace_iterator *iter = m->private; > + struct trace_iterator *iter; > int cpu; > > + if (!(file->f_mode & FMODE_READ)) > + return 0; > + > + iter = m->private; > + > mutex_lock(&trace_types_lock); > for_each_tracing_cpu(cpu) { > if (iter->buffer_iter[cpu]) > @@ -1969,12 +1974,24 @@ static int tracing_open(struct inode *inode, struct file *file) > struct trace_iterator *iter; > int ret = 0; > > - iter = __tracing_open(inode, file); > - if (IS_ERR(iter)) > - ret = PTR_ERR(iter); > - else if (trace_flags & TRACE_ITER_LATENCY_FMT) > - iter->iter_flags |= TRACE_FILE_LAT_FMT; > + /* If this file was open for write, then erase contents */ > + if ((file->f_mode & FMODE_WRITE) && > + !(file->f_flags & O_APPEND)) { > + long cpu = (long) inode->i_private; > + > + if (cpu == TRACE_PIPE_ALL_CPU) > + tracing_reset_online_cpus(&global_trace); > + else > + tracing_reset(&global_trace, cpu); > + } > > + if (file->f_mode & FMODE_READ) { > + iter = __tracing_open(inode, file); > + if (IS_ERR(iter)) > + ret = PTR_ERR(iter); > + else if (trace_flags & TRACE_ITER_LATENCY_FMT) > + iter->iter_flags |= TRACE_FILE_LAT_FMT; > + } > return ret; > } > > @@ -2049,9 +2066,17 @@ static int show_traces_open(struct inode *inode, struct file *file) > return ret; > } > > +static ssize_t > +tracing_write_stub(struct file *filp, const char __user *ubuf, > + size_t count, loff_t *ppos) > +{ > + return count; > +}
Is this one necessary? I guess debugfs or vfs layers already provide a stub for write. No?
Anyway, that's a small detail for this good patch idea.
Frederic.
> static const struct file_operations tracing_fops = { > .open = tracing_open, > .read = seq_read, > + .write = tracing_write_stub, > .llseek = seq_lseek, > .release = tracing_release, > }; > @@ -3576,7 +3601,7 @@ static void tracing_init_debugfs_percpu(long cpu) > pr_warning("Could not create debugfs 'trace_pipe' entry\n"); > > /* per cpu trace */ > - entry = debugfs_create_file("trace", 0444, d_cpu, > + entry = debugfs_create_file("trace", 0644, d_cpu, > (void *) cpu, &tracing_fops); > if (!entry) > pr_warning("Could not create debugfs 'trace' entry\n"); > @@ -3890,7 +3915,7 @@ static __init int tracer_init_debugfs(void) > if (!entry) > pr_warning("Could not create debugfs 'tracing_cpumask' entry\n"); > > - entry = debugfs_create_file("trace", 0444, d_tracer, > + entry = debugfs_create_file("trace", 0644, d_tracer, > (void *) TRACE_PIPE_ALL_CPU, &tracing_fops); > if (!entry) > pr_warning("Could not create debugfs 'trace' entry\n"); > -- > 1.6.2 > > -- > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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