lkml.org 
[lkml]   [2022]   [Oct]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.15 114/530] tracing: Add ioctl() to force ring buffer waiters to wake up
    Date
    From: Steven Rostedt (Google) <rostedt@goodmis.org>

    commit 01b2a52171735c6eea80ee2f355f32bea6c41418 upstream.

    If a process is waiting on the ring buffer for data, there currently isn't
    a clean way to force it to wake up. Add an ioctl call that will force any
    tasks that are waiting on the trace_pipe_raw file to wake up.

    Link: https://lkml.kernel.org/r/20220929095029.117f913f@gandalf.local.home

    Cc: stable@vger.kernel.org
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Fixes: e30f53aad2202 ("tracing: Do not busy wait in buffer splice")
    Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    kernel/trace/trace.c | 22 ++++++++++++++++++++++
    1 file changed, 22 insertions(+)

    --- a/kernel/trace/trace.c
    +++ b/kernel/trace/trace.c
    @@ -8310,12 +8310,34 @@ out:
    return ret;
    }

    +/* An ioctl call with cmd 0 to the ring buffer file will wake up all waiters */
    +static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
    +{
    + struct ftrace_buffer_info *info = file->private_data;
    + struct trace_iterator *iter = &info->iter;
    +
    + if (cmd)
    + return -ENOIOCTLCMD;
    +
    + mutex_lock(&trace_types_lock);
    +
    + iter->wait_index++;
    + /* Make sure the waiters see the new wait_index */
    + smp_wmb();
    +
    + ring_buffer_wake_waiters(iter->array_buffer->buffer, iter->cpu_file);
    +
    + mutex_unlock(&trace_types_lock);
    + return 0;
    +}
    +
    static const struct file_operations tracing_buffers_fops = {
    .open = tracing_buffers_open,
    .read = tracing_buffers_read,
    .poll = tracing_buffers_poll,
    .release = tracing_buffers_release,
    .splice_read = tracing_buffers_splice_read,
    + .unlocked_ioctl = tracing_buffers_ioctl,
    .llseek = no_llseek,
    };


    \
     
     \ /
      Last update: 2022-10-25 01:31    [W:4.083 / U:0.436 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site