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tracing: Add ioctl() to force ring buffer waiters to wake up

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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: e30f53aad2 ("tracing: Do not busy wait in buffer splice")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2022-09-29 09:50:29 -04:00
parent f3ddb74ad0
commit 01b2a52171
1 changed files with 22 additions and 0 deletions
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22
kernel/trace/trace.c
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@ -8349,12 +8349,34 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
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,
};