diff options
| author | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2025-05-22 18:54:52 +0300 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2025-05-29 15:24:07 +0300 |
| commit | 32dc0042528d385d83bf458e4cf3a49c5110afea (patch) | |
| tree | 926be55a34749a547827f299edd26f06852ce1a3 | |
| parent | c2a08311427cc8c5c547e5d700cb2f93d63fcb2a (diff) | |
| download | linux-32dc0042528d385d83bf458e4cf3a49c5110afea.tar.xz | |
tracing: Reset last-boot buffers when reading out all cpu buffers
Reset the last-boot ring buffers when read() reads out all cpu
buffers through trace_pipe/trace_pipe_raw. This prevents ftrace to
unwind ring buffer read pointer next boot.
Note that this resets only when all per-cpu buffers are empty, and
read via read(2) syscall. For example, if you read only one of the
per-cpu trace_pipe, it does not reset it. Also, reading buffer by
splice(2) syscall does not reset because some data in the reader
(the last) page.
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/174792929202.496143.8184644221859580999.stgit@mhiramat.tok.corp.google.com
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/trace.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 73d75cdb7e5b..ecb774cc01ab 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6610,6 +6610,22 @@ static int tracing_wait_pipe(struct file *filp) return 1; } +static bool update_last_data_if_empty(struct trace_array *tr) +{ + if (!(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) + return false; + + if (!ring_buffer_empty(tr->array_buffer.buffer)) + return false; + + /* + * If the buffer contains the last boot data and all per-cpu + * buffers are empty, reset it from the kernel side. + */ + update_last_data(tr); + return true; +} + /* * Consumer reader. */ @@ -6641,6 +6657,9 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, } waitagain: + if (update_last_data_if_empty(iter->tr)) + return 0; + sret = tracing_wait_pipe(filp); if (sret <= 0) return sret; @@ -8167,6 +8186,9 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, if (ret < 0) { if (trace_empty(iter) && !iter->closed) { + if (update_last_data_if_empty(iter->tr)) + return 0; + if ((filp->f_flags & O_NONBLOCK)) return -EAGAIN; |