From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Vasily Averin <vvs@virtuozzo.com>
Subject: [for-next][PATCH 04/21] ftrace: fpid_next() should increase position index
Date: Thu, 30 Jan 2020 09:47:47 -0500 [thread overview]
Message-ID: <20200130144810.820818412@goodmis.org> (raw)
In-Reply-To: 20200130144743.527378179@goodmis.org
From: Vasily Averin <vvs@virtuozzo.com>
if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.
Without patch:
# dd bs=4 skip=1 if=/sys/kernel/tracing/set_ftrace_pid
dd: /sys/kernel/tracing/set_ftrace_pid: cannot skip to specified offset
id
no pid
2+1 records in
2+1 records out
10 bytes copied, 0.000213285 s, 46.9 kB/s
Notice the "id" followed by "no pid".
With the patch:
# dd bs=4 skip=1 if=/sys/kernel/tracing/set_ftrace_pid
dd: /sys/kernel/tracing/set_ftrace_pid: cannot skip to specified offset
id
0+1 records in
0+1 records out
3 bytes copied, 0.000202112 s, 14.8 kB/s
Notice that it only prints "id" and not the "no pid" afterward.
Link: http://lkml.kernel.org/r/4f87c6ad-f114-30bb-8506-c32274ce2992@virtuozzo.com
https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/ftrace.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index fdb1a9532420..0e9612c30995 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -7026,9 +7026,10 @@ static void *fpid_next(struct seq_file *m, void *v, loff_t *pos)
struct trace_array *tr = m->private;
struct trace_pid_list *pid_list = rcu_dereference_sched(tr->function_pids);
- if (v == FTRACE_NO_PIDS)
+ if (v == FTRACE_NO_PIDS) {
+ (*pos)++;
return NULL;
-
+ }
return trace_pid_next(pid_list, v, pos);
}
--
2.24.1
next prev parent reply other threads:[~2020-01-30 14:49 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-30 14:47 [for-next][PATCH 00/21] tracing: Some more last minute updates for 5.6 Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 01/21] tracing/boot: Include required headers and sort it alphabetically Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 02/21] tracing/boot: Move external function declarations to kernel/trace/trace.h Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 03/21] tracing: Fix sched switch start/stop refcount racy updates Steven Rostedt
2020-01-30 14:47 ` Steven Rostedt [this message]
2020-01-30 14:47 ` [for-next][PATCH 05/21] tracing: eval_map_next() should always increase position index Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 06/21] trigger_next should " Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 07/21] tracing: Add trace_array_find/_get() to find instance trace arrays Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 08/21] tracing: Add trace_get/put_event_file() Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 09/21] tracing: Add synth_event_delete() Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 10/21] tracing: Add dynamic event command creation interface Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 11/21] tracing: Add synthetic event command generation functions Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 12/21] tracing: Add synth_event_trace() and related functions Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 13/21] tracing: Add synth event generation test module Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 14/21] tracing: Add kprobe event command generation functions Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 15/21] tracing: Change trace_boot to use kprobe_event interface Steven Rostedt
2020-01-30 14:47 ` [for-next][PATCH 16/21] tracing: Add kprobe event command generation test module Steven Rostedt
2020-01-30 14:48 ` [for-next][PATCH 17/21] tracing: Documentation for in-kernel synthetic event API Steven Rostedt
2020-01-30 14:48 ` [for-next][PATCH 18/21] tracing: Move all function tracing configs together Steven Rostedt
2020-01-30 14:48 ` [for-next][PATCH 19/21] tracing: Move tracing test module " Steven Rostedt
2020-01-30 14:48 ` [for-next][PATCH 20/21] tracing: Move mmio tracer config up with the other tracers Steven Rostedt
2020-01-30 14:48 ` [for-next][PATCH 21/21] tracing: Move tracing selftests to bottom of menu Steven Rostedt
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