* [PATCH] tracing: Fix the unusable problem caused by non-empty pipe_cpumask
@ 2023-09-01 7:26 Chuang Wang
2023-09-01 14:02 ` Masami Hiramatsu
0 siblings, 1 reply; 3+ messages in thread
From: Chuang Wang @ 2023-09-01 7:26 UTC (permalink / raw)
Cc: Chuang Wang, stable, Steven Rostedt, Masami Hiramatsu,
Zheng Yejian, linux-kernel, linux-trace-kernel
There is a problem in the linux-6.5 when I execute the following
command:
$ perf ftrace -t irqsoff
failed to open trace_pipe
At the same time, when I open this file, the same error occurs.
Therefore, after carefully looking at the code, the open function of
'trace_pipe' returns -EBUSY in open_pipe_on_cpu() because no clearing
operation was performed when 'trace_array->pipe_cpumask' was allocated.
With this patch, Use zalloc_cpumask_var() to ensure that
'trace_array->pipe_cpumask' is reset to 0 when allocated.
Cc: stable@vger.kernel.org
Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
---
kernel/trace/trace.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d8233d34b5a0..c0b8a72f3466 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9461,7 +9461,7 @@ static struct trace_array *trace_array_create(const char *name)
if (!alloc_cpumask_var(&tr->tracing_cpumask, GFP_KERNEL))
goto out_free_tr;
- if (!alloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL))
+ if (!zalloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL))
goto out_free_tr;
tr->trace_flags = global_trace.trace_flags & ~ZEROED_TRACE_FLAGS;
@@ -10406,7 +10406,7 @@ __init static int tracer_alloc_buffers(void)
if (trace_create_savedcmd() < 0)
goto out_free_temp_buffer;
- if (!alloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL))
+ if (!zalloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL))
goto out_free_savedcmd;
/* TODO: make the number of buffers hot pluggable with CPUS */
--
2.39.2
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] tracing: Fix the unusable problem caused by non-empty pipe_cpumask
2023-09-01 7:26 [PATCH] tracing: Fix the unusable problem caused by non-empty pipe_cpumask Chuang Wang
@ 2023-09-01 14:02 ` Masami Hiramatsu
2023-09-02 1:26 ` Steven Rostedt
0 siblings, 1 reply; 3+ messages in thread
From: Masami Hiramatsu @ 2023-09-01 14:02 UTC (permalink / raw)
To: Chuang Wang
Cc: stable, Steven Rostedt, Masami Hiramatsu, Zheng Yejian,
linux-kernel, linux-trace-kernel
On Fri, 1 Sep 2023 15:26:26 +0800
Chuang Wang <nashuiliang@gmail.com> wrote:
> There is a problem in the linux-6.5 when I execute the following
> command:
>
> $ perf ftrace -t irqsoff
> failed to open trace_pipe
>
> At the same time, when I open this file, the same error occurs.
>
> Therefore, after carefully looking at the code, the open function of
> 'trace_pipe' returns -EBUSY in open_pipe_on_cpu() because no clearing
> operation was performed when 'trace_array->pipe_cpumask' was allocated.
>
> With this patch, Use zalloc_cpumask_var() to ensure that
> 'trace_array->pipe_cpumask' is reset to 0 when allocated.
Good catch. This looks good to me.
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Cc: stable@vger.kernel.org
> Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
> Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
> ---
> kernel/trace/trace.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index d8233d34b5a0..c0b8a72f3466 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -9461,7 +9461,7 @@ static struct trace_array *trace_array_create(const char *name)
> if (!alloc_cpumask_var(&tr->tracing_cpumask, GFP_KERNEL))
> goto out_free_tr;
>
> - if (!alloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL))
> + if (!zalloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL))
> goto out_free_tr;
>
> tr->trace_flags = global_trace.trace_flags & ~ZEROED_TRACE_FLAGS;
> @@ -10406,7 +10406,7 @@ __init static int tracer_alloc_buffers(void)
> if (trace_create_savedcmd() < 0)
> goto out_free_temp_buffer;
>
> - if (!alloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL))
> + if (!zalloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL))
> goto out_free_savedcmd;
>
> /* TODO: make the number of buffers hot pluggable with CPUS */
> --
> 2.39.2
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] tracing: Fix the unusable problem caused by non-empty pipe_cpumask
2023-09-01 14:02 ` Masami Hiramatsu
@ 2023-09-02 1:26 ` Steven Rostedt
0 siblings, 0 replies; 3+ messages in thread
From: Steven Rostedt @ 2023-09-02 1:26 UTC (permalink / raw)
To: Masami Hiramatsu (Google)
Cc: Chuang Wang, stable, Zheng Yejian, linux-kernel,
linux-trace-kernel, Brian Foster
On Fri, 1 Sep 2023 23:02:06 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> On Fri, 1 Sep 2023 15:26:26 +0800
> Chuang Wang <nashuiliang@gmail.com> wrote:
>
> > There is a problem in the linux-6.5 when I execute the following
> > command:
> >
> > $ perf ftrace -t irqsoff
> > failed to open trace_pipe
> >
> > At the same time, when I open this file, the same error occurs.
> >
> > Therefore, after carefully looking at the code, the open function of
> > 'trace_pipe' returns -EBUSY in open_pipe_on_cpu() because no clearing
> > operation was performed when 'trace_array->pipe_cpumask' was allocated.
> >
> > With this patch, Use zalloc_cpumask_var() to ensure that
> > 'trace_array->pipe_cpumask' is reset to 0 when allocated.
Brian Foster beat you to it.
https://lore.kernel.org/linux-trace-kernel/20230831125500.986862-1-bfoster@redhat.com
>
> Good catch. This looks good to me.
>
> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
Masami, I'll add your Reviewed-by to that commit.
Thanks!
-- Steve
> >
> > Cc: stable@vger.kernel.org
> > Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
> > Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
> > ---
> > kernel/trace/trace.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index d8233d34b5a0..c0b8a72f3466 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -9461,7 +9461,7 @@ static struct trace_array *trace_array_create(const char *name)
> > if (!alloc_cpumask_var(&tr->tracing_cpumask, GFP_KERNEL))
> > goto out_free_tr;
> >
> > - if (!alloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL))
> > + if (!zalloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL))
> > goto out_free_tr;
> >
> > tr->trace_flags = global_trace.trace_flags & ~ZEROED_TRACE_FLAGS;
> > @@ -10406,7 +10406,7 @@ __init static int tracer_alloc_buffers(void)
> > if (trace_create_savedcmd() < 0)
> > goto out_free_temp_buffer;
> >
> > - if (!alloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL))
> > + if (!zalloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL))
> > goto out_free_savedcmd;
> >
> > /* TODO: make the number of buffers hot pluggable with CPUS */
> > --
> > 2.39.2
> >
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-09-01 7:26 [PATCH] tracing: Fix the unusable problem caused by non-empty pipe_cpumask Chuang Wang
2023-09-01 14:02 ` Masami Hiramatsu
2023-09-02 1:26 ` Steven Rostedt
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