2012-11-13 01:53:14

by Shan Wei

Subject: [PATCH v4 7/9] trace: use this_cpu_ptr per-cpu helper

From: Shan Wei <[email protected]>

typeof(&buffer) is a pointer to array of 1024 char, or char (*)[1024].
But, typeof(&buffer[0]) is a pointer to char which match the return type of get_trace_buf().
As well-known, the value of &buffer is equal to &buffer[0].
so return this_cpu_ptr(&percpu_buffer->buffer[0]) can avoid type cast.

Signed-off-by: Shan Wei <[email protected]>
---
v4: avoid type cast using &percpu_buffer->buffer[0].
---
kernel/trace/blktrace.c | 2 +-
kernel/trace/trace.c | 5 +----
2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index c0bd030..71259e2 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -147,7 +147,7 @@ void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
return;

local_irq_save(flags);
- buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
+ buf = this_cpu_ptr(bt->msg_data);
va_start(args, fmt);
n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);
va_end(args);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 31e4f55..65cb003 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1495,7 +1495,6 @@ static struct trace_buffer_struct *trace_percpu_nmi_buffer;
static char *get_trace_buf(void)
{
struct trace_buffer_struct *percpu_buffer;
- struct trace_buffer_struct *buffer;

/*
* If we have allocated per cpu buffers, then we do not
@@ -1513,9 +1512,7 @@ static char *get_trace_buf(void)
if (!percpu_buffer)
return NULL;

- buffer = per_cpu_ptr(percpu_buffer, smp_processor_id());
-
- return buffer->buffer;
+ return this_cpu_ptr(&percpu_buffer->buffer[0]);
}

static int alloc_percpu_trace_buffer(void)
--
1.7.1

2012-11-16 08:34:24

by Shan Wei

Subject: Re: [PATCH v4 7/9] trace: use this_cpu_ptr per-cpu helper

Shan Wei said, at 2012/11/13 9:53:
> From: Shan Wei <[email protected]>
>
> typeof(&buffer) is a pointer to array of 1024 char, or char (*)[1024].
> But, typeof(&buffer[0]) is a pointer to char which match the return type of get_trace_buf().
> As well-known, the value of &buffer is equal to &buffer[0].
> so return this_cpu_ptr(&percpu_buffer->buffer[0]) can avoid type cast.
>
> Signed-off-by: Shan Wei <[email protected]>

Steven Rostedt, would you like to pick it up to your tree?

> ---
> v4: avoid type cast using &percpu_buffer->buffer[0].
> ---
> kernel/trace/blktrace.c | 2 +-
> kernel/trace/trace.c | 5 +----
> 2 files changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index c0bd030..71259e2 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -147,7 +147,7 @@ void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
> return;
>
> local_irq_save(flags);
> - buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
> + buf = this_cpu_ptr(bt->msg_data);
> va_start(args, fmt);
> n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);
> va_end(args);
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 31e4f55..65cb003 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -1495,7 +1495,6 @@ static struct trace_buffer_struct *trace_percpu_nmi_buffer;
> static char *get_trace_buf(void)
> {
> struct trace_buffer_struct *percpu_buffer;
> - struct trace_buffer_struct *buffer;
>
> /*
> * If we have allocated per cpu buffers, then we do not
> @@ -1513,9 +1512,7 @@ static char *get_trace_buf(void)
> if (!percpu_buffer)
> return NULL;
>
> - buffer = per_cpu_ptr(percpu_buffer, smp_processor_id());
> -
> - return buffer->buffer;
> + return this_cpu_ptr(&percpu_buffer->buffer[0]);
> }
>
> static int alloc_percpu_trace_buffer(void)
>

2012-11-30 06:38:27

by Shan Wei

Subject: Re: [PATCH v4 7/9] trace: use this_cpu_ptr per-cpu helper

Shan Wei said, at 2012/11/16 16:34:
> Shan Wei said, at 2012/11/13 9:53:
>> From: Shan Wei <[email protected]>
>>
>> typeof(&buffer) is a pointer to array of 1024 char, or char (*)[1024].
>> But, typeof(&buffer[0]) is a pointer to char which match the return type of get_trace_buf().
>> As well-known, the value of &buffer is equal to &buffer[0].
>> so return this_cpu_ptr(&percpu_buffer->buffer[0]) can avoid type cast.
>>
>> Signed-off-by: Shan Wei <[email protected]>
>
> Steven Rostedt, would you like to pick it up to your tree?

ping......................