[PATCH] tracing: fix trace_print_seq()

[PATCH] tracing: fix trace_print_seq()

[Xiao Guangrong]

We will lose something if trace_seq->buffer[0] is 0, because the copy length
is calculated by strlen() in seq_puts(), so using seq_write() instead of 
seq_puts().

There have a example:
after reboot:
# echo kmemtrace > current_tracer
# echo 0 > options/kmem_minimalistic
# cat trace
# tracer: kmemtrace
#
#
Nothing is exported, because the first byte of trace_seq->buffer[ ]
is KMEMTRACE_USER_ALLOC.
( the value of KMEMTRACE_USER_ALLOC is zero, seeing
  kmemtrace_print_alloc_user() in kernel/trace/kmemtrace.c)

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 kernel/trace/trace_output.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 7938f3a..e0c2545 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -27,8 +27,7 @@ void trace_print_seq(struct seq_file *m, struct trace_seq *s)
 {
 	int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
 
-	s->buffer[len] = 0;
-	seq_puts(m, s->buffer);
+	seq_write(m, s->buffer, len);
 
 	trace_seq_init(s);
 }
-- 
1.6.1.2

Re: [PATCH] tracing: fix trace_print_seq()

[Frederic Weisbecker]

On Wed, Jul 01, 2009 at 04:50:25PM +0800, Xiao Guangrong wrote:
> We will lose something if trace_seq->buffer[0] is 0, because the copy length
> is calculated by strlen() in seq_puts(), so using seq_write() instead of 
> seq_puts().
> 
> There have a example:
> after reboot:
> # echo kmemtrace > current_tracer
> # echo 0 > options/kmem_minimalistic
> # cat trace
> # tracer: kmemtrace
> #
> #
> Nothing is exported, because the first byte of trace_seq->buffer[ ]
> is KMEMTRACE_USER_ALLOC.
> ( the value of KMEMTRACE_USER_ALLOC is zero, seeing
>   kmemtrace_print_alloc_user() in kernel/trace/kmemtrace.c)
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> ---
>  kernel/trace/trace_output.c |    3 +--
>  1 files changed, 1 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> index 7938f3a..e0c2545 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -27,8 +27,7 @@ void trace_print_seq(struct seq_file *m, struct trace_seq *s)
>  {
>  	int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
>  
> -	s->buffer[len] = 0;
> -	seq_puts(m, s->buffer);
> +	seq_write(m, s->buffer, len);
>  
>  	trace_seq_init(s);
>  }
> -- 
> 1.6.1.2
> 

Looks good, thanks.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>

But having a '\0' in a non binary trace looks weird. Why do
we have such plain KMEMTRACE_USER_ALLOC whereas binary tracing
is not set, as your example shows it?

[tip:tracing/urgent] tracing: Fix trace_print_seq()

[tip-bot for Xiao Guangrong]

Commit-ID:  5c37f525657e879a17a27c83021602cd55837531
Gitweb:     http://git.kernel.org/tip/5c37f525657e879a17a27c83021602cd55837531
Author:     Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
AuthorDate: Wed, 1 Jul 2009 16:50:25 +0800
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 1 Jul 2009 16:03:50 +0200

tracing: Fix trace_print_seq()

We will lose something if trace_seq->buffer[0] is 0, because the copy length
is calculated by strlen() in seq_puts(), so using seq_write() instead of
seq_puts().

There have a example:
after reboot:

 # echo kmemtrace > current_tracer
 # echo 0 > options/kmem_minimalistic
 # cat trace
 # tracer: kmemtrace
 #
 #

Nothing is exported, because the first byte of trace_seq->buffer[ ]
is KMEMTRACE_USER_ALLOC.

( the value of KMEMTRACE_USER_ALLOC is zero, seeing
  kmemtrace_print_alloc_user() in kernel/trace/kmemtrace.c)

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
LKML-Reference: <4A4B2351.5010300@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 kernel/trace/trace_output.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 7938f3a..e0c2545 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -27,8 +27,7 @@ void trace_print_seq(struct seq_file *m, struct trace_seq *s)
 {
 	int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
 
-	s->buffer[len] = 0;
-	seq_puts(m, s->buffer);
+	seq_write(m, s->buffer, len);
 
 	trace_seq_init(s);
 }

Re: [tip:tracing/urgent] tracing: Fix trace_print_seq()

[Pekka Enberg]

On Wed, 2009-07-01 at 14:06 +0000, tip-bot for Xiao Guangrong wrote:
> Commit-ID:  5c37f525657e879a17a27c83021602cd55837531
> Gitweb:     http://git.kernel.org/tip/5c37f525657e879a17a27c83021602cd55837531
> Author:     Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> AuthorDate: Wed, 1 Jul 2009 16:50:25 +0800
> Committer:  Ingo Molnar <mingo@elte.hu>
> CommitDate: Wed, 1 Jul 2009 16:03:50 +0200
> 
> tracing: Fix trace_print_seq()
> 
> We will lose something if trace_seq->buffer[0] is 0, because the copy length
> is calculated by strlen() in seq_puts(), so using seq_write() instead of
> seq_puts().
> 
> There have a example:
> after reboot:
> 
>  # echo kmemtrace > current_tracer
>  # echo 0 > options/kmem_minimalistic
>  # cat trace
>  # tracer: kmemtrace
>  #
>  #
> 
> Nothing is exported, because the first byte of trace_seq->buffer[ ]
> is KMEMTRACE_USER_ALLOC.
> 
> ( the value of KMEMTRACE_USER_ALLOC is zero, seeing
>   kmemtrace_print_alloc_user() in kernel/trace/kmemtrace.c)
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Pekka Enberg <penberg@cs.helsinki.fi>
> LKML-Reference: <4A4B2351.5010300@cn.fujitsu.com>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>

Nice catch!

Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>

[tip:tracing/urgent] tracing: Fix trace_print_seq()

[tip-bot for Xiao Guangrong]

Commit-ID:  393ab9a2a6cf958c9549e35bd88c03b9b3eae64e
Gitweb:     http://git.kernel.org/tip/393ab9a2a6cf958c9549e35bd88c03b9b3eae64e
Author:     Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
AuthorDate: Wed, 1 Jul 2009 16:50:25 +0800
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 1 Jul 2009 16:41:31 +0200

tracing: Fix trace_print_seq()

We will lose something if trace_seq->buffer[0] is 0, because the copy length
is calculated by strlen() in seq_puts(), so using seq_write() instead of
seq_puts().

There have a example:
after reboot:

 # echo kmemtrace > current_tracer
 # echo 0 > options/kmem_minimalistic
 # cat trace
 # tracer: kmemtrace
 #
 #

Nothing is exported, because the first byte of trace_seq->buffer[ ]
is KMEMTRACE_USER_ALLOC.

( the value of KMEMTRACE_USER_ALLOC is zero, seeing
  kmemtrace_print_alloc_user() in kernel/trace/kmemtrace.c)

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A4B2351.5010300@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 kernel/trace/trace_output.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 7938f3a..e0c2545 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -27,8 +27,7 @@ void trace_print_seq(struct seq_file *m, struct trace_seq *s)
 {
 	int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
 
-	s->buffer[len] = 0;
-	seq_puts(m, s->buffer);
+	seq_write(m, s->buffer, len);
 
 	trace_seq_init(s);
 }

Re: [PATCH] tracing: fix trace_print_seq()

[Li Zefan]

>> There have a example:
>> after reboot:
>> # echo kmemtrace > current_tracer
>> # echo 0 > options/kmem_minimalistic
>> # cat trace
>> # tracer: kmemtrace
>> #
>> #
>> Nothing is exported, because the first byte of trace_seq->buffer[ ]
>> is KMEMTRACE_USER_ALLOC.
>> ( the value of KMEMTRACE_USER_ALLOC is zero, seeing
>>   kmemtrace_print_alloc_user() in kernel/trace/kmemtrace.c)
>>
...
> Looks good, thanks.
> 
> Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
> 
> But having a '\0' in a non binary trace looks weird. Why do
> we have such plain KMEMTRACE_USER_ALLOC whereas binary tracing
> is not set, as your example shows it?
> 

Because of this commit:

| commit 42af9054c0eeed09ec58d13ec8bf52d225ebcfcc
| Author: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
| Date:   Mon Mar 23 15:12:26 2009 +0200
|
|    kmemtrace: restore original tracing data binary format, improve ABI

I think we should change it to use trace_event->binary() interface for
binary trace.

[tip:tracing/urgent] tracing: Fix trace_print_seq()

[tip-bot for Xiao Guangrong]

Commit-ID:  e1af3aec3e2e7d21d4b3054323779d478c19d907
Gitweb:     http://git.kernel.org/tip/e1af3aec3e2e7d21d4b3054323779d478c19d907
Author:     Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
AuthorDate: Wed, 1 Jul 2009 16:50:25 +0800
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 2 Jul 2009 08:51:13 +0200

tracing: Fix trace_print_seq()

We will lose something if trace_seq->buffer[0] is 0, because the copy length
is calculated by strlen() in seq_puts(), so using seq_write() instead of
seq_puts().

There have a example:
after reboot:

 # echo kmemtrace > current_tracer
 # echo 0 > options/kmem_minimalistic
 # cat trace
 # tracer: kmemtrace
 #
 #

Nothing is exported, because the first byte of trace_seq->buffer[ ]
is KMEMTRACE_USER_ALLOC.

( the value of KMEMTRACE_USER_ALLOC is zero, seeing
  kmemtrace_print_alloc_user() in kernel/trace/kmemtrace.c)

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A4B2351.5010300@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 kernel/trace/trace_output.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 7938f3a..e0c2545 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -27,8 +27,7 @@ void trace_print_seq(struct seq_file *m, struct trace_seq *s)
 {
 	int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
 
-	s->buffer[len] = 0;
-	seq_puts(m, s->buffer);
+	seq_write(m, s->buffer, len);
 
 	trace_seq_init(s);
 }