* [PATCH] kernel/module: Use BUG_ON instead of if condition followed by BUG.
@ 2021-03-30 12:07 zhouchuangao
2021-04-12 13:04 ` Jessica Yu
0 siblings, 1 reply; 4+ messages in thread
From: zhouchuangao @ 2021-03-30 12:07 UTC (permalink / raw)
To: Jessica Yu, linux-kernel; +Cc: zhouchuangao
It can be optimized at compile time.
Signed-off-by: zhouchuangao <zhouchuangao@vivo.com>
---
kernel/module.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c
index 3047935..f46fc4f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1014,8 +1014,8 @@ void __symbol_put(const char *symbol)
};
preempt_disable();
- if (!find_symbol(&fsa))
- BUG();
+ BUG_ON(!find_symbol(&fsa));
+
module_put(fsa.owner);
preempt_enable();
}
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] kernel/module: Use BUG_ON instead of if condition followed by BUG.
2021-03-30 12:07 [PATCH] kernel/module: Use BUG_ON instead of if condition followed by BUG zhouchuangao
@ 2021-04-12 13:04 ` Jessica Yu
2021-04-13 7:21 ` 周传高
0 siblings, 1 reply; 4+ messages in thread
From: Jessica Yu @ 2021-04-12 13:04 UTC (permalink / raw)
To: zhouchuangao; +Cc: linux-kernel
+++ zhouchuangao [30/03/21 05:07 -0700]:
>It can be optimized at compile time.
>
>Signed-off-by: zhouchuangao <zhouchuangao@vivo.com>
Hi,
Could you please provide a more descriptive changelog? I.e., Is this
a fix for a cocinelle warning? What are the optimization(s)?
Thanks,
Jessica
>---
> kernel/module.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index 3047935..f46fc4f 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -1014,8 +1014,8 @@ void __symbol_put(const char *symbol)
> };
>
> preempt_disable();
>- if (!find_symbol(&fsa))
>- BUG();
>+ BUG_ON(!find_symbol(&fsa));
>+
> module_put(fsa.owner);
> preempt_enable();
> }
>--
>2.7.4
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re:Re: [PATCH] kernel/module: Use BUG_ON instead of if condition followed by BUG.
2021-04-12 13:04 ` Jessica Yu
@ 2021-04-13 7:21 ` 周传高
2021-04-13 12:42 ` Jessica Yu
0 siblings, 1 reply; 4+ messages in thread
From: 周传高 @ 2021-04-13 7:21 UTC (permalink / raw)
To: Jessica Yu; +Cc: linux-kernel
>+++ zhouchuangao [30/03/21 05:07 -0700]:
>>It can be optimized at compile time.
>>
>>Signed-off-by: zhouchuangao <zhouchuangao@vivo.com>
>
>Hi,
>
>Could you please provide a more descriptive changelog? I.e., Is this
>a fix for a cocinelle warning? What are the optimization(s)?
>
>Thanks,
>
First,
This patch comes from cocinelle warning.
Second,
#define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
BUG_ON uses unlikely in if(). Through disassembly, we can see that
brk #0x800 is compiled to the end of the function.
As you can see below:
......
ffffff8008660bec: d65f03c0 ret
ffffff8008660bf0: d4210000 brk #0x800
Usually, the condition in if () is not satisfied. For the multi-stage pipeline,
we do not need to perform fetch decode and excute operation on brk
instruction.
In my opinion, this can improve the efficiency of the multi-stage pipeline.
Thanks,
zhouchuangao
>Jessica
>
>>---
>> kernel/module.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>>diff --git a/kernel/module.c b/kernel/module.c
>>index 3047935..f46fc4f 100644
>>--- a/kernel/module.c
>>+++ b/kernel/module.c
>>@@ -1014,8 +1014,8 @@ void __symbol_put(const char *symbol)
>> };
>>
>> preempt_disable();
>>- if (!find_symbol(&fsa))
>>- BUG();
>>+ BUG_ON(!find_symbol(&fsa));
>>+
>> module_put(fsa.owner);
>> preempt_enable();
>> }
>>--
>>2.7.4
>>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Re: [PATCH] kernel/module: Use BUG_ON instead of if condition followed by BUG.
2021-04-13 7:21 ` 周传高
@ 2021-04-13 12:42 ` Jessica Yu
0 siblings, 0 replies; 4+ messages in thread
From: Jessica Yu @ 2021-04-13 12:42 UTC (permalink / raw)
To: 周传高; +Cc: linux-kernel
+++ 周传高 [13/04/21 15:21 +0800]:
>
>>+++ zhouchuangao [30/03/21 05:07 -0700]:
>>>It can be optimized at compile time.
>>>
>>>Signed-off-by: zhouchuangao <zhouchuangao@vivo.com>
>>
>>Hi,
>>
>>Could you please provide a more descriptive changelog? I.e., Is this
>>a fix for a cocinelle warning? What are the optimization(s)?
>>
>>Thanks,
>>
>First,
>This patch comes from cocinelle warning.
>
>Second,
>#define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
>
>BUG_ON uses unlikely in if(). Through disassembly, we can see that
>brk #0x800 is compiled to the end of the function.
>As you can see below:
> ......
> ffffff8008660bec: d65f03c0 ret
> ffffff8008660bf0: d4210000 brk #0x800
>
>Usually, the condition in if () is not satisfied. For the multi-stage pipeline,
>we do not need to perform fetch decode and excute operation on brk
>instruction.
>
>In my opinion, this can improve the efficiency of the multi-stage pipeline.
Thanks. Could you please modify your commit/changelog message to
include this information (including the coccinelle warning) and resend
the patch?
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-03-30 12:07 [PATCH] kernel/module: Use BUG_ON instead of if condition followed by BUG zhouchuangao
2021-04-12 13:04 ` Jessica Yu
2021-04-13 7:21 ` 周传高
2021-04-13 12:42 ` Jessica Yu
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