linux-kernel - Re: [PATCH] arm64: Return early when break handler is found on linked-list

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Message-ID: <d5f964b4-f59d-d16a-3278-9fd374df554a@huawei.com>
Date: Thu, 29 Aug 2024 11:29:16 +0800
From: "Liao, Chang" <liaochang1@...wei.com>
To: Will Deacon <will@...nel.org>
CC: <catalin.marinas@....com>, <ptosi@...gle.com>, <oliver.upton@...ux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: Return early when break handler is found on
 linked-list



在 2024/8/27 20:30, Will Deacon 写道:
> On Tue, Aug 27, 2024 at 11:00:46AM +0000, Liao Chang wrote:
>> The search for breakpoint handlers iterate through the entire
>> linked list. Given that all registered hook has a valid fn field, and no
>> registered hooks share the same mask and imm. This commit optimize the
>> efficiency slightly by returning early as a matching handler is found.
>>
>> Signed-off-by: Liao Chang <liaochang1@...wei.com>
>> ---
>>  arch/arm64/kernel/debug-monitors.c | 7 ++++---
>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
>> index 024a7b245056..fc998956f44c 100644
>> --- a/arch/arm64/kernel/debug-monitors.c
>> +++ b/arch/arm64/kernel/debug-monitors.c
>> @@ -281,6 +281,7 @@ static LIST_HEAD(kernel_break_hook);
>>  
>>  void register_user_break_hook(struct break_hook *hook)
>>  {
>> +	WARN_ON(!hook->fn);
>>  	register_debug_hook(&hook->node, &user_break_hook);
>>  }
>>  
>> @@ -291,6 +292,7 @@ void unregister_user_break_hook(struct break_hook *hook)
>>  
>>  void register_kernel_break_hook(struct break_hook *hook)
>>  {
>> +	WARN_ON(!hook->fn);
>>  	register_debug_hook(&hook->node, &kernel_break_hook);
>>  }
> 
> I don't think we need these WARN_ON()s. This API is pretty limited and
> passing a NULL callback doesn't make sense.

Them will be removed in next revision.

> 
> Rest of the patch looks fine.
> 
> Will
> 
> 

-- 
BR
Liao, Chang