linux-kernel - Re: [PATCH] mm/memprofiling: explicitly include irqflags.h in alloc

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Date: Sun, 7 Apr 2024 19:12:04 +0200
From: Klara Modin <klarasmodin@...il.com>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: akpm@...ux-foundation.org, surenb@...gle.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/memprofiling: explicitly include irqflags.h in
 alloc_tag.h



On 2024-04-07 19:01, Kent Overstreet wrote:
> On Sun, Apr 07, 2024 at 03:32:52PM +0200, Klara Modin wrote:
>> linux/alloc_tag.h uses the macro this_cpu_inc which eventually expands to:
>>
>>   #define this_cpu_generic_to_op(pcp, val, op)				\
>>   do {									\
>>   	unsigned long __flags;						\
>>   	raw_local_irq_save(__flags);					\
>>   	raw_cpu_generic_to_op(pcp, val, op);				\
>>   	raw_local_irq_restore(__flags);					\
>>   } while (0)
>>
>> The macros raw_local_irq_save and raw_local_irq_restore are defined in
>> linux/irqflags.h which is not included implicitly on all configs.
>> Therefore, include it explicitly.
>>
>> Fixes: ac906a377c67 ("lib: add allocation tagging support for memory allocation profiling")
>> Link: https://lore.kernel.org/lkml/6b8149f3-80e6-413c-abcb-1925ecda9d8c@gmail.com/
>> Signed-off-by: Klara Modin <klarasmodin@...il.com>
>> ---
>>   include/linux/alloc_tag.h | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
>> index e867461585ff..afc9e259a2d3 100644
>> --- a/include/linux/alloc_tag.h
>> +++ b/include/linux/alloc_tag.h
>> @@ -12,6 +12,7 @@
>>   #include <asm/percpu.h>
>>   #include <linux/cpumask.h>
>>   #include <linux/static_key.h>
>> +#include <linux/irqflags.h>
> 
> Actually, shouldn't this end up in a percpu header? Or was there a
> problem with that?

If I understand it correctly, linux/alloc_tag.h does not include 
linux/percpu.h (which has that include) to avoid a circular dependency 
as linux/percpu.h includes linux/alloc_tag.h. It instead includes 
arch-specific asm/percpu.h, and as a consequence it doesn't always get 
linux/irqflags.h.

It's also entirely possible that I've mixed something up, I really don't 
have much experience developing for the kernel.