linux-kernel - Re: [PATCH v2 01/24] lockdep: Fix might

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Message-ID: <c633b429-0ad4-4b92-942c-0338a9801cb2@redhat.com>
Date: Thu, 6 Feb 2025 19:19:43 +0100
From: David Hildenbrand <david@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
 ravi.bangoria@....com, lucas.demarchi@...el.com
Cc: linux-kernel@...r.kernel.org, willy@...radead.org, acme@...nel.org,
 namhyung@...nel.org, mark.rutland@....com,
 alexander.shishkin@...ux.intel.com, jolsa@...nel.org, irogers@...gle.com,
 adrian.hunter@...el.com, kan.liang@...ux.intel.com
Subject: Re: [PATCH v2 01/24] lockdep: Fix might_fault()

On 05.02.25 11:21, Peter Zijlstra wrote:
> Turns out that commit 9ec23531fd48 ("sched/preempt, mm/fault: Trigger
> might_sleep() in might_fault() with disabled pagefaults") accidentally
> (and unnessecarily) put the lockdep part of __might_fault() under
> CONFIG_DEBUG_ATOMIC_SLEEP.
> 
> Cc: David Hildenbrand <david@...hat.com>
> Fixes: 9ec23531fd48 ("sched/preempt, mm/fault: Trigger might_sleep() in might_fault() with disabled pagefaults")

Heh, that was 10 years ago, part one of my first not-kvm-specific patch 
series.

Very likely it was not by accident, but I don't have any memory on that 
part :)

Probably I actually wanted this to be

  #if defined(CONFIG_PROVE_LOCKING)

such that the function looked more similar to pre-662bbcb2747c


> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>   mm/memory.c |    2 --
>   1 file changed, 2 deletions(-)
> 
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -6695,10 +6695,8 @@ void __might_fault(const char *file, int
>   	if (pagefault_disabled())
>   		return;
>   	__might_sleep(file, line);
> -#if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
>   	if (current->mm)
>   		might_lock_read(&current->mm->mmap_lock);
> -#endif
>   }
>   EXPORT_SYMBOL(__might_fault);
>   #endif
> 
> 


-- 
Cheers,

David / dhildenb