linux-kernel - Re: [PATCH 03/24] arc: use asm-generic/mmu

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Message-ID: <04b9872c-e9d8-2221-0bf6-595dbd15d8eb@synopsys.com>
Date:   Tue, 28 Jul 2020 03:58:25 +0000
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Nicholas Piggin <npiggin@...il.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Arnd Bergmann <arnd@...db.de>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH 03/24] arc: use asm-generic/mmu_context.h for no-op
 implementations

On 7/27/20 8:33 PM, Nicholas Piggin wrote:

>  /*
> - * Called at the time of execve() to get a new ASID
> - * Note the subtlety here: get_new_mmu_context() behaves differently here
> - * vs. in switch_mm(). Here it always returns a new ASID, because mm has
> - * an unallocated "initial" value, while in latter, it moves to a new ASID,
> - * only if it was unallocated
> + * activate_mm defaults to switch_mm and is called at the time of execve() to

With activate_mm() definition actually gone, perhaps add "activate_mm() comes from
generic code..." to provide next reader about the "spurious looking comment"

> + * get a new ASID Note the subtlety here: get_new_mmu_context() behaves
> + * differently here vs. in switch_mm(). Here it always returns a new ASID,
> + * because mm has an unallocated "initial" value, while in latter, it moves to
> + * a new ASID, only if it was unallocated
>   */
> -#define activate_mm(prev, next)		switch_mm(prev, next, NULL)
>  
>  /* it seemed that deactivate_mm( ) is a reasonable place to do book-keeping
>   * for retiring-mm. However destroy_context( ) still needs to do that because
> @@ -168,8 +169,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
>   * there is a good chance that task gets sched-out/in, making it's ASID valid
>   * again (this teased me for a whole day).
>   */
> -#define deactivate_mm(tsk, mm)   do { } while (0)

same for deactivate_mm()