linux-kernel - Re: [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp

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Message-ID: <ZC1qInkK7jt/YJXc@lothringen>
Date:   Wed, 5 Apr 2023 14:31:30 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Yair Podemsky <ypodemsk@...hat.com>, linux@...linux.org.uk,
        mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
        hca@...ux.ibm.com, gor@...ux.ibm.com, agordeev@...ux.ibm.com,
        borntraeger@...ux.ibm.com, svens@...ux.ibm.com,
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Subject: Re: [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI
 only to CPUs in kernel mode

On Wed, Apr 05, 2023 at 02:05:13PM +0200, Frederic Weisbecker wrote:
> On Wed, Apr 05, 2023 at 01:41:48PM +0200, Peter Zijlstra wrote:
> 1) It has the advantage to check context tracking _after_ the llist_add(), so
>    it really can't be misused ordering-wise.
> 
> 2) The IPI callback is always enqueued and then executed upon return
>    from userland. The ordering makes sure it will either IPI or execute
>    upon return to userspace.

*from userspace