linux-kernel - Re: [PATCH v2] cma_alloc(), indefinitely retry allocations for -EBUSY failures

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Date:   Fri, 11 Sep 2020 21:29:38 +0000
From:   Chris Goldsworthy <cgoldswo@...eaurora.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-kernel-owner@...r.kernel.org
Subject: Re: [PATCH v2] cma_alloc(), indefinitely retry allocations for -EBUSY
 failures

On 2020-09-11 13:54, Chris Goldsworthy wrote:
> [PATCH v2] cma_alloc(), indefinitely retry allocations for -EBUSY 
> failures
> 
> On mobile devices, failure to allocate from a CMA area constitutes a
> functional failure.  Sometimes during CMA allocations, we have observed
> that pages in a CMA area allocated through alloc_pages(), that we're 
> trying
> to migrate away to make room for a CMA allocation, are temporarily 
> pinned.
> This temporary pinning can occur when a process that owns the pinned 
> page
> is being forked (the example is explained further in the commit text), 
> or it is
> exiting.  This patch addresses this issue by indefinitely retrying 
> allocations
> that fail due to a return of -EBUSY.
> 
> ** This change log was re-sent due to threading issues **
> 
> Change log:
> 
> v1: We were performing retries of the allocation a fixed number of 
> times.
> Andrew Morton disliked this, as it didn't guarantee that the allocation 
> would
> succeed.
> 
> https://lkml.org/lkml/2020/8/5/1096
> https://lkml.org/lkml/2020/8/21/1490
> 
> v2: To address this concern, we switched to retrying indefinitely, as 
> opposed to
> doing to retrying  the allocation a limited number of times.
> 
> Chris Goldsworthy (1):
>   mm: cma: indefinitely retry allocations in cma_alloc
> 
>  mm/cma.c | 25 +++++++++++++++++++++++--
>  1 file changed, 23 insertions(+), 2 deletions(-)
test
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