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From: Mel Gorman <mgorman@techsingularity.net>
To: Matt Fleming <matt@codeblueprint.co.uk>
Cc: "Dave Young" <dyoung@redhat.com>,
	"Nicolai Stange" <nicstange@gmail.com>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, linux-efi@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"Mika Penttilä" <mika.penttila@nextfour.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-mm@kvack.org, "Vlastimil Babka" <vbabka@suse.cz>,
	"Michal Hocko" <mhocko@suse.cz>
Subject: Re: [PATCH v2 2/2] efi: efi_mem_reserve(): don't reserve through memblock after mm_init()
Date: Mon, 9 Jan 2017 13:31:52 +0000	[thread overview]
Message-ID: <20170109133152.2izkcrzgzinxdwux@techsingularity.net> (raw)
In-Reply-To: <20170109114400.GF16838@codeblueprint.co.uk>

On Mon, Jan 09, 2017 at 11:44:00AM +0000, Matt Fleming wrote:
> On Thu, 05 Jan, at 05:12:42PM, Dave Young wrote:
> > On 12/22/16 at 11:23am, Nicolai Stange wrote:
> > > Before invoking the arch specific handler, efi_mem_reserve() reserves
> > > the given memory region through memblock.
> > > 
> > > efi_mem_reserve() can get called after mm_init() though -- through
> > > efi_bgrt_init(), for example. After mm_init(), memblock is dead and should
> > > not be used anymore.
> > 
> > It did not fail during previous test so we did not catch this bug, if memblock
> > can not be used after mm_init(), IMHO it should fail instead of silently succeed.
>  
> This must literally be the fifth time or so that I've been caught out
> by this over the years because there's no hard error if you call the
> memblock code after slab and co. are up.
> 
> MM folks, is there some way to catch these errors without requiring
> the sprinkling of slab_is_available() everywhere?
> 

Well, you could put in a __init global variable about availability into
mm/memblock.c and then check it in memblock APIs like memblock_reserve()
to BUG_ON? I know BUG_ON is frowned upon but this is not likely to be a
situation that can be sensibly recovered.

-- 
Mel Gorman
SUSE Labs

WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@techsingularity.net>
To: Matt Fleming <matt@codeblueprint.co.uk>
Cc: "Dave Young" <dyoung@redhat.com>,
	"Nicolai Stange" <nicstange@gmail.com>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, linux-efi@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"Mika Penttilä" <mika.penttila@nextfour.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-mm@kvack.org, "Vlastimil Babka" <vbabka@suse.cz>,
	"Michal Hocko" <mhocko@suse.cz>
Subject: Re: [PATCH v2 2/2] efi: efi_mem_reserve(): don't reserve through memblock after mm_init()
Date: Mon, 9 Jan 2017 13:31:52 +0000	[thread overview]
Message-ID: <20170109133152.2izkcrzgzinxdwux@techsingularity.net> (raw)
In-Reply-To: <20170109114400.GF16838@codeblueprint.co.uk>

On Mon, Jan 09, 2017 at 11:44:00AM +0000, Matt Fleming wrote:
> On Thu, 05 Jan, at 05:12:42PM, Dave Young wrote:
> > On 12/22/16 at 11:23am, Nicolai Stange wrote:
> > > Before invoking the arch specific handler, efi_mem_reserve() reserves
> > > the given memory region through memblock.
> > > 
> > > efi_mem_reserve() can get called after mm_init() though -- through
> > > efi_bgrt_init(), for example. After mm_init(), memblock is dead and should
> > > not be used anymore.
> > 
> > It did not fail during previous test so we did not catch this bug, if memblock
> > can not be used after mm_init(), IMHO it should fail instead of silently succeed.
>  
> This must literally be the fifth time or so that I've been caught out
> by this over the years because there's no hard error if you call the
> memblock code after slab and co. are up.
> 
> MM folks, is there some way to catch these errors without requiring
> the sprinkling of slab_is_available() everywhere?
> 

Well, you could put in a __init global variable about availability into
mm/memblock.c and then check it in memblock APIs like memblock_reserve()
to BUG_ON? I know BUG_ON is frowned upon but this is not likely to be a
situation that can be sensibly recovered.

-- 
Mel Gorman
SUSE Labs

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  reply	other threads:[~2017-01-09 13:32 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-22 10:23 [PATCH v2 1/2] x86/efi: don't allocate memmap through memblock after mm_init() Nicolai Stange
2016-12-22 10:23 ` Nicolai Stange
2016-12-22 10:23 ` [PATCH v2 2/2] efi: efi_mem_reserve(): don't reserve " Nicolai Stange
2017-01-05  9:12   ` Dave Young
2017-01-05  9:12     ` Dave Young
2017-01-09 11:44     ` Matt Fleming
2017-01-09 11:44       ` Matt Fleming
2017-01-09 13:31       ` Mel Gorman [this message]
2017-01-09 13:31         ` Mel Gorman
2017-01-09 13:45         ` Matt Fleming
2017-01-09 13:45           ` Matt Fleming
2017-02-27 21:57         ` Matt Fleming
2017-02-27 21:57           ` Matt Fleming
2017-02-27 21:57           ` Matt Fleming
2017-01-10  0:37       ` Dave Young
2017-01-10  0:37         ` Dave Young
2017-01-10 12:51         ` Matt Fleming
2017-01-10 12:51           ` Matt Fleming
2017-01-11  8:04           ` Dave Young
2017-01-11  8:04             ` Dave Young
2016-12-23 14:52 ` [PATCH v2 1/2] x86/efi: don't allocate memmap " Matt Fleming
2016-12-23 21:12   ` Nicolai Stange
2017-01-05  7:42     ` Ingo Molnar
2017-01-05  7:42       ` Ingo Molnar
2017-01-05  9:15       ` Dave Young
2017-01-05  9:15         ` Dave Young
2017-01-05  9:39       ` Ard Biesheuvel
2017-01-05 10:15         ` Nicolai Stange
2017-01-05 10:15           ` Nicolai Stange
2017-01-05 11:34           ` Ard Biesheuvel
2017-01-05 11:34             ` Ard Biesheuvel
2017-01-05 12:53             ` Nicolai Stange
2017-01-05 12:53               ` Nicolai Stange
2017-01-04 18:40 ` Dan Williams
2017-01-04 18:40   ` Dan Williams

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