linux-kernel - Re: [PATCH] x86/platform/uv: move kmalloc() NULL check routine

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Message-ID: <20190906104341.GW2349@hirez.programming.kicks-ass.net>
Date:   Fri, 6 Sep 2019 12:43:41 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Austin Kim <austindh.kim@...il.com>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        dvhart@...radead.org, andy@...radead.org, hpa@...or.com,
        allison@...utok.net, armijn@...ldur.nl, kjlu@....edu,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/platform/uv: move kmalloc() NULL check routine

On Fri, Sep 06, 2019 at 11:32:52AM +0200, Greg KH wrote:
> On Fri, Sep 06, 2019 at 08:29:51AM +0900, Austin Kim wrote:
> > The result of kmalloc should have been checked ahead of below statement:
> > 	pqp = (struct bau_pq_entry *)vp;
> > 
> > Move BUG_ON(!vp) before above statement.
> > 
> > Signed-off-by: Austin Kim <austindh.kim@...il.com>
> > ---
> >  arch/x86/platform/uv/tlb_uv.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
> > index 20c389a..5f0a96bf 100644
> > --- a/arch/x86/platform/uv/tlb_uv.c
> > +++ b/arch/x86/platform/uv/tlb_uv.c
> > @@ -1804,9 +1804,9 @@ static void pq_init(int node, int pnode)
> >  
> >  	plsize = (DEST_Q_SIZE + 1) * sizeof(struct bau_pq_entry);
> >  	vp = kmalloc_node(plsize, GFP_KERNEL, node);
> > -	pqp = (struct bau_pq_entry *)vp;
> > -	BUG_ON(!pqp);
> > +	BUG_ON(!vp);
> 
> Ick!  Don't crash the whole machine if you are out of memory, that's a
> totally lazy and broken driver.  Fix this up properly please.

This is boot time init; if memory allocation fails, we're in trouble, no
way forward no way back.

It is not uncommon to have BUG_ON() for alloc failing during boot.

> But the original code is just fine (from a this is doing what I want it
> to do point of view), I don't see the need to change anything here, you
> did not modify any logic at all.

Agreed, the patch seems entirely pointless.