linux-kernel - Re: [patch 3.5-rc3] mm, mempolicy: fix mbind() to do synchronous migration

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Date:	Thu, 21 Jun 2012 20:59:07 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Rientjes <rientjes@...gle.com>, Mel Gorman <mgorman@...e.de>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [patch 3.5-rc3] mm, mempolicy: fix mbind() to do synchronous migration

On Thu, Jun 21, 2012 at 8:33 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> I'll see what it looks like if I only warn about casting *to* an enum.

Hmm. That results in much fewer warnings. Not that I'm sure that my
sparse hack is right. But for my normal build (which is pretty
minimal), I get:

    drivers/ata/libahci.c:1786:16: warning: casting to an enum type
    drivers/ata/libata-sff.c:1662:16: warning: casting to an enum type
    drivers/gpu/drm/i915/i915_irq.c:2300:16: warning: casting to an enum type
    drivers/gpu/drm/i915/i915_irq.c:2544:16: warning: casting to an enum type
    drivers/gpu/drm/i915/i915_irq.c:740:16: warning: casting to an enum type
    drivers/gpu/drm/i915/intel_panel.c:319:50: warning: casting to an enum type
    drivers/input/mouse/lifebook.c:148:59: warning: casting to an enum type
    drivers/input/mouse/lifebook.c:153:80: warning: casting to an enum type
    drivers/input/mouse/lifebook.c:156:59: warning: casting to an enum type
    drivers/input/mouse/lifebook.c:159:73: warning: casting to an enum type
    drivers/input/mouse/synaptics.c:1129:86: warning: casting to an enum type
    drivers/input/serio/i8042.c:533:16: warning: casting to an enum type
    drivers/input/serio/i8042.c:693:16: warning: casting to an enum type
    drivers/net/ethernet/realtek/r8169.c:5860:16: warning: casting to
an enum type
    drivers/pci/probe.c:511:26: warning: casting to an enum type
    drivers/tty/serial/8250/8250.c:1556:16: warning: casting to an enum type
    drivers/usb/host/xhci-ring.c:2419:24: warning: casting to an enum type
    fs/sysfs/sysfs.h:114:51: warning: casting to an enum type
    include/linux/mm.h:660:47: warning: casting to an enum type
    kernel/sched/rt.c:32:21: warning: casting to an enum type
    kernel/time/alarmtimer.c:231:16: warning: casting to an enum type
    kernel/time/alarmtimer.c:439:16: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1035:13: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1041:13: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1044:5: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1045:30: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1138:21: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1140:5: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1141:30: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1233:25: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1262:5: warning: casting to an enum type
    lib/zlib_deflate/deflate.c:1263:30: warning: casting to an enum type
    net/ipv4/ipmr.c:449:24: warning: casting to an enum type
    net/ipv4/netfilter/nf_defrag_ipv4.c:58:47: warning: casting to an enum type
    net/ipv4/netfilter/nf_defrag_ipv4.c:60:48: warning: casting to an enum type
    net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:49:48: warning: casting
to an enum type
    net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:51:49: warning: casting
to an enum type
    sound/pci/intel8x0.c:821:24: warning: casting to an enum type

but the ones I looked at were all ok. Admittedly I only looked at a
few (maybe five), though.

That said, the drivers/pci/probe.c case is actually ugly code. That
"agp_speeds[]" array *could* be an array of the proper enum's, rather
than "unsigned char". I don't know why it isn't (but 'unsigned char'
may be more efficient than a compiler that might make it an 'int').

So the warning *may* be useful. However, to get sparse to give that
warning I had to do some hacks that broke other parts of sparse, so I
don't have a good sparse patch yet. I'll look at it some more
tomorrow.

               Linus
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