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Date: Wed, 18 Jan 2012 10:51:49 -0500 (EST) From: Alan Stern <stern@...land.harvard.edu> To: Greg KH <gregkh@...e.de> cc: Ingo Molnar <mingo@...e.hu>, Linus Torvalds <torvalds@...ux-foundation.org>, "Rafael J. Wysocki" <rjw@...k.pl>, "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>, Sergei Trofimovich <slyich@...il.com>, <linux-kernel@...r.kernel.org>, Kay Sievers <kay.sievers@...y.org>, Linux PM mailing list <linux-pm@...r.kernel.org>, Tony Luck <tony.luck@...el.com>, Borislav Petkov <bp@...64.org>, "tglx@...utronix.de" <tglx@...utronix.de>, <prasad@...ux.vnet.ibm.com>, Ming Lei <tom.leiming@...il.com>, Djalal Harouni <tixxdz@...ndz.org>, Borislav Petkov <borislav.petkov@....com>, Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>, Andi Kleen <ak@...ux.intel.com>, <gouders@...bocholt.fh-gelsenkirchen.de>, Marcos Souza <marcos.mage@...il.com>, <justinmattock@...il.com>, Jeff Chua <jeff.chua.linux@...il.com> Subject: Re: [PATCH] mce: fix warning messages about static struct mce_device On Wed, 18 Jan 2012, Greg KH wrote: > > > > Minor nit, i don't think we have any other such [CONFIG_NR_CPUS] > > > > pattern in the kernel. > > > > > > > > This should be something like: > > > > > > > > DECLARE_PER_CPU(struct device *, mce_device); > > > > > > That is what we used to have, but with just a static struct > > > device. [...] Ingo's suggestion is fine. The difference is that instead of a static array of struct device's, this is a static pre-cpu pointer to a dynamic struct device (effectively, an array of pointers rather than an array of structures). > > Which was fine in itself for a per CPU data structure - wouldnt > > the warning be fixed by memset()-ing before registering the > > device or such, if device registry absolutely needs a pre-zeroed > > buffer? > > It was already fixed that way, but the problem is that you can not have > statically allocated 'struct device' objects in the system. That's what > my add-on patch fixed, also resolving the syslog messages saying there > was no release function for the device as well. > > > I still think there must be some bug/assumption lurking in the > > device layer - do you require all device allocations to be one > > via zalloc()? Seems like a weird and unrobust requirement. > > Yes, that's always been the requirement. There's an additional requirement: Device structures may not be reused. Not even if the caller clears all the fields to 0 in between. That was the real bug in the original code -- and adding a dummy release routine wouldn't fix it. > > Amongst other things we use PER_CPU to have an array of just 2 > > elements on a dual core system, even if it boots a > > CONFIG_NR_CPUS=512 distro kernel. That saves RAM, and with > > higher CONFIG_NR_CPUS values it adds up quickly. > > > > > > Or the pointer should be attached to the CPU info structure. > > > > > > Ok, I have no objection to that, do you want me to make a > > > patch doing that, now that this is already in Linus's tree? > > > > Would be nice if you could do that or some other equivalent > > solution, i'd really not like to see the [CONFIG_NR_CPUS] > > pattern to spread in the kernel, we spent a lot of time getting > > rid of such uses ;-) > > Ok, I'll work on resolving this. A static per-cpu pointer to struct device should work perfectly. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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