From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Travis Subject: Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c - bisected Date: Tue, 26 Aug 2008 12:06:18 -0700 Message-ID: <48B4542A.1050004@sgi.com> References: <20080826072220.GB31876@elte.hu> <20080826.004607.253712060.davem@davemloft.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20080826.004607.253712060.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: David Miller Cc: mingo@elte.hu, torvalds@linux-foundation.org, Alan.Brunelle@hp.com, tglx@linutronix.de, rjw@sisk.pl, linux-kernel@vger.kernel.org, kernel-testers@vger.kernel.org, akpm@linux-foundation.org, arjan@linux.intel.com, rusty@rustcorp.com.au David Miller wrote: > From: Ingo Molnar > Date: Tue, 26 Aug 2008 09:22:20 +0200 > >> And i guess the next generation of 4K CPUs support should just get away >> from cpumask_t-on-kernel-stack model altogether, as the current model is >> not maintainable. We tried the on-kernel-stack variant, and it really >> does not work reliably. We can fix this in v2.6.28. > > I recently did some work on sparc64 to use cpumask pointers > as much as possible. > > The only case that didn't work was due to a limitation in > arch interfaces for the new generic smp_call_function() code. > It passes a cpumask_t instead of a pointer to one via > arch_send_call_function_ipi(). > > But other than that, the whole sparc64 SMP stuff uses cpumask_t > pointers only. > > What it comes down to is that you have to do the "self cpu" > and other tests in the cross-call dispatch routines themselves, > instead of at the top-level working on cpumask_t objects. > > Otherwise you have to modify cpumask_t objects and thus pluck > them onto the stack where they take up silly amounts of space. Yes, I had proposed either modifying, or supplementing a new smp_call function to pass the cpumask_t as a pointer (similar to set_cpus_allowed_ptr.) But an ABI change such as this was not well received at the time. Thanks, Mike