Messages in this thread | | | Date | Tue, 15 Jul 2008 14:14:29 -0700 | From | Mike Travis <> | Subject | [PATCH 0/8] cpumask: Replace/optimize cpumask_of_cpu & cpumask_t operations |
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> From Rusty Russell <rusty@rustcorp.com.au>: > > Hi Christoph/Mike, > > Looked at cpumask_of_cpu as introduced in > 9f0e8d0400d925c3acd5f4e01dbeb736e4011882 (x86: convert cpumask_of_cpu > macro to allocated array), and I don't think it's safe: > > #define cpumask_of_cpu(cpu) \ > (*({ \ > typeof(_unused_cpumask_arg_) m; \ > if (sizeof(m) == sizeof(unsigned long)) { \ > m.bits[0] = 1UL<<(cpu); \ > } else { \ > cpus_clear(m); \ > cpu_set((cpu), m); \ > } \ > &m; \ > })) > > Referring to &m once out of scope is invalid, and I can't find any > evidence that it's legal here. In particular, the change > b53e921ba1cff8453dc9a87a84052fa12d5b30bd (generic: reduce stack pressure > in sched_affinity) which passes &m to other functions seems highly risky.
* Patch 1 replaces the dangerous lvalue version of cpumask_of_cpu with new cpumask_of_cpu_ptr macros. These are patterned after the node_to_cpumask_ptr macros.
* Patches 2..6 optimizes various places where a pointer to the cpumask_of_cpu value will result in reducing stack pressure.
* Patch 7 provides a generic set of CPUMASK_ALLOC macros patterned after the SCHED_CPUMASK_ALLOC macros. This is used where multiple cpumask_t variables are declared on the stack to reduce the amount of stack space required.
* Patch 8 uses the CPUMASK_ALLOC macros in the centrino_target() function.
Based on linux-2.6.tip/master at the following commit:
commit 0a91813e16ebd5c2d9b5c2acd5b7c91742112c4f Merge: 9a635fa... 724dce0... Author: Ingo Molnar <mingo@elte.hu> Date: Tue Jul 15 14:55:17 2008 +0200
Signed-off-by: Mike Travis <travis@sgi.com> Cc: Tigran Aivazian <tigran@aivazian.fsnet.co.uk> Cc: Greg Banks <gnb@sgi.com> Cc: Len Brown <len.brown@intel.com> Cc: Adrian Bunk <bunk@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Paul Jackson <pj@sgi.com> Cc: Dave Jones <davej@codemonkey.org.uk> Cc: Dean Nelson <dcn@sgi.com> Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com> Cc: Robert Richter <robert.richter@amd.com> Cc: Eric W. Biederman <ebiederm@xmission.com> ---
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