cpumask: Use all NR_CPUS bits unless CONFIG_CPUMASK_OFFSTACK (7be75853) · Commits · 戴 / test

Impact: futureproof as we convert more code to new APIs The old cpumask operators treat all NR_CPUS bits as relevent, the new ones use nr_cpumask_bits. For large NR_CPUS and small nr_cpu_ids, this makes a difference. However, mixing the two can cause problems with undefined bits. An arch which sets CONFIG_CPUMASK_OFFSTACK should have converted across to the new operators, so it's safe in that case. (Thanks to Stephen Rothwell for bisecting the initial unused-bits bug, and Mike Travis for this solution). Signed-off-by:

Rusty Russell <rusty@rustcorp.com.au> Cc: Mike Travis <travis@sgi.com>

include/linux/cpumask.h

+7 −4

Original line number	Diff line number	Diff line
		@@ -510,9 +510,6 @@ extern cpumask_t cpu_active_map;
		[BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD \
		}

		/* This produces more efficient code. */
		#define nr_cpumask_bits NR_CPUS

		#else /* NR_CPUS > BITS_PER_LONG */

		#define CPU_BITS_ALL \
		@@ -520,9 +517,15 @@ extern cpumask_t cpu_active_map;
		[0 ... BITS_TO_LONGS(NR_CPUS)-2] = ~0UL, \
		[BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD \
		}
		#endif /* NR_CPUS > BITS_PER_LONG */

		#ifdef CONFIG_CPUMASK_OFFSTACK
		/* Assuming NR_CPUS is huge, a runtime limit is more efficient. Also,
		* not all bits may be allocated. */
		#define nr_cpumask_bits nr_cpu_ids
		#endif /* NR_CPUS > BITS_PER_LONG */
		#else
		#define nr_cpumask_bits NR_CPUS
		#endif

		/* verify cpu argument to cpumask_* operators */
		static inline unsigned int cpumask_check(unsigned int cpu)

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