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Peter Anvin" , Sander Vanheule Subject: [PATCH v4 2/5] cpumask: Fix invalid uniprocessor mask assumption Date: Sat, 2 Jul 2022 18:08:25 +0200 Message-Id: <86bf3f005abba2d92120ddd0809235cab4f759a6.1656777646.git.sander@svanheule.net> X-Mailer: git-send-email 2.36.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On uniprocessor builds, any CPU mask is assumed to contain exactly one CPU (cpu0). This assumption ignores the existence of empty masks, resulting in incorrect behaviour. cpumask_first_zero(), cpumask_next_zero(), and for_each_cpu_not() don't provide behaviour matching the assumption that a UP mask is always "1", and instead provide behaviour matching the empty mask. Drop the incorrectly optimised code and use the generic implementations in all cases. Signed-off-by: Sander Vanheule --- Notes: Changes since v3: - Add back UP-optimised cpumask_local_spread, cpumask_any_distribute, cpumask_any_and_distribute Changes since v1: - Drop UP implementations instead of trying to fix them include/linux/cpumask.h | 99 ++++++++--------------------------------- lib/Makefile | 3 +- lib/cpumask.c | 2 + 3 files changed, 22 insertions(+), 82 deletions(-) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index fe29ac7cc469..7fbef41b3093 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -116,85 +116,6 @@ static __always_inline unsigned int cpumask_check(unsigned int cpu) return cpu; } -#if NR_CPUS == 1 -/* Uniprocessor. Assume all masks are "1". */ -static inline unsigned int cpumask_first(const struct cpumask *srcp) -{ - return 0; -} - -static inline unsigned int cpumask_first_zero(const struct cpumask *srcp) -{ - return 0; -} - -static inline unsigned int cpumask_first_and(const struct cpumask *srcp1, - const struct cpumask *srcp2) -{ - return 0; -} - -static inline unsigned int cpumask_last(const struct cpumask *srcp) -{ - return 0; -} - -/* Valid inputs for n are -1 and 0. */ -static inline unsigned int cpumask_next(int n, const struct cpumask *srcp) -{ - return n+1; -} - -static inline unsigned int cpumask_next_zero(int n, const struct cpumask *srcp) -{ - return n+1; -} - -static inline unsigned int cpumask_next_and(int n, - const struct cpumask *srcp, - const struct cpumask *andp) -{ - return n+1; -} - -static inline unsigned int cpumask_next_wrap(int n, const struct cpumask *mask, - int start, bool wrap) -{ - /* cpu0 unless stop condition, wrap and at cpu0, then nr_cpumask_bits */ - return (wrap && n == 0); -} - -/* cpu must be a valid cpu, ie 0, so there's no other choice. */ -static inline unsigned int cpumask_any_but(const struct cpumask *mask, - unsigned int cpu) -{ - return 1; -} - -static inline unsigned int cpumask_local_spread(unsigned int i, int node) -{ - return 0; -} - -static inline int cpumask_any_and_distribute(const struct cpumask *src1p, - const struct cpumask *src2p) { - return cpumask_first_and(src1p, src2p); -} - -static inline int cpumask_any_distribute(const struct cpumask *srcp) -{ - return cpumask_first(srcp); -} - -#define for_each_cpu(cpu, mask) \ - for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask) -#define for_each_cpu_not(cpu, mask) \ - for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask) -#define for_each_cpu_wrap(cpu, mask, start) \ - for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask, (void)(start)) -#define for_each_cpu_and(cpu, mask1, mask2) \ - for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask1, (void)mask2) -#else /** * cpumask_first - get the first cpu in a cpumask * @srcp: the cpumask pointer @@ -260,10 +181,29 @@ static inline unsigned int cpumask_next_zero(int n, const struct cpumask *srcp) int __pure cpumask_next_and(int n, const struct cpumask *, const struct cpumask *); int __pure cpumask_any_but(const struct cpumask *mask, unsigned int cpu); + +#if NR_CPUS == 1 +/* Uniprocessor: there is only one valid CPU */ +static inline unsigned int cpumask_local_spread(unsigned int i, int node) +{ + return 0; +} + +static inline int cpumask_any_and_distribute(const struct cpumask *src1p, + const struct cpumask *src2p) { + return cpumask_first_and(src1p, src2p); +} + +static inline int cpumask_any_distribute(const struct cpumask *srcp) +{ + return cpumask_first(srcp); +} +#else unsigned int cpumask_local_spread(unsigned int i, int node); int cpumask_any_and_distribute(const struct cpumask *src1p, const struct cpumask *src2p); int cpumask_any_distribute(const struct cpumask *srcp); +#endif /* NR_CPUS */ /** * for_each_cpu - iterate over every cpu in a mask @@ -324,7 +264,6 @@ extern int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool for ((cpu) = -1; \ (cpu) = cpumask_next_and((cpu), (mask1), (mask2)), \ (cpu) < nr_cpu_ids;) -#endif /* SMP */ #define CPU_BITS_NONE \ { \ diff --git a/lib/Makefile b/lib/Makefile index f99bf61f8bbc..bcc7e8ea0cde 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -34,10 +34,9 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \ is_single_threaded.o plist.o decompress.o kobject_uevent.o \ earlycpio.o seq_buf.o siphash.o dec_and_lock.o \ nmi_backtrace.o nodemask.o win_minmax.o memcat_p.o \ - buildid.o + buildid.o cpumask.o lib-$(CONFIG_PRINTK) += dump_stack.o -lib-$(CONFIG_SMP) += cpumask.o lib-y += kobject.o klist.o obj-y += lockref.o diff --git a/lib/cpumask.c b/lib/cpumask.c index a971a82d2f43..b9728513a4d4 100644 --- a/lib/cpumask.c +++ b/lib/cpumask.c @@ -192,6 +192,7 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask) } #endif +#if NR_CPUS > 1 /** * cpumask_local_spread - select the i'th cpu with local numa cpu's first * @i: index number @@ -279,3 +280,4 @@ int cpumask_any_distribute(const struct cpumask *srcp) return next; } EXPORT_SYMBOL(cpumask_any_distribute); +#endif /* NR_CPUS */ -- 2.36.1