The patch titled
Subject: cpumask: Fix invalid uniprocessor mask assumption
has been added to the -mm mm-nonmm-unstable branch. Its filename is
cpumask-fix-invalid-uniprocessor-mask-assumption.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/cpumask-fix-invalid-uniprocessor-mask-assumption.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sander Vanheule <sander@xxxxxxxxxxxxx>
Subject: cpumask: Fix invalid uniprocessor mask assumption
Date: Sat, 2 Jul 2022 18:08:25 +0200
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.
Link: https://lkml.kernel.org/r/86bf3f005abba2d92120ddd0809235cab4f759a6.1656777646.git.sander@xxxxxxxxxxxxx
Signed-off-by: Sander Vanheule <sander@xxxxxxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Yury Norov <yury.norov@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/cpumask.h | 99 +++++++-------------------------------
lib/Makefile | 3 -
lib/cpumask.c | 2
3 files changed, 22 insertions(+), 82 deletions(-)
--- a/include/linux/cpumask.h~cpumask-fix-invalid-uniprocessor-mask-assumption
+++ a/include/linux/cpumask.h
@@ -116,85 +116,6 @@ static __always_inline unsigned int cpum
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_
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, cons
for ((cpu) = -1; \
(cpu) = cpumask_next_and((cpu), (mask1), (mask2)), \
(cpu) < nr_cpu_ids;)
-#endif /* SMP */
#define CPU_BITS_NONE \
{ \
--- a/lib/cpumask.c~cpumask-fix-invalid-uniprocessor-mask-assumption
+++ a/lib/cpumask.c
@@ -192,6 +192,7 @@ void __init free_bootmem_cpumask_var(cpu
}
#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
return next;
}
EXPORT_SYMBOL(cpumask_any_distribute);
+#endif /* NR_CPUS */
--- a/lib/Makefile~cpumask-fix-invalid-uniprocessor-mask-assumption
+++ a/lib/Makefile
@@ -35,10 +35,9 @@ lib-y := ctype.o string.o vsprintf.o cmd
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
_
Patches currently in -mm which might be from sander@xxxxxxxxxxxxx are
x86-cacheinfo-move-shared-cache-map-definitions.patch
cpumask-fix-invalid-uniprocessor-mask-assumption.patch
lib-test-introduce-cpumask-kunit-test-suite.patch
cpumask-add-up-optimised-for_each__cpu-versions.patch
cpumask-update-cpumask_next_wrap-signature.patch
