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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2007-10-16 23:25:42 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-17 08:42:44 -0700
commit3cb4f9fa0c5f3ded9f70f85b70ee6d429834f911 (patch)
treed1f45445fa98bd41a2f8986781f7c62b470a6b8d /include/linux
parentaa0dff2d09bfa50b7d02714a45920c64568e699d (diff)
lib: percpu_counter_sub
Hugh spotted that some code does: percpu_counter_add(&counter, -unsignedlong) which, when the amount argument is of type s32, sort-of works thanks to two's-complement. However when we'd change the type to s64 this breaks on 32bit machines, because the promotion rules zero extend the unsigned number. Provide percpu_counter_sub() to hide the s64 cast. That is: percpu_counter_sub(&counter, foo) is equal to: percpu_counter_add(&counter, -(s64)foo); Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/percpu_counter.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
index b84fc8667de..438a170187e 100644
--- a/include/linux/percpu_counter.h
+++ b/include/linux/percpu_counter.h
@@ -105,4 +105,9 @@ static inline void percpu_counter_dec(struct percpu_counter *fbc)
percpu_counter_add(fbc, -1);
}
+static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
+{
+ percpu_counter_add(fbc, -amount);
+}
+
#endif /* _LINUX_PERCPU_COUNTER_H */