sched: properly define the sched_group::cpumask and sched_domain::span fields
Properly document the variable-size structure tricks we are doing
wrt. struct sched_group and sched_domain, and use the field[0] GCC
extension instead of defining a vla array.
Dont use unions for this, as pointed out by Linus.
[ Impact: cleanup, un-confuse Sparse and LLVM ]
Reported-by: Jeff Garzik <jeff@garzik.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <alpine.LFD.2.01.0905180850110.3301@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index de7b3b2..dbb1043 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -839,7 +839,17 @@
*/
u32 reciprocal_cpu_power;
- unsigned long cpumask[];
+ /*
+ * The CPUs this group covers.
+ *
+ * NOTE: this field is variable length. (Allocated dynamically
+ * by attaching extra space to the end of the structure,
+ * depending on how many CPUs the kernel has booted up with)
+ *
+ * It is also be embedded into static data structures at build
+ * time. (See 'struct static_sched_group' in kernel/sched.c)
+ */
+ unsigned long cpumask[0];
};
static inline struct cpumask *sched_group_cpus(struct sched_group *sg)
@@ -925,8 +935,17 @@
char *name;
#endif
- /* span of all CPUs in this domain */
- unsigned long span[];
+ /*
+ * Span of all CPUs in this domain.
+ *
+ * NOTE: this field is variable length. (Allocated dynamically
+ * by attaching extra space to the end of the structure,
+ * depending on how many CPUs the kernel has booted up with)
+ *
+ * It is also be embedded into static data structures at build
+ * time. (See 'struct static_sched_domain' in kernel/sched.c)
+ */
+ unsigned long span[0];
};
static inline struct cpumask *sched_domain_span(struct sched_domain *sd)