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Subject[tip:sched/urgent] sched: avoid flexible array member inside struct (gcc extension)
Commit-ID:  61a7bca8b5c277ba35e58009e23a1e582f6748eb
Gitweb: http://git.kernel.org/tip/61a7bca8b5c277ba35e58009e23a1e582f6748eb
Author: Rusty Russell <rusty@rustcorp.com.au>
AuthorDate: Wed, 13 May 2009 16:19:12 +0930
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 13 May 2009 15:17:05 +0200

sched: avoid flexible array member inside struct (gcc extension)

struct sched_group and struct sched_domain end in 'unsigned long
cpumask[]' which Jeff Garzik notes is not legal C to place inside
another struct. It upsets sparse and clang (LLVM's C front end).

Al Viro pointed out that a union is the Right Way to do this.

[ Impact: use more standard C code ]

Reported-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Jeff Garzik <jeff@garzik.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
LKML-Reference: <200905131619.12880.rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
kernel/sched.c | 28 +++++++++++++++-------------
1 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 26efa47..d1ef62c 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7756,22 +7756,24 @@ int sched_smt_power_savings = 0, sched_mc_power_savings = 0;
* FIXME: use cpumask_var_t or dynamic percpu alloc to avoid wasting space
* for nr_cpu_ids < CONFIG_NR_CPUS.
*/
-struct static_sched_group {
+union static_sched_group {
struct sched_group sg;
- DECLARE_BITMAP(cpus, CONFIG_NR_CPUS);
+ char _sg_and_cpus[sizeof(struct sched_group) +
+ BITS_TO_LONGS(CONFIG_NR_CPUS) * sizeof(long)];
};

-struct static_sched_domain {
+union static_sched_domain {
struct sched_domain sd;
- DECLARE_BITMAP(span, CONFIG_NR_CPUS);
+ char _sd_and_cpus[sizeof(struct sched_domain) +
+ BITS_TO_LONGS(CONFIG_NR_CPUS) * sizeof(long)];
};

/*
* SMT sched-domains:
*/
#ifdef CONFIG_SCHED_SMT
-static DEFINE_PER_CPU(struct static_sched_domain, cpu_domains);
-static DEFINE_PER_CPU(struct static_sched_group, sched_group_cpus);
+static DEFINE_PER_CPU(union static_sched_domain, cpu_domains);
+static DEFINE_PER_CPU(union static_sched_group, sched_group_cpus);

static int
cpu_to_cpu_group(int cpu, const struct cpumask *cpu_map,
@@ -7787,8 +7789,8 @@ cpu_to_cpu_group(int cpu, const struct cpumask *cpu_map,
* multi-core sched-domains:
*/
#ifdef CONFIG_SCHED_MC
-static DEFINE_PER_CPU(struct static_sched_domain, core_domains);
-static DEFINE_PER_CPU(struct static_sched_group, sched_group_core);
+static DEFINE_PER_CPU(union static_sched_domain, core_domains);
+static DEFINE_PER_CPU(union static_sched_group, sched_group_core);
#endif /* CONFIG_SCHED_MC */

#if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
@@ -7815,8 +7817,8 @@ cpu_to_core_group(int cpu, const struct cpumask *cpu_map,
}
#endif

-static DEFINE_PER_CPU(struct static_sched_domain, phys_domains);
-static DEFINE_PER_CPU(struct static_sched_group, sched_group_phys);
+static DEFINE_PER_CPU(union static_sched_domain, phys_domains);
+static DEFINE_PER_CPU(union static_sched_group, sched_group_phys);

static int
cpu_to_phys_group(int cpu, const struct cpumask *cpu_map,
@@ -7843,11 +7845,11 @@ cpu_to_phys_group(int cpu, const struct cpumask *cpu_map,
* groups, so roll our own. Now each node has its own list of groups which
* gets dynamically allocated.
*/
-static DEFINE_PER_CPU(struct static_sched_domain, node_domains);
+static DEFINE_PER_CPU(union static_sched_domain, node_domains);
static struct sched_group ***sched_group_nodes_bycpu;

-static DEFINE_PER_CPU(struct static_sched_domain, allnodes_domains);
-static DEFINE_PER_CPU(struct static_sched_group, sched_group_allnodes);
+static DEFINE_PER_CPU(union static_sched_domain, allnodes_domains);
+static DEFINE_PER_CPU(union static_sched_group, sched_group_allnodes);

static int cpu_to_allnodes_group(int cpu, const struct cpumask *cpu_map,
struct sched_group **sg,

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