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Subject[PATCH v4 08/12] sched/topology: Check SDF_SHARED_CHILD in highest_flag_domain()
Date
Do not assume that all the children of a scheduling domain have a given
flag. Check whether it has the SDF_SHARED_CHILD meta flag.

Cc: Ben Segall <bsegall@google.com>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tim C. Chen <tim.c.chen@intel.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v3:
* Introduced this patch.

Changes since v2:
* N/A

Changes since v1:
* N/A
---
kernel/sched/sched.h | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 060616944d7a..70abce91b549 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1772,6 +1772,13 @@ queue_balance_callback(struct rq *rq,
for (__sd = rcu_dereference_check_sched_domain(cpu_rq(cpu)->sd); \
__sd; __sd = __sd->parent)

+/* A mask of all the SD flags that have the SDF_SHARED_CHILD metaflag */
+#define SD_FLAG(name, mflags) (name * !!((mflags) & SDF_SHARED_CHILD)) |
+static const unsigned int SD_SHARED_CHILD_MASK =
+#include <linux/sched/sd_flags.h>
+0;
+#undef SD_FLAG
+
/**
* highest_flag_domain - Return highest sched_domain containing flag.
* @cpu: The CPU whose highest level of sched domain is to
@@ -1779,16 +1786,25 @@ queue_balance_callback(struct rq *rq,
* @flag: The flag to check for the highest sched_domain
* for the given CPU.
*
- * Returns the highest sched_domain of a CPU which contains the given flag.
+ * Returns the highest sched_domain of a CPU which contains @flag. If @flag has
+ * the SDF_SHARED_CHILD metaflag, all the children domains also have @flag.
*/
static inline struct sched_domain *highest_flag_domain(int cpu, int flag)
{
struct sched_domain *sd, *hsd = NULL;

for_each_domain(cpu, sd) {
- if (!(sd->flags & flag))
+ if (sd->flags & flag) {
+ hsd = sd;
+ continue;
+ }
+
+ /*
+ * Stop the search if @flag is known to be shared at lower
+ * levels. It will not be found further up.
+ */
+ if (flag & SD_SHARED_CHILD_MASK)
break;
- hsd = sd;
}

return hsd;
--
2.25.1
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