Messages in this thread Patch in this message | | | From | Alex Shi <> | Subject | [PATCH 2/2] sched: fix a logical error in select_task_rq_fair | Date | Thu, 26 Jul 2012 13:27:26 +0800 |
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If find_idlest_cpu() return '-1', and sd->child is NULL. The function select_task_rq_fair will return -1. That is not the function's purpose.
The patch introduced a latest_cpu as temporay varible to store find_idlest_cpu() return value, and let new_cpu to store the latest workable cpu. If find_idlest_cpu() doesn't find idlest cpu, we still have a latest workable cpu.
Signed-off-by: Alex Shi <alex.shi@intel.com> --- kernel/sched/fair.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 8a1db69..7e4bab48 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2730,6 +2730,7 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) int load_idx = sd->forkexec_idx; struct sched_group *group; int weight; + int latest_cpu; if (!(sd->flags & sd_flag)) { sd = sd->child; @@ -2745,8 +2746,12 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) continue; } - new_cpu = find_idlest_cpu(group, p, cpu); - if (new_cpu == -1 || new_cpu == cpu) { + latest_cpu = find_idlest_cpu(group, p, cpu); + + if (latest_cpu != -1) + new_cpu = latest_cpu; + + if (latest_cpu == -1 || latest_cpu == cpu) { /* Now try balancing at a lower domain level of cpu */ sd = sd->child; continue; -- 1.7.5.4
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