aboutsummaryrefslogtreecommitdiff
path: root/kernel/sched/fair.c
diff options
context:
space:
mode:
authorLukasz Luba2020-08-10 09:30:04 +0100
committerPeter Zijlstra2020-08-26 12:41:57 +0200
commitda0777d35f47892f359c3f73ea155870bb595700 (patch)
treef8331fb265b93c0addddf8ece95d0b8b12fd523f /kernel/sched/fair.c
parentec73240b1627cddfd7cef018c7fa1c32e64a721e (diff)
sched/fair: Fix wrong negative conversion in find_energy_efficient_cpu()
In find_energy_efficient_cpu() 'cpu_cap' could be less that 'util'. It might be because of RT, DL (so higher sched class than CFS), irq or thermal pressure signal, which reduce the capacity value. In such situation the result of 'cpu_cap - util' might be negative but stored in the unsigned long. Then it might be compared with other unsigned long when uclamp_rq_util_with() reduced the 'util' such that is passes the fits_capacity() check. Prevent this situation and make the arithmetic more safe. Fixes: 1d42509e475cd ("sched/fair: Make EAS wakeup placement consider uclamp restrictions") Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20200810083004.26420-1-lukasz.luba@arm.com
Diffstat (limited to 'kernel/sched/fair.c')
-rw-r--r--kernel/sched/fair.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index abdb54e2339f..90ebaa4ae16e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6594,7 +6594,8 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
util = cpu_util_next(cpu, p, cpu);
cpu_cap = capacity_of(cpu);
- spare_cap = cpu_cap - util;
+ spare_cap = cpu_cap;
+ lsub_positive(&spare_cap, util);
/*
* Skip CPUs that cannot satisfy the capacity request.