[tip: sched/urgent] sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption

[tip-bot2 for Scott Wood]

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     16568f1f4fd4decee6935751d5ada1f963e5bd5f
Gitweb:        https://git.kernel.org/tip/16568f1f4fd4decee6935751d5ada1f963e5bd5f
Author:        Scott Wood <swood@xxxxxxxxxx>
AuthorDate:    Wed, 17 Jun 2020 14:17:42 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 23 Jun 2020 10:42:30 +02:00

sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption

This function is concerned with the long-term CPU mask, not the
transitory mask the task might have while migrate disabled.  Before
this patch, if a task was migrate-disabled at the time
__set_cpus_allowed_ptr() was called, and the new mask happened to be
equal to the CPU that the task was running on, then the mask update
would be lost.

Signed-off-by: Scott Wood <swood@xxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200617121742.cpxppyi7twxmpin7@xxxxxxxxxxxxx
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 8f36032..9eeac94 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1637,7 +1637,7 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
 		goto out;
 	}
 
-	if (cpumask_equal(p->cpus_ptr, new_mask))
+	if (cpumask_equal(&p->cpus_mask, new_mask))
 		goto out;
 
 	/*