Revert "BACKPORT: FROMGIT: sched: Enforce user requested affinity"

This reverts commit ec8cf94166.

This series is responsible for a functional regression with task
affinity failing to take into account offline CPUs. Although this has
been reported upstream, work to fix the problem is ongoing and we're
better off reverting these changes from android13-5.15.

Link: https://lore.kernel.org/lkml/20230131221719.3176-1-will@kernel.org/
Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 263926519
Bug: 264940090
Change-Id: I3d6b07f62219773b0037f6ed347943e0fb6ef325

kernel/sched/core.c

@@ -2959,15 +2959,6 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
 	struct rq *rq;
 
 	rq = task_rq_lock(p, &rf);
-	/*
-	 * Masking should be skipped if SCA_USER or any of the SCA_MIGRATE_*
-	 * flags are set.
-	 */
-	if (p->user_cpus_ptr &&
-	    !(ctx->flags & (SCA_USER | SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) &&
-	    cpumask_and(rq->scratch_mask, ctx->new_mask, p->user_cpus_ptr))
-		ctx->new_mask = rq->scratch_mask;
-
 	return __set_cpus_allowed_ptr_locked(p, ctx, rq, &rf);
 }
 
@@ -9738,7 +9729,6 @@ void __init sched_init(void)
 
 		rq->core_cookie = 0UL;
 #endif
-		zalloc_cpumask_var_node(&rq->scratch_mask, GFP_KERNEL, cpu_to_node(i));
 	}
 
 	set_load_weight(&init_task, false);

kernel/sched/sched.h

@@ -1130,9 +1130,6 @@ struct rq {
 	unsigned int		core_forceidle_seq;
 #endif
 
-	/* Scratch cpumask to be temporarily used under rq_lock */
-	cpumask_var_t		scratch_mask;
-
 	ANDROID_VENDOR_DATA_ARRAY(1, 96);
 	ANDROID_OEM_DATA_ARRAY(1, 16);
 
@@ -1562,7 +1559,6 @@ struct rq_flags {
 	 */
 	unsigned int clock_update_flags;
 #endif
-
 };
 
 #ifdef CONFIG_SMP