Messages in this thread Patch in this message | | | Date | Fri, 7 May 2021 13:57:10 -0300 | From | Marcelo Tosatti <> | Subject | [PATCH] Revert "isolcpus: Affine unbound kernel threads to housekeeping cpus" |
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commit 9cc5b8656892a72438ee7deb introduced a new housekeeping flag, HK_FLAG_KTHREAD, that when enabled sets the CPU affinity for the kthreadd process (therefore all unbounded kernel threads created from that point on will use the housekeeping cpumask).
This is not necessary, since its possible to control placement of kthreadd from userspace:
# taskset -c -p 0 `pgrep kthreadd` pid 2's current affinity list: 1 pid 2's new affinity list: 0
Unbounded kernel threads started from that point on will inherit the kthreadd cpumask.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Index: linux-2.6/include/linux/sched/isolation.h =================================================================== --- linux-2.6.orig/include/linux/sched/isolation.h +++ linux-2.6/include/linux/sched/isolation.h @@ -14,7 +14,6 @@ enum hk_flags { HK_FLAG_DOMAIN = (1 << 5), HK_FLAG_WQ = (1 << 6), HK_FLAG_MANAGED_IRQ = (1 << 7), - HK_FLAG_KTHREAD = (1 << 8), }; #ifdef CONFIG_CPU_ISOLATION Index: linux-2.6/kernel/kthread.c =================================================================== --- linux-2.6.orig/kernel/kthread.c +++ linux-2.6/kernel/kthread.c @@ -27,7 +27,6 @@ #include <linux/ptrace.h> #include <linux/uaccess.h> #include <linux/numa.h> -#include <linux/sched/isolation.h> #include <trace/events/sched.h> @@ -405,8 +404,7 @@ struct task_struct *__kthread_create_on_ * The kernel thread should not inherit these properties. */ sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m); - set_cpus_allowed_ptr(task, - housekeeping_cpumask(HK_FLAG_KTHREAD)); + set_cpus_allowed_ptr(task, cpu_possible_mask); } kfree(create); return task; @@ -655,7 +653,7 @@ int kthreadd(void *unused) /* Setup a clean context for our children to inherit. */ set_task_comm(tsk, "kthreadd"); ignore_signals(tsk); - set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_FLAG_KTHREAD)); + set_cpus_allowed_ptr(tsk, cpu_possible_mask); set_mems_allowed(node_states[N_MEMORY]); current->flags |= PF_NOFREEZE; Index: linux-2.6/kernel/sched/isolation.c =================================================================== --- linux-2.6.orig/kernel/sched/isolation.c +++ linux-2.6/kernel/sched/isolation.c @@ -140,8 +140,7 @@ static int __init housekeeping_nohz_full { unsigned int flags; - flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU | - HK_FLAG_MISC | HK_FLAG_KTHREAD; + flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC; return housekeeping_setup(str, flags); }
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