From: Mike Galbraith Date: Tue, 24 Mar 2015 08:14:49 +0100 Subject: hotplug: Use set_cpus_allowed_ptr() in sync_unplug_thread() Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.4/patches-4.4.1-rt6.tar.xz do_set_cpus_allowed() is not safe vs ->sched_class change. crash> bt PID: 11676 TASK: ffff88026f979da0 CPU: 22 COMMAND: "sync_unplug/22" #0 [ffff880274d25bc8] machine_kexec at ffffffff8103b41c #1 [ffff880274d25c18] crash_kexec at ffffffff810d881a #2 [ffff880274d25cd8] oops_end at ffffffff81525818 #3 [ffff880274d25cf8] do_invalid_op at ffffffff81003096 #4 [ffff880274d25d90] invalid_op at ffffffff8152d3de [exception RIP: set_cpus_allowed_rt+18] RIP: ffffffff8109e012 RSP: ffff880274d25e48 RFLAGS: 00010202 RAX: ffffffff8109e000 RBX: ffff88026f979da0 RCX: ffff8802770cb6e8 RDX: 0000000000000000 RSI: ffffffff81add700 RDI: ffff88026f979da0 RBP: ffff880274d25e78 R8: ffffffff816112e0 R9: 0000000000000001 R10: 0000000000000001 R11: 0000000000011940 R12: ffff88026f979da0 R13: ffff8802770cb6d0 R14: ffff880274d25fd8 R15: 0000000000000000 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 #5 [ffff880274d25e60] do_set_cpus_allowed at ffffffff8108e65f #6 [ffff880274d25e80] sync_unplug_thread at ffffffff81058c08 #7 [ffff880274d25ed8] kthread at ffffffff8107cad6 #8 [ffff880274d25f50] ret_from_fork at ffffffff8152bbbc crash> task_struct ffff88026f979da0 | grep class sched_class = 0xffffffff816111e0 , Signed-off-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior --- kernel/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -268,7 +268,7 @@ static int sync_unplug_thread(void *data * we don't want any more work on this CPU. */ current->flags &= ~PF_NO_SETAFFINITY; - do_set_cpus_allowed(current, cpu_present_mask); + set_cpus_allowed_ptr(current, cpu_present_mask); migrate_me(); return 0; }