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Subject[PATCH RT 4/5] hotplug: Use set_cpus_allowed_ptr() in sync_unplug_thread()
3.14.39-rt38-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Mike Galbraith <umgwanakikbuti@gmail.com>

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 <fair_sched_class+64>,

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/cpu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 285e18b2c420..a3890754e407 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -242,7 +242,7 @@ 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;
}
--
2.1.4



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