x86/mtrr: Prevent CPU hotplug lock recursion
authorThomas Gleixner <tglx@linutronix.de>
Tue, 15 Aug 2017 11:03:47 +0000 (13:03 +0200)
committerThomas Gleixner <tglx@linutronix.de>
Tue, 15 Aug 2017 11:03:47 +0000 (13:03 +0200)
commit84393817db09bb436e934f8f8cc981cbca9ea4dc
tree90759da335f746a81f1019271bfb75370dc38314
parentb45e4c45b13275a6b4a3f83ae8301a1963fbe5d0
x86/mtrr: Prevent CPU hotplug lock recursion

Larry reported a CPU hotplug lock recursion in the MTRR code.

============================================
WARNING: possible recursive locking detected

systemd-udevd/153 is trying to acquire lock:
 (cpu_hotplug_lock.rw_sem){.+.+.+}, at: [<c030fc26>] stop_machine+0x16/0x30

 but task is already holding lock:
  (cpu_hotplug_lock.rw_sem){.+.+.+}, at: [<c0234353>] mtrr_add_page+0x83/0x470

....

 cpus_read_lock+0x48/0x90
 stop_machine+0x16/0x30
 mtrr_add_page+0x18b/0x470
 mtrr_add+0x3e/0x70

mtrr_add_page() holds the hotplug rwsem already and calls stop_machine()
which acquires it again.

Call stop_machine_cpuslocked() instead.

Reported-and-tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1708140920250.1865@nanos
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Borislav Petkov <bp@suse.de>
arch/x86/kernel/cpu/mtrr/main.c