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Commit 84393817 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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: default avatarLarry Finger <Larry.Finger@lwfinger.net>
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarThomas 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>
parent b45e4c45

arch/x86/kernel/cpu/mtrr/main.c

+15 −3
Original line number Diff line number Diff line
@@ -237,6 +237,18 @@ set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type typ 
	stop_machine(mtrr_rendezvous_handler, &data, cpu_online_mask);

}



static void set_mtrr_cpuslocked(unsigned int reg, unsigned long base,

				unsigned long size, mtrr_type type)

{

	struct set_mtrr_data data = { .smp_reg = reg,

				      .smp_base = base,

				      .smp_size = size,

				      .smp_type = type

				    };



	stop_machine_cpuslocked(mtrr_rendezvous_handler, &data, cpu_online_mask);

}



static void set_mtrr_from_inactive_cpu(unsigned int reg, unsigned long base,

				      unsigned long size, mtrr_type type)

{
@@ -370,7 +382,7 @@ int mtrr_add_page(unsigned long base, unsigned long size, 
	/* Search for an empty MTRR */

	i = mtrr_if->get_free_region(base, size, replace);

	if (i >= 0) {

		set_mtrr(i, base, size, type);

		set_mtrr_cpuslocked(i, base, size, type);

		if (likely(replace < 0)) {

			mtrr_usage_table[i] = 1;

		} else {
@@ -378,7 +390,7 @@ int mtrr_add_page(unsigned long base, unsigned long size, 
			if (increment)

				mtrr_usage_table[i]++;

			if (unlikely(replace != i)) {

				set_mtrr(replace, 0, 0, 0);

				set_mtrr_cpuslocked(replace, 0, 0, 0);

				mtrr_usage_table[replace] = 0;

			}

		}
@@ -506,7 +518,7 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size) 
		goto out;

	}

	if (--mtrr_usage_table[reg] < 1)

		set_mtrr(reg, 0, 0, 0);

		set_mtrr_cpuslocked(reg, 0, 0, 0);

	error = reg;

 out:

	mutex_unlock(&mtrr_mutex);