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Subject[PATCH 4/7] x86/mce/amd: Sanitize thresholding device creation hotplug path
Date
From: Thomas Gleixner <tglx@linutronix.de>

Drop the stupid threshold_init_device() initcall iterating over all
online CPUs in favor of properly setting up everything on the CPU
hotplug path, when each CPU's callback is invoked.

[ bp: Write commit message. ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/cpu/mce/amd.c | 57 ++++++++++------------------------
arch/x86/kernel/cpu/mce/core.c | 11 +++++++
2 files changed, 27 insertions(+), 41 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index 563942157758..d3c416b6052a 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -1474,12 +1474,22 @@ int mce_threshold_remove_device(unsigned int cpu)
return 0;
}

-/* create dir/files for all valid threshold banks */
+/**
+ * mce_threshold_create_device - Create the per-CPU MCE threshold device
+ * @cpu: The plugged in CPU
+ *
+ * Create directories and files for all valid threshold banks.
+ *
+ * This is invoked from the CPU hotplug callback which was installed in
+ * mcheck_init_device(). The invocation happens in context of the hotplug
+ * thread running on @cpu. The callback is invoked on all CPUs which are
+ * online when the callback is installed or during a real hotplug event.
+ */
int mce_threshold_create_device(unsigned int cpu)
{
unsigned int bank;
struct threshold_bank **bp;
- int err = 0;
+ int err;

if (!mce_flags.amd_threshold)
return 0;
@@ -1500,49 +1510,14 @@ int mce_threshold_create_device(unsigned int cpu)
continue;
err = threshold_create_bank(cpu, bank);
if (err)
- goto err;
- }
- return err;
-err:
- mce_threshold_remove_device(cpu);
- return err;
-}
-
-static __init int threshold_init_device(void)
-{
- unsigned lcpu = 0;
-
- /* to hit CPUs online before the notifier is up */
- for_each_online_cpu(lcpu) {
- int err = mce_threshold_create_device(lcpu);
-
- if (err)
- return err;
+ goto out_err;
}

if (thresholding_irq_en)
mce_threshold_vector = amd_threshold_interrupt;

return 0;
+out_err:
+ mce_threshold_remove_device(cpu);
+ return err;
}
-/*
- * there are 3 funcs which need to be _initcalled in a logic sequence:
- * 1. xen_late_init_mcelog
- * 2. mcheck_init_device
- * 3. threshold_init_device
- *
- * xen_late_init_mcelog must register xen_mce_chrdev_device before
- * native mce_chrdev_device registration if running under xen platform;
- *
- * mcheck_init_device should be inited before threshold_init_device to
- * initialize mce_device, otherwise a NULL ptr dereference will cause panic.
- *
- * so we use following _initcalls
- * 1. device_initcall(xen_late_init_mcelog);
- * 2. device_initcall_sync(mcheck_init_device);
- * 3. late_initcall(threshold_init_device);
- *
- * when running under xen, the initcall order is 1,2,3;
- * on baremetal, we skip 1 and we do only 2 and 3.
- */
-late_initcall(threshold_init_device);
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 43ca91e14a77..a6009efdfe2b 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -2481,6 +2481,13 @@ static __init void mce_init_banks(void)
}
}

+/*
+ * When running on XEN, this initcall is ordered against the XEN mcelog
+ * initcall:
+ *
+ * device_initcall(xen_late_init_mcelog);
+ * device_initcall_sync(mcheck_init_device);
+ */
static __init int mcheck_init_device(void)
{
int err;
@@ -2512,6 +2519,10 @@ static __init int mcheck_init_device(void)
if (err)
goto err_out_mem;

+ /*
+ * Invokes mce_cpu_online() on all CPUs which are online when
+ * the state is installed.
+ */
err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/mce:online",
mce_cpu_online, mce_cpu_pre_down);
if (err < 0)
--
2.21.0
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