init: rename and re-order boot_cpu_state_init()

commit b5b1404d0815894de0690de8a1ab58269e56eae6 upstream.

This is purely a preparatory patch for upcoming changes during the 4.19
merge window.

We have a function called "boot_cpu_state_init()" that isn't really
about the bootup cpu state: that is done much earlier by the similarly
named "boot_cpu_init()" (note lack of "state" in name).

This function initializes some hotplug CPU state, and needs to run after
the percpu data has been properly initialized.  It even has a comment to
that effect.

Except it _doesn't_ actually run after the percpu data has been properly
initialized.  On x86 it happens to do that, but on at least arm and
arm64, the percpu base pointers are initialized by the arch-specific
'smp_prepare_boot_cpu()' hook, which ran _after_ boot_cpu_state_init().

This had some unexpected results, and in particular we have a patch
pending for the merge window that did the obvious cleanup of using
'this_cpu_write()' in the cpu hotplug init code:

  -       per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
  +       this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);

which is obviously the right thing to do.  Except because of the
ordering issue, it actually failed miserably and unexpectedly on arm64.

So this just fixes the ordering, and changes the name of the function to
be 'boot_cpu_hotplug_init()' to make it obvious that it's about cpu
hotplug state, because the core CPU state was supposed to have already
been done earlier.

Marked for stable, since the (not yet merged) patch that will show this
problem is marked for stable.

Reported-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 917829b27350f7036c66eec0e9388045b605d890..f1da93d0c34fa6c52acf60f81b47b73c9f2689e0 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -29,7 +29,7 @@ struct cpu {
 };
 
 extern void boot_cpu_init(void);
-extern void boot_cpu_state_init(void);
+extern void boot_cpu_hotplug_init(void);
 
 extern int register_cpu(struct cpu *cpu, int num);
 extern struct device *get_cpu_device(unsigned cpu);

diff --git a/init/main.c b/init/main.c
index f22957afb37e0e6e4b0b0cfa3c3fade080de674c..4313772d634acab70a53c9c499612f8047697dd6 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -509,8 +509,8 @@ asmlinkage __visible void __init start_kernel(void)
        setup_command_line(command_line);
        setup_nr_cpu_ids();
        setup_per_cpu_areas();
-       boot_cpu_state_init();
        smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
+       boot_cpu_hotplug_init();
 
        build_all_zonelists(NULL, NULL);
        page_alloc_init();

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 967163fb90a835b3481444fc7937aa6e32b9d79b..e93635e2376f76d8a42b9cca20af4b9ad184ad07 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1944,7 +1944,7 @@ void __init boot_cpu_init(void)
 /*
  * Must be called _AFTER_ setting up the per_cpu areas
  */
-void __init boot_cpu_state_init(void)
+void __init boot_cpu_hotplug_init(void)
 {
        per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
 }