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 9546bf2fe31058ba57b7f95e0a990784aff4506b..dc491b3cf4a63997fd9f79968219cc314cc75679 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -30,7 +30,7 @@ struct cpu {
 };
 
 extern void boot_cpu_init(void);
-extern void boot_cpu_state_init(void);
+extern void boot_cpu_hotplug_init(void);
 extern void cpu_init(void);
 extern void trap_init(void);
 

diff --git a/init/main.c b/init/main.c
index 0d88f37febcb29d56a1f18297a9b9a63dddb5243..c4a45145e102db935d2b7c6032b24e2e797189a1 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -543,8 +543,8 @@ 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);
        page_alloc_init();

diff --git a/kernel/cpu.c b/kernel/cpu.c
index f21bfa3172d8a0c460142ed3ba1c6095f0fdcb48..d6affe6bd6b62afb62c1b914cdf8285187d1059e 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2022,7 +2022,7 @@ 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;
 }