[PATCH] timer initialisation fix

We need the boot CPU's tvec_bases[] entry to be initialised super-early in
boot, for early_serial_setup().  That runs within setup_arch(), before even
per-cpu areas are initialised.

The patch changes tvec_bases to use compile-time initialisation, and adds a
separate array `tvec_base_done' to keep track of which CPU has had its
tvec_bases[] entry initialised (because we can no longer use the zeroness of
that tvec_bases[] entry to determine whether it has been initialised).

Thanks to Eugene Surovegin <ebs@ebshome.net> for diagnosing this.

Cc: Eugene Surovegin <ebs@ebshome.net>
Cc: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/timer.c b/kernel/timer.c
index 471ab87..8837737 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -81,9 +81,10 @@ struct tvec_t_base_s {
 } ____cacheline_aligned_in_smp;
 
 typedef struct tvec_t_base_s tvec_base_t;
-static DEFINE_PER_CPU(tvec_base_t *, tvec_bases);
+
 tvec_base_t boot_tvec_bases;
 EXPORT_SYMBOL(boot_tvec_bases);
+static DEFINE_PER_CPU(tvec_base_t *, tvec_bases) = { &boot_tvec_bases };
 
 static inline void set_running_timer(tvec_base_t *base,
                                        struct timer_list *timer)
@@ -1224,28 +1225,36 @@ static int __devinit init_timers_cpu(int cpu)
 {
        int j;
        tvec_base_t *base;
+       static char __devinitdata tvec_base_done[NR_CPUS];
 
-       base = per_cpu(tvec_bases, cpu);
-       if (!base) {
+       if (!tvec_base_done[cpu]) {
                static char boot_done;
 
-               /*
-                * Cannot do allocation in init_timers as that runs before the
-                * allocator initializes (and would waste memory if there are
-                * more possible CPUs than will ever be installed/brought up).
-                */
                if (boot_done) {
+                       /*
+                        * The APs use this path later in boot
+                        */
                        base = kmalloc_node(sizeof(*base), GFP_KERNEL,
                                                cpu_to_node(cpu));
                        if (!base)
                                return -ENOMEM;
                        memset(base, 0, sizeof(*base));
+                       per_cpu(tvec_bases, cpu) = base;
                } else {
-                       base = &boot_tvec_bases;
+                       /*
+                        * This is for the boot CPU - we use compile-time
+                        * static initialisation because per-cpu memory isn't
+                        * ready yet and because the memory allocators are not
+                        * initialised either.
+                        */
                        boot_done = 1;
+                       base = &boot_tvec_bases;
                }
-               per_cpu(tvec_bases, cpu) = base;
+               tvec_base_done[cpu] = 1;
+       } else {
+               base = per_cpu(tvec_bases, cpu);
        }
+
        spin_lock_init(&base->lock);
        for (j = 0; j < TVN_SIZE; j++) {
                INIT_LIST_HEAD(base->tv5.vec + j);