From: Peter Zijlstra <pet...@infradead.org>
Memory for tvec_base is allocated separately for boot CPU (statically) and
non-boot CPUs (dynamically).
The reason is because __TIMER_INITIALIZER() needs to set ->base to a valid
pointer (because we've made NULL special, hint: lock_timer_base()) and we cannot
get a compile time pointer to per-cpu entries because we don't know where we'll
map the section, even for the boot cpu.
This can be simplified a bit by statically allocating per-cpu memory. The only
disadvantage is that memory for one of the structures will stay unused, i.e. for
the boot CPU, which uses boot_tvec_bases.
This will also guarantee that tvec_base is cacheline aligned. Even though
tvec_base has ____cacheline_aligned stuck on, kzalloc_node() does not actually
respect that (but guarantees a minimum u64 alignment).
Signed-off-by: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Viresh Kumar <viresh.ku...@linaro.org>
---
kernel/time/timer.c | 36 ++++++++----------------------------
1 file changed, 8 insertions(+), 28 deletions(-)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 2d3f5c504939..6e8220ec8a62 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -93,6 +93,7 @@ struct tvec_base {
struct tvec_base boot_tvec_bases;
EXPORT_SYMBOL(boot_tvec_bases);
static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;
+static DEFINE_PER_CPU(struct tvec_base, __tvec_bases);
/* Functions below help us manage 'deferrable' flag */
static inline unsigned int tbase_get_deferrable(struct tvec_base *base)
@@ -1534,46 +1535,25 @@ EXPORT_SYMBOL(schedule_timeout_uninterruptible);
static int init_timers_cpu(int cpu)
{
- int j;
- struct tvec_base *base;
+ struct tvec_base *base = per_cpu(tvec_bases, cpu);
static char tvec_base_done[NR_CPUS];
+ int j;
if (!tvec_base_done[cpu]) {
static char boot_done;
- if (boot_done) {
- /*
- * The APs use this path later in boot
- */
- base = kzalloc_node(sizeof(*base), GFP_KERNEL,
- cpu_to_node(cpu));
- if (!base)
- return -ENOMEM;
-
- /* Make sure tvec_base has TIMER_FLAG_MASK bits free */
- if (WARN_ON(base != tbase_get_base(base))) {
- kfree(base);
- return -ENOMEM;
- }
- per_cpu(tvec_bases, cpu) = base;
+ if (!boot_done) {
+ boot_done = 1; /* skip the boot cpu */
} else {
- /*
- * 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;
+ base = per_cpu_ptr(&__tvec_bases, cpu);
+ per_cpu(tvec_bases, cpu) = base;
}
+
spin_lock_init(&base->lock);
tvec_base_done[cpu] = 1;
base->cpu = cpu;
- } else {
- base = per_cpu(tvec_bases, cpu);
}
-
for (j = 0; j < TVN_SIZE; j++) {
INIT_LIST_HEAD(base->tv5.vec + j);
INIT_LIST_HEAD(base->tv4.vec + j);
--
2.3.0.rc0.44.ga94655d
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