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authorJames Hogan <james.hogan@imgtec.com>2013-06-28 15:03:05 +0100
committerJames Hogan <james.hogan@imgtec.com>2013-07-02 11:03:52 +0100
commit9649814432faa9016952895684120942da0d8481 (patch)
tree3a4c5862e7dd092a030f7276ebb34c34d68090ce /arch/metag
parent234c7f1ac109ad1af4ae410463d03ccebf3d6657 (diff)
downloadlinux-linaro-stable-9649814432faa9016952895684120942da0d8481.tar.gz
metag: smp: don't spin waiting for CPU to start
Use a completion to block until a secondary CPU has started up, like ARM do, instead of a loop of udelays. On Meta, SMP is really SMT, with each "CPU" being a different hardware thread on the same Meta processor core, so as well as being more efficient and latency friendly, using a completion prevents the bogomips of the secondary CPU from being drastically skewed every time by the execution of the tight in-cache udelay loop on the other CPU. Signed-off-by: James Hogan <james.hogan@imgtec.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Diffstat (limited to 'arch/metag')
-rw-r--r--arch/metag/kernel/smp.c16
1 files changed, 6 insertions, 10 deletions
diff --git a/arch/metag/kernel/smp.c b/arch/metag/kernel/smp.c
index 09979f203a4d..e413875cf6d2 100644
--- a/arch/metag/kernel/smp.c
+++ b/arch/metag/kernel/smp.c
@@ -8,6 +8,7 @@
* published by the Free Software Foundation.
*/
#include <linux/atomic.h>
+#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>
@@ -62,6 +63,8 @@ static DEFINE_PER_CPU(struct ipi_data, ipi_data) = {
static DEFINE_SPINLOCK(boot_lock);
+static DECLARE_COMPLETION(cpu_running);
+
/*
* "thread" is assumed to be a valid Meta hardware thread ID.
*/
@@ -235,20 +238,12 @@ int __cpuinit __cpu_up(unsigned int cpu, struct task_struct *idle)
*/
ret = boot_secondary(thread, idle);
if (ret == 0) {
- unsigned long timeout;
-
/*
* CPU was successfully started, wait for it
* to come online or time out.
*/
- timeout = jiffies + HZ;
- while (time_before(jiffies, timeout)) {
- if (cpu_online(cpu))
- break;
-
- udelay(10);
- barrier();
- }
+ wait_for_completion_timeout(&cpu_running,
+ msecs_to_jiffies(1000));
if (!cpu_online(cpu))
ret = -EIO;
@@ -391,6 +386,7 @@ asmlinkage void secondary_start_kernel(void)
* OK, now it's safe to let the boot CPU continue
*/
set_cpu_online(cpu, true);
+ complete(&cpu_running);
/*
* Enable local interrupts.