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>
* published by the Free Software Foundation.
*/
#include <linux/atomic.h>
* 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>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>
static DEFINE_SPINLOCK(boot_lock);
static DEFINE_SPINLOCK(boot_lock);
+static DECLARE_COMPLETION(cpu_running);
+
/*
* "thread" is assumed to be a valid Meta hardware thread ID.
*/
/*
* "thread" is assumed to be a valid Meta hardware thread ID.
*/
*/
ret = boot_secondary(thread, idle);
if (ret == 0) {
*/
ret = boot_secondary(thread, idle);
if (ret == 0) {
- unsigned long timeout;
-
/*
* CPU was successfully started, wait for it
* to come online or time out.
*/
/*
* 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;
if (!cpu_online(cpu))
ret = -EIO;
* OK, now it's safe to let the boot CPU continue
*/
set_cpu_online(cpu, true);
* OK, now it's safe to let the boot CPU continue
*/
set_cpu_online(cpu, true);
+ complete(&cpu_running);
/*
* Enable local interrupts.
/*
* Enable local interrupts.