Thanks for the quick reply.
On Wed, Mar 28, 2018 at 6:19 AM, Richard Weinberger <rich...@nod.at> wrote:
> Am Mittwoch, 28. März 2018, 15:11:29 CEST schrieb Geert Uytterhoeven:
>> On Wed, Mar 28, 2018 at 12:28 PM, Joel Fernandes <agnel.j...@gmail.com>
> wrote:
>> > while(release_now == 0);
>>
>> while (release_now == 0)
>> cpu_relax();
>
> Not sure whether a cpu_relax() fixes the problem.
> I guess the root of the problem is that UML is UP and non-preemptive.
> Therefore the loop is never interrupted.
> To verify I asked for the full source.
>
cpu_relax actually worked!
Any thoughts on why it helps? Even if its non-preemptive, I did
receive the timer interrupt, so I expected the variable to be set.
Module is attached.
Thanks,
-Joel
/*
* This module emits "Hello, world" on printk when loaded.
*
* It is designed to be used for basic evaluation of the module loading
* subsystem (for example when validating module signing/verification). It
* lacks any extra dependencies, and will not normally be loaded by the
* system unless explicitly requested by name.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/init.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/ratelimit.h>
#include <linux/delay.h>
#include <linux/sched.h>
struct bigstr {
spinlock_t biglock;
};
struct bigstr *il;
struct hrtimer bigtimer;
int release_now;
static enum hrtimer_restart bigtimer_handle(struct hrtimer *timer)
{
printk(KERN_ERR "timer fired 2\n");
spin_lock(&il->biglock);
spin_unlock(&il->biglock);
release_now = 1;
return HRTIMER_NORESTART;
}
void init_bigstr(struct bigstr *b)
{
spin_lock_init(&b->biglock);
}
static int __init test_module_init(void)
{
struct bigstr b1, b2;
struct hrtimer *timer;
release_now = 0;
init_bigstr(&b1);
init_bigstr(&b2);
timer = &bigtimer;
timer->debug = 1;
hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
timer->function = bigtimer_handle;
il = &b2;
spin_lock(&b1.biglock);
printk(KERN_ERR "Starting timer\n");
hrtimer_start(timer, ns_to_ktime(50000ULL),
HRTIMER_MODE_REL_PINNED);
while(release_now == 0)
cpu_relax();
spin_unlock(&b1.biglock);
return -1;
}
module_init(test_module_init);
static void __exit test_module_exit(void)
{
}
module_exit(test_module_exit);
MODULE_AUTHOR("Joel Fernandes <agnel.j...@gmail.com>");
MODULE_LICENSE("GPL");
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