#include <linux/kallsyms.h>
#include <linux/perf_event.h>
#include <linux/sched.h>
+#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
}
EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
+/**
+ * set_timer_slack - set the allowed slack for a timer
+ * @slack_hz: the amount of time (in jiffies) allowed for rounding
+ *
+ * Set the amount of time, in jiffies, that a certain timer has
+ * in terms of slack. By setting this value, the timer subsystem
+ * will schedule the actual timer somewhere between
+ * the time mod_timer() asks for, and that time plus the slack.
+ *
+ * By setting the slack to -1, a percentage of the delay is used
+ * instead.
+ */
+void set_timer_slack(struct timer_list *timer, int slack_hz)
+{
+ timer->slack = slack_hz;
+}
+EXPORT_SYMBOL_GPL(set_timer_slack);
+
static inline void set_running_timer(struct tvec_base *base,
struct timer_list *timer)
{
timer->entry.next = NULL;
timer->base = __raw_get_cpu_var(tvec_bases);
+ timer->slack = -1;
#ifdef CONFIG_TIMER_STATS
timer->start_site = NULL;
timer->start_pid = -1;
}
EXPORT_SYMBOL(mod_timer_pending);
+/*
+ * Decide where to put the timer while taking the slack into account
+ *
+ * Algorithm:
+ * 1) calculate the maximum (absolute) time
+ * 2) calculate the highest bit where the expires and new max are different
+ * 3) use this bit to make a mask
+ * 4) use the bitmask to round down the maximum time, so that all last
+ * bits are zeros
+ */
+static inline
+unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
+{
+ unsigned long expires_limit, mask;
+ int bit;
+
+ expires_limit = expires;
+
+ if (timer->slack >= 0) {
+ expires_limit = expires + timer->slack;
+ } else {
+ unsigned long now = jiffies;
+
+ /* No slack, if already expired else auto slack 0.4% */
+ if (time_after(expires, now))
+ expires_limit = expires + (expires - now)/256;
+ }
+ mask = expires ^ expires_limit;
+ if (mask == 0)
+ return expires;
+
+ bit = find_last_bit(&mask, BITS_PER_LONG);
+
+ mask = (1 << bit) - 1;
+
+ expires_limit = expires_limit & ~(mask);
+
+ return expires_limit;
+}
+
/**
* mod_timer - modify a timer's timeout
* @timer: the timer to be modified
if (timer_pending(timer) && timer->expires == expires)
return 1;
+ expires = apply_slack(timer, expires);
+
return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
}
EXPORT_SYMBOL(mod_timer);
if (base->running_timer == timer)
goto out;
+ timer_stats_timer_clear_start_info(timer);
ret = 0;
if (timer_pending(timer)) {
detach_timer(timer, 1);
lock_map_release(&lockdep_map);
if (preempt_count != preempt_count()) {
- printk(KERN_ERR "timer: %pF preempt leak: %08x -> %08x\n",
- fn, preempt_count, preempt_count());
- BUG();
+ WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
+ fn, preempt_count, preempt_count());
+ /*
+ * Restore the preempt count. That gives us a decent
+ * chance to survive and extract information. If the
+ * callback kept a lock held, bad luck, but not worse
+ * than the BUG() we had.
+ */
+ preempt_count() = preempt_count;
}
}
unsigned long action, void *hcpu)
{
long cpu = (long)hcpu;
+ int err;
+
switch(action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
- if (init_timers_cpu(cpu) < 0)
- return NOTIFY_BAD;
+ err = init_timers_cpu(cpu);
+ if (err < 0)
+ return notifier_from_errno(err);
break;
#ifdef CONFIG_HOTPLUG_CPU
case CPU_DEAD: