static int sys_vperfctr_iresume(struct vperfctr *perfctr, const struct task_struct *tsk)
{
#ifdef CONFIG_PERFCTR_INTERRUPT_SUPPORT
unsigned int iresume_cstatus;
if (!tsk)
return -ESRCH; /* attempt to update unlinked perfctr */
iresume_cstatus = perfctr->iresume_cstatus;
if (!perfctr_cstatus_has_ictrs(iresume_cstatus))
return -EPERM;
/* PREEMPT note: preemption is disabled over the entire
region because we're updating an active perfctr. */
preempt_disable();
if (IS_RUNNING(perfctr) && tsk == current)
vperfctr_suspend(perfctr);
perfctr->cpu_state.cstatus = iresume_cstatus;
perfctr->iresume_cstatus = 0;
/* remote access note: perfctr_cpu_ireload() is ok */
perfctr_cpu_ireload(&perfctr->cpu_state);
if (tsk == current)
vperfctr_resume(perfctr);
preempt_enable();
return 0;
#else
return -ENOSYS;
#endif
}
static inline void vperfctr_ireload(struct vperfctr *perfctr)
{
#ifdef CONFIG_PERFCTR_INTERRUPT_SUPPORT
if (perfctr->ireload_needed) {
perfctr->ireload_needed = 0;
/* remote access note: perfctr_cpu_ireload() is ok */
perfctr_cpu_ireload(&perfctr->cpu_state);
}
#endif
}
static int do_vperfctr_iresume(struct vperfctr *perfctr, const struct task_struct *tsk)
{
#ifdef CONFIG_PERFCTR_INTERRUPT_SUPPORT
unsigned int iresume_cstatus;
if (!tsk)
return -ESRCH; /* attempt to update unlinked perfctr */
iresume_cstatus = perfctr->iresume_cstatus;
if (!perfctr_cstatus_has_ictrs(iresume_cstatus)) {
return -EPERM;
}
/* PREEMPT note: preemption is disabled over the entire
region because we're updating an active perfctr. */
preempt_disable();
// this is for resuming a task whose signal was handled prior to this call
// are the i-mode counters frozen before the overflow-signal is delivered
// yes, they are. in the suspend call invoked in the handler
// why exactly are we suspending the following? Makes sense ... if the
// counters are already running, then one should not just resume the task
// which will overwrite the PMC registers with old values. Nice. Under
// what condition do counters continue to count after the signal is delivered
// remember TSC was not suspend in the handler and continues to count
if (IS_RUNNING(perfctr) && tsk == current)
vperfctr_suspend(perfctr);
// setting the cstatus of 'cpu_state' back to what it was prior to its
// zeroing out in the interrupt handler
perfctr->cpu_state.cstatus = iresume_cstatus;
perfctr->iresume_cstatus = 0;
/* remote access note: perfctr_cpu_ireload() is ok */
// the following forces the reload of control registers that
// unfreezes the i-mode registers
perfctr_cpu_ireload(&perfctr->cpu_state);
if (tsk == current)
vperfctr_resume(perfctr);
preempt_enable();
return 0;
#else
return -ENOSYS;
#endif
}
