Linux Kernel Architecture
Chapter 15: Time Management The kernel distinguishes between two types of clocks: Aglobal clockis responsible to provide the pe ...
Chapter 15: Time Management provide both are considered.^9 Actually most widespread architectures have been updated to support b ...
Chapter 15: Time Management Note that a direct interpretation of aktime_tas a number of nanoseconds would be possible on 64-bit ...
Chapter 15: Time Management ❑ Clocks with a rating between 300 and 399 are reasonably fast and accurate. ❑ Perfect clocks that a ...
Chapter 15: Time Management At a first glance, it might not make much sense to first multiply byJIFFIES_SHIFTand then again divi ...
Chapter 15: Time Management Clock Event Devices Clock event devices are defined by the following data structure: <clockchips. ...
Chapter 15: Time Management ❑ irqspecifies the number of the IRQ that is used by the event device. Note that this is only requir ...
Chapter 15: Time Management to handle global clock events on x86 systems, the global variableglobal_clock_eventas defined in arc ...
Chapter 15: Time Management To set up a tick device, the kernel provides the functiontick_setup_device. The prototype is as foll ...
Chapter 15: Time Management Before discussing these functions, let us therefore consider which situations are faced by the kerne ...
Chapter 15: Time Management Actually, the task is quite simple if the clock event device supports periodic events. In this case, ...
Chapter 15: Time Management All the kernel needs to do is calltick_periodic. If the clock event device operates in one-shot mode ...
Chapter 15: Time Management Components of the high-resolution timer framework that are not universally applicable, but do really ...
Chapter 15: Time Management ktime_t (*get_softirq_time)(void); ktime_t softirq_time; #ifdef CONFIG_HIGH_RES_TIMERS ktime_t offse ...
Chapter 15: Time Management ❑ expires_nextcontains the absolute time of the next event that is due for expiration. ❑ hres_active ...
Chapter 15: Time Management nodeis used to keep the timer on the red-black tree as mentioned above, andbasepoints to the timer b ...
Chapter 15: Time Management The expiration of the timer must be set to a future point in time. The callback function can perfor ...
Chapter 15: Time Management The implementation of both functions is purely technical and not very interesting, their code need n ...
Chapter 15: Time Management struct hrtimer_clock_base *base; ktime_t expires_next, now; ... retry: now = ktime_get(); expires_ne ...
Chapter 15: Time Management if (expires.tv64 < expires_next.tv64) expires_next = expires; break; } If the next timer’s expira ...
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