- Jan 16, 2018
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Anna-Maria Gleixner authored
hrtimer callbacks are always invoked in hard interrupt context. Several users in tree require soft interrupt context for their callbacks and achieve this by combining a hrtimer with a tasklet. The hrtimer schedules the tasklet in hard interrupt context and the tasklet callback gets invoked in softirq context later. That's suboptimal and aside of that the real-time patch moves most of the hrtimers into softirq context. So adding native support for hrtimers expiring in softirq context is a valuable extension for both mainline and the RT patch set. Each valid hrtimer clock id has two associated hrtimer clock bases: one for timers expiring in hardirq context and one for timers expiring in softirq context. Implement the functionality to associate a hrtimer with the hard or softirq related clock bases and update the relevant functions to take them into account when the next expiry time needs to be evaluated. Add a check into the hard interrupt context handler functions to check whether the first expiring softirq based timer has expired. If it's expired the softirq is raised and the accounting of softirq based timers to evaluate the next expiry time for programming the timer hardware is skipped until the softirq processing has finished. At the end of the softirq processing the regular processing is resumed. Suggested-by:
Thomas Gleixner <tglx@linutronix.de> Suggested-by:
Peter Zijlstra <peterz@infradead.org> Signed-off-by:
Anna-Maria Gleixner <anna-maria@linutronix.de> Cc: Christoph Hellwig <hch@lst.de> Cc: John Stultz <john.stultz@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: keescook@chromium.org Link: http://lkml.kernel.org/r/20171221104205.7269-29-anna-maria@linutronix.de Signed-off-by:
Ingo Molnar <mingo@kernel.org>
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- Jan 15, 2018
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Anna-Maria Gleixner authored
The softirq based hrtimer can utilize most of the existing hrtimers functions, but need to operate on a different data set. Add an 'active_mask' parameter to various functions so the hard and soft bases can be selected. Fixup the existing callers and hand in the ACTIVE_HARD mask. Signed-off-by:
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Anna-Maria Gleixner authored
Currently hrtimer callback functions are always executed in hard interrupt context. Users of hrtimers, which need their timer function to be executed in soft interrupt context, make use of tasklets to get the proper context. Add additional hrtimer clock bases for timers which must expire in softirq context, so the detour via the tasklet can be avoided. This is also required for RT, where the majority of hrtimer is moved into softirq hrtimer context. The selection of the expiry mode happens via a mode bit. Introduce HRTIMER_MODE_SOFT and the matching combinations with the ABS/REL/PINNED bits and update the decoding of hrtimer_mode in tracepoints. Signed-off-by:
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Anna-Maria Gleixner authored
__run_hrtimer() is called with the hrtimer_cpu_base.lock held and interrupts disabled. Before invoking the timer callback the base lock is dropped, but interrupts stay disabled. The upcoming support for softirq based hrtimers requires that interrupts are enabled before the timer callback is invoked. To avoid code duplication, take hrtimer_cpu_base.lock with raw_spin_lock_irqsave(flags) at the call site and hand in the flags as a parameter. So raw_spin_unlock_irqrestore() before the callback invocation will either keep interrupts disabled in interrupt context or restore to interrupt enabled state when called from softirq context. Suggested-by:
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Anna-Maria Gleixner authored
Preparatory patch for softirq based hrtimers to avoid code duplication. No functional change. Signed-off-by:
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Anna-Maria Gleixner authored
Preparatory patch for softirq based hrtimers to avoid code duplication, factor out the __hrtimer_start_range_ns() function from hrtimer_start_range_ns(). No functional change. Signed-off-by:
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Anna-Maria Gleixner authored
hrtimer_reprogram() must have access to the hrtimer_clock_base of the new first expiring timer to access hrtimer_clock_base.offset for adjusting the expiry time to CLOCK_MONOTONIC. This is required to evaluate whether the new left most timer in the hrtimer_clock_base is the first expiring timer of all clock bases in a hrtimer_cpu_base. The only user of hrtimer_reprogram() is hrtimer_start_range_ns(), which has a pointer to hrtimer_clock_base() already and hands it in as a parameter. But hrtimer_start_range_ns() will be split for the upcoming support for softirq based hrtimers to avoid code duplication and will lose the direct access to the clock base pointer. Instead of handing in timer and timer->base as a parameter remove the base parameter from hrtimer_reprogram() instead and retrieve the clock base internally. Signed-off-by:
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Anna-Maria Gleixner authored
The current decision whether a timer can be queued on a remote CPU checks for timer->expiry <= remote_cpu_base.expires_next. This is too restrictive because a timer with the same expiry time as an existing timer will be enqueued on right-hand size of the existing timer inside the rbtree, i.e. behind the first expiring timer. So its safe to allow enqueuing timers with the same expiry time as the first expiring timer on a remote CPU base. Signed-off-by:
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Anna-Maria Gleixner authored
hrtimer_reprogram() is conditionally invoked from hrtimer_start_range_ns() when hrtimer_cpu_base.hres_active is true. In the !hres_active case there is a special condition for the nohz_active case: If the newly enqueued timer expires before the first expiring timer on a remote CPU then the remote CPU needs to be notified and woken up from a NOHZ idle sleep to take the new first expiring timer into account. Previous changes have already established the prerequisites to make the remote enqueue behaviour the same whether high resolution mode is active or not: If the to be enqueued timer expires before the first expiring timer on a remote CPU, then it cannot be enqueued there. This was done for the high resolution mode because there is no way to access the remote CPU timer hardware. The same is true for NOHZ, but was handled differently by unconditionally enqueuing the timer and waking up the remote CPU so it can reprogram its timer. Again there is no compelling reason for this difference. hrtimer_check_target(), which makes the 'can remote enqueue' decision is already unconditional, but not yet functional because nothing updates hrtimer_cpu_base.expires_next in the !hres_active case. To unify this the following changes are required: 1) Make the store of the new first expiry time unconditonal in hrtimer_reprogram() and check __hrtimer_hres_active() before proceeding to the actual hardware access. This check also lets the compiler eliminate the rest of the function in case of CONFIG_HIGH_RES_TIMERS=n. 2) Invoke hrtimer_reprogram() unconditionally from hrtimer_start_range_ns() 3) Remove the remote wakeup special case for the !high_res && nohz_active case. Confine the timers_nohz_active static key to timer.c which is the only user now. Signed-off-by: -
Anna-Maria Gleixner authored
When the first hrtimer on the current CPU is removed, hrtimer_force_reprogram() is invoked but only when CONFIG_HIGH_RES_TIMERS=y and hrtimer_cpu_base.hres_active is set. hrtimer_force_reprogram() updates hrtimer_cpu_base.expires_next and reprograms the clock event device. When CONFIG_HIGH_RES_TIMERS=y and hrtimer_cpu_base.hres_active is set, a pointless hrtimer interrupt can be prevented. hrtimer_check_target() makes the 'can remote enqueue' decision. As soon as hrtimer_check_target() is unconditionally available and hrtimer_cpu_base.expires_next is updated by hrtimer_reprogram(), hrtimer_force_reprogram() needs to be available unconditionally as well to prevent the following scenario with CONFIG_HIGH_RES_TIMERS=n: - the first hrtimer on this CPU is removed and hrtimer_force_reprogram() is not executed - CPU goes idle (next timer is calculated and hrtimers are taken into account) - a hrtimer is enqueued remote on the idle CPU: hrtimer_check_target() compares expiry value and hrtimer_cpu_base.expires_next. The expiry value is after expires_next, so the hrtimer is enqueued. This timer will fire late, if it expires before the effective first hrtimer on this CPU and the comparison was with an outdated expires_next value. To prevent this scenario, make hrtimer_force_reprogram() unconditional except the effective reprogramming part, which gets eliminated by the compiler in the CONFIG_HIGH_RES_TIMERS=n case. Signed-off-by:
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Anna-Maria Gleixner authored
hrtimer_force_reprogram() needs to be available unconditionally for softirq based hrtimers. Move the function and all required struct members out of the CONFIG_HIGH_RES_TIMERS #ifdef. There is no functional change because hrtimer_force_reprogram() is only invoked when hrtimer_cpu_base.hres_active is true and CONFIG_HIGH_RES_TIMERS=y. Making it unconditional increases the text size for the CONFIG_HIGH_RES_TIMERS=n case slightly, but avoids replication of that code for the upcoming softirq based hrtimers support. Most of the code gets eliminated in the CONFIG_HIGH_RES_TIMERS=n case by the compiler. Signed-off-by:
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Anna-Maria Gleixner authored
hrtimer_reprogram() needs to be available unconditionally for softirq based hrtimers. Move the function and all required struct members out of the CONFIG_HIGH_RES_TIMERS #ifdef. There is no functional change because hrtimer_reprogram() is only invoked when hrtimer_cpu_base.hres_active is true. Making it unconditional increases the text size for the CONFIG_HIGH_RES_TIMERS=n case, but avoids replication of that code for the upcoming softirq based hrtimers support. Signed-off-by:
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Anna-Maria Gleixner authored
hrtimer_cpu_base.next_timer stores the pointer to the next expiring timer in a CPU base. This pointer cannot be dereferenced and is solely used to check whether a hrtimer which is removed is the hrtimer which is the first to expire in the CPU base. If this is the case, then the timer hardware needs to be reprogrammed to avoid an extra interrupt for nothing. Again, this is conditional functionality, but there is no compelling reason to make this conditional. As a preparation, hrtimer_cpu_base.next_timer needs to be available unconditonally. Aside of that the upcoming support for softirq based hrtimers requires access to this pointer unconditionally as well, so our motivation is not entirely simplicity based. Make the update of hrtimer_cpu_base.next_timer unconditional and remove the #ifdef cruft. The impact on CONFIG_HIGH_RES_TIMERS=n && CONFIG_NOHZ=n is marginal as it's just a store on an already dirtied cacheline. No functional change. Signed-off-by:
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Anna-Maria Gleixner authored
hrtimer_cpu_base.expires_next is used to cache the next event armed in the timer hardware. The value is used to check whether an hrtimer can be enqueued remotely. If the new hrtimer is expiring before expires_next, then remote enqueue is not possible as the remote hrtimer hardware cannot be accessed for reprogramming to an earlier expiry time. The remote enqueue check is currently conditional on CONFIG_HIGH_RES_TIMERS=y and hrtimer_cpu_base.hres_active. There is no compelling reason to make this conditional. Move hrtimer_cpu_base.expires_next out of the CONFIG_HIGH_RES_TIMERS=y guarded area and remove the conditionals in hrtimer_check_target(). The check is currently a NOOP for the CONFIG_HIGH_RES_TIMERS=n and the !hrtimer_cpu_base.hres_active case because in these cases nothing updates hrtimer_cpu_base.expires_next yet. This will be changed with later patches which further reduce the #ifdef zoo in this code. Signed-off-by:
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Anna-Maria Gleixner authored
__hrtimer_hres_active() is now available unconditionally, so replace open coded direct accesses to hrtimer_cpu_base.hres_active. No functional change. Signed-off-by:
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Anna-Maria Gleixner authored
The hrtimer_cpu_base::hres_active_member field depends on CONFIG_HIGH_RES_TIMERS=y currently, and all related functions to this member are conditional as well. To simplify the code make it unconditional and set it to zero during initialization. (This will also help with the upcoming softirq based hrtimers code.) The conditional code sections can be avoided by adding IS_ENABLED(HIGHRES) conditionals into common functions, which ensures dead code elimination. There is no functional change. Suggested-by:
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Anna-Maria Gleixner authored
The upcoming softirq based hrtimers support requires an additional field in the hrtimer_cpu_base struct, which would grow the struct size beyond a cache line. The hrtimer_cpu_base::nr_retries and ::nr_hangs members are solely used for diagnostic output and have no requirement to be 'unsigned int'. Make them 'unsigned short' to create room for the new struct member. No functional change. Signed-off-by:
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Anna-Maria Gleixner authored
The pointer to the currently running timer is stored in hrtimer_cpu_base before the base lock is dropped and the callback is invoked. This results in two levels of indirections and the upcoming support for softirq based hrtimer requires splitting the "running" storage into soft and hard IRQ context expiry. Storing both in the cpu base would require conditionals in all code paths accessing that information. It's possible to have a per clock base sequence count and running pointer without changing the semantics of the related mechanisms because the timer base pointer cannot be changed while a timer is running the callback. Unfortunately this makes cpu_clock base larger than 32 bytes on 32-bit kernels. Instead of having huge gaps due to alignment, remove the alignment and let the compiler pack CPU base for 32-bit kernels. The resulting cache access patterns are fortunately not really different from the current behaviour. On 64-bit kernels the 64-byte alignment stays and the behaviour is unchanged. This was determined by analyzing the resulting layout and looking at the number of cache lines involved for the frequently used clocks. Signed-off-by:
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Anna-Maria Gleixner authored
Looping over all clock bases to find active bits is suboptimal if not all bases are active. Avoid this by converting it to a __ffs() evaluation. The functionallity is outsourced into its own function and is called via a macro as suggested by Peter Zijlstra. Suggested-by:
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Anna-Maria Gleixner authored
The 'hrtimer_start' tracepoint lacks the mode information. The mode is important because consecutive starts can switch from ABS to REL or from PINNED to non PINNED. Append the mode field. Signed-off-by:
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Anna-Maria Gleixner authored
So far only CLOCK_MONOTONIC and CLOCK_REALTIME were taken into account as well as HRTIMER_MODE_ABS/REL in the hrtimer_init tracepoint. The query for detecting the ABS or REL timer modes is not valid anymore, it got broken by the introduction of HRTIMER_MODE_PINNED. HRTIMER_MODE_PINNED is not evaluated in the hrtimer_init() call, but for the sake of completeness print all given modes. Signed-off-by:
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Anna-Maria Gleixner authored
It's not obvious that the HRTIMER_MODE variants are bit combinations, because all modes are hard coded constants currently. Change it so the bit meanings are clear; and use the symbols for creating modes which combine bits. While at it get rid of the ugly tail comments as well. Signed-off-by:
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Anna-Maria Gleixner authored
The POSIX specification defines that relative CLOCK_REALTIME timers are not affected by clock modifications. Those timers have to use CLOCK_MONOTONIC to ensure POSIX compliance. The introduction of the additional HRTIMER_MODE_PINNED mode broke this requirement for pinned timers. There is no user space visible impact because user space timers are not using pinned mode, but for consistency reasons this needs to be fixed. Check whether the mode has the HRTIMER_MODE_REL bit set instead of comparing with HRTIMER_MODE_ABS. Signed-off-by:
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Anna-Maria Gleixner authored
The hrtimer_start[_range_ns]() functions start a timer reliably on this CPU only when HRTIMER_MODE_PINNED is set. Furthermore the HRTIMER_MODE_PINNED mode is not considered when a hrtimer is initialized. Signed-off-by:
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Anna-Maria Gleixner authored
schedule_hrtimeout_range_clock() uses an 'int clock' parameter for the clock ID, instead of the customary predefined "clockid_t" type. In hrtimer coding style the canonical variable name for the clock ID is 'clock_id', therefore change the name of the parameter here as well to make it all consistent. While at it, clean up the description for the 'clock_id' and 'mode' function parameters. The clock modes and the clock IDs are not restricted as the comment suggests. Fix the mode description as well for the callers of schedule_hrtimeout_range_clock(). No functional changes intended. Signed-off-by:
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Anna-Maria Gleixner authored
The '/**' sequence marks the start of a structure description. Add the missing second asterisk. While at it adapt the ordering of the struct members to the struct definition and document the purpose of expires_next more precisely. Signed-off-by:
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Thomas Gleixner authored
The protection of a hrtimer which runs its callback against migration to a different CPU has nothing to do with hard interrupt context. The protection against migration of a hrtimer running the expiry callback is the pointer in the cpu_base which holds a pointer to the currently running timer. This pointer is evaluated in the code which potentially switches the timer base and makes sure it's kept on the CPU on which the callback is running. Reported-by:
Frederic Weisbecker <frederic@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: John Stultz <john.stultz@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: keescook@chromium.org Link: http://lkml.kernel.org/r/20171221104205.7269-3-anna-maria@linutronix.de Signed-off-by:
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Thomas Gleixner authored
The hrtimer_cpu_base::migration_enable and ::nohz_active fields were originally introduced to avoid accessing global variables for these decisions. Still that results in a (cache hot) load and conditional branch, which can be avoided by using static keys. Implement it with static keys and optimize for the most critical case of high performance networking which tends to disable the timer migration functionality. No change in functionality. Signed-off-by:
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Ingo Molnar authored
Signed-off-by:
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- Jan 14, 2018
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Thomas Gleixner authored
When the timer base is checked for expired timers then the deferrable base must be checked as well. This was missed when making the deferrable base independent of base::nohz_active. Fixes: ced6d5c1 ("timers: Use deferrable base independent of base::nohz_active") Signed-off-by:
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Max R. P. Grossmann authored
Because the return value of cpu_timer_sample_group() is not checked, compilers and static checkers can legitimately warn about a potential use of the uninitialized variable 'now'. This is not a runtime issue as all call sites hand in valid clock ids. Also cpu_timer_sample_group() is invoked unconditionally even when the result is not used because *oldval is NULL. Make the invocation conditional and check the return value. [ tglx: Massage changelog ] Signed-off-by:
Max R. P. Grossmann <m@max.pm> Signed-off-by:
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- Jan 08, 2018
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Daniel Lezcano authored
As we have a lot of timers on this platform, we can have potentially all the timers enabled in the DT, so we don't want to start the timer for every probe otherwise they will be running for nothing as only one will be used. Start the timer only when setting the mode or when the clocksource is enabled. Tested-by:
Benjamin Gaignard <benjamin.gaignard@st.com> Signed-off-by:
Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by:
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Daniel Lezcano authored
Add the timer delay callback, that saves us ~90ms of boot time. Tested-by:
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Benjamin Gaignard authored
The scene is set for the clocksource functionality, let's add it for this driver. Tested-by:
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Daniel Lezcano authored
In order to prepare the clocksource code, let's factor out the clockevent code, split the prescaler and timer width code into separate functions. Tested-by:
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Benjamin Gaignard authored
The stm32 timer block is able to have a counter and a comparator. Instead of using the auto-reload register for periodic events, we switch to oneshot mode by using the comparator register. The timer is able to generate an interrupt when the counter overflows but we don't want that as this counter will be use as a clocksource in the next patches. So it is disabled by the UDIS bit of the control register. Tested-by:
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Benjamin Gaignard authored
The prescaler value is arbitrarily set to 1024 without any regard to the timer frequency. For 32-bit timers, there is no need to set a prescaler value as they wrap in an acceptable interval and give the opportunity to have precise timers on this platform. However, for 16-bit timers a prescaler value is needed if we don't want to wrap too often per second which is inefficient and adds more and more error margin. With a targeted clock of 10MHz, the 16 bits are precise enough whatever the timer frequency is as we will compute the prescaler. Tested-by:
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Daniel Lezcano authored
In order to clarify and encapsulate the code for upcoming changes, move the timer width check into a function and add some documentation. Tested-by:
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Daniel Lezcano authored
As there are different timers on the stm32, use the node name for the timer name in order to give the indication of which timer the kernel is using. /proc/timer_list gives all the information with the right name, otherwise we end up digging in the kernel log and /proc/interrupt to do the connection between the used timer. Tested-by:
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Benjamin Gaignard authored
Convert the driver to use the timer_of() helpers. This allows the removal of a custom private structure, factors out and simplifies the code. [Daniel Lezcano]: Respin against the critical fix patch and massaged the changelog. Tested-by:
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