From 5280a14a6079040205a1d968cd80f20448d047c7 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 15 Oct 2024 12:09:32 -0700 Subject: genirq: Introduce irq_get_nr_irqs() and irq_set_nr_irqs() Prepare for changing 'nr_irqs' from an exported global variable into a variable with file scope. This will prevent accidental changes of assignments to a local variable 'nr_irqs' into assignments to the global 'nr_irqs' variable. Suppose that a patch would be submitted for review that removes a declaration of a local variable with the name 'nr_irqs' and that that patch does not remove all assignments to that local variable. Such a patch converts an assignment to a local variable into an assignment into a global variable. If the 'nr_irqs' assignment is more than three lines away from other changes, the assignment won't be included in the diff context lines and hence won't be visible without inspecting the modified file. With these abstraction series applied, such accidental conversions from assignments to a local variable into an assignment to a global variable are converted into a compilation error. Signed-off-by: Bart Van Assche Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20241015190953.1266194-2-bvanassche@acm.org --- include/linux/irqnr.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/irqnr.h b/include/linux/irqnr.h index 3496baa0b07f..7419b807b71b 100644 --- a/include/linux/irqnr.h +++ b/include/linux/irqnr.h @@ -6,6 +6,8 @@ extern int nr_irqs; +unsigned int irq_get_nr_irqs(void) __pure; +unsigned int irq_set_nr_irqs(unsigned int nr); extern struct irq_desc *irq_to_desc(unsigned int irq); unsigned int irq_get_next_irq(unsigned int offset); -- cgit v1.2.3 From 1ad2048bf7146efb83bc033147ca1611a7fe8494 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 15 Oct 2024 12:09:52 -0700 Subject: genirq: Switch to irq_get_nr_irqs() Use the irq_get_nr_irqs() function instead of the global variable 'nr_irqs'. Cache the result of this function in a local variable in order not to rely on CSE (common subexpression elimination). Prepare for changing 'nr_irqs' from an exported global variable into a variable with file scope. Signed-off-by: Bart Van Assche Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20241015190953.1266194-22-bvanassche@acm.org --- include/linux/irqnr.h | 33 +++++++++++++++++++-------------- 1 file changed, 19 insertions(+), 14 deletions(-) (limited to 'include') diff --git a/include/linux/irqnr.h b/include/linux/irqnr.h index 7419b807b71b..a33088d27c54 100644 --- a/include/linux/irqnr.h +++ b/include/linux/irqnr.h @@ -11,26 +11,31 @@ unsigned int irq_set_nr_irqs(unsigned int nr); extern struct irq_desc *irq_to_desc(unsigned int irq); unsigned int irq_get_next_irq(unsigned int offset); -# define for_each_irq_desc(irq, desc) \ - for (irq = 0, desc = irq_to_desc(irq); irq < nr_irqs; \ - irq++, desc = irq_to_desc(irq)) \ - if (!desc) \ - ; \ - else - +#define for_each_irq_desc(irq, desc) \ + for (unsigned int __nr_irqs__ = irq_get_nr_irqs(); __nr_irqs__; \ + __nr_irqs__ = 0) \ + for (irq = 0, desc = irq_to_desc(irq); irq < __nr_irqs__; \ + irq++, desc = irq_to_desc(irq)) \ + if (!desc) \ + ; \ + else # define for_each_irq_desc_reverse(irq, desc) \ - for (irq = nr_irqs - 1, desc = irq_to_desc(irq); irq >= 0; \ - irq--, desc = irq_to_desc(irq)) \ + for (irq = irq_get_nr_irqs() - 1, desc = irq_to_desc(irq); \ + irq >= 0; irq--, desc = irq_to_desc(irq)) \ if (!desc) \ ; \ else -# define for_each_active_irq(irq) \ - for (irq = irq_get_next_irq(0); irq < nr_irqs; \ - irq = irq_get_next_irq(irq + 1)) +#define for_each_active_irq(irq) \ + for (unsigned int __nr_irqs__ = irq_get_nr_irqs(); __nr_irqs__; \ + __nr_irqs__ = 0) \ + for (irq = irq_get_next_irq(0); irq < __nr_irqs__; \ + irq = irq_get_next_irq(irq + 1)) -#define for_each_irq_nr(irq) \ - for (irq = 0; irq < nr_irqs; irq++) +#define for_each_irq_nr(irq) \ + for (unsigned int __nr_irqs__ = irq_get_nr_irqs(); __nr_irqs__; \ + __nr_irqs__ = 0) \ + for (irq = 0; irq < __nr_irqs__; irq++) #endif -- cgit v1.2.3 From ef4c675dc2961ee533bdc1ea20390761df0af5be Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 15 Oct 2024 12:09:53 -0700 Subject: genirq: Unexport nr_irqs Unexport nr_irqs and declare it static now that all code that reads or modifies nr_irqs has been converted to number_of_interrupts() / set_number_of_interrupts(). Change the type of 'nr_irqs' from 'int' into 'unsigned int' to match the return type and argument type of the irq_get_nr_iqs() / irq_set_nr_irqs() functions. Signed-off-by: Bart Van Assche Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20241015190953.1266194-23-bvanassche@acm.org --- include/linux/irqnr.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include') diff --git a/include/linux/irqnr.h b/include/linux/irqnr.h index a33088d27c54..e97206c721a0 100644 --- a/include/linux/irqnr.h +++ b/include/linux/irqnr.h @@ -5,7 +5,6 @@ #include -extern int nr_irqs; unsigned int irq_get_nr_irqs(void) __pure; unsigned int irq_set_nr_irqs(unsigned int nr); extern struct irq_desc *irq_to_desc(unsigned int irq); -- cgit v1.2.3 From 25caea955cc950507d179f3ef456404b475e8c23 Mon Sep 17 00:00:00 2001 From: Inochi Amaoto Date: Thu, 31 Oct 2024 14:08:58 +0800 Subject: irqchip: Add T-HEAD C900 ACLINT SSWI driver Add a driver for the T-HEAD C900 ACLINT SSWI device. This device allows the system with T-HEAD cpus to send ipi via fast device interface. Signed-off-by: Inochi Amaoto Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20241031060859.722258-3-inochiama@gmail.com --- include/linux/cpuhotplug.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 2361ed4d2b15..799052249c7b 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -147,6 +147,7 @@ enum cpuhp_state { CPUHP_AP_IRQ_EIOINTC_STARTING, CPUHP_AP_IRQ_AVECINTC_STARTING, CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING, + CPUHP_AP_IRQ_THEAD_ACLINT_SSWI_STARTING, CPUHP_AP_IRQ_RISCV_IMSIC_STARTING, CPUHP_AP_IRQ_RISCV_SBI_IPI_STARTING, CPUHP_AP_ARM_MVEBU_COHERENCY, -- cgit v1.2.3 From 49a17639508c3b35f90ca829e60dddeeeb750e74 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Wed, 6 Nov 2024 15:51:39 +0100 Subject: softirq: Use a dedicated thread for timer wakeups on PREEMPT_RT. The timer and hrtimer soft interrupts are raised in hard interrupt context. With threaded interrupts force enabled or on PREEMPT_RT this leads to waking the ksoftirqd for the processing of the soft interrupt. ksoftirqd runs as SCHED_OTHER task which means it will compete with other tasks for CPU resources. This can introduce long delays for timer processing on heavy loaded systems and is not desired. Split the TIMER_SOFTIRQ and HRTIMER_SOFTIRQ processing into a dedicated timers thread and let it run at the lowest SCHED_FIFO priority. Wake-ups for RT tasks happen from hardirq context so only timer_list timers and hrtimers for "regular" tasks are processed here. The higher priority ensures that wakeups are performed before scheduling SCHED_OTHER tasks. Using a dedicated variable to store the pending softirq bits values ensure that the timer are not accidentally picked up by ksoftirqd and other threaded interrupts. It shouldn't be picked up by ksoftirqd since it runs at lower priority. However if ksoftirqd is already running while a timer fires, then ksoftird will be PI-boosted due to the BH-lock to ktimer's priority. The timer thread can pick up pending softirqs from ksoftirqd but only if the softirq load is high. It is not be desired that the picked up softirqs are processed at SCHED_FIFO priority under high softirq load but this can already happen by a PI-boost by a force-threaded interrupt. [ frederic@kernel.org: rcutorture.c fixes, storm fix by introduction of local_timers_pending() for tick_nohz_next_event() ] [ junxiao.chang@intel.com: Ensure ktimersd gets woken up even if a softirq is currently served. ] Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Reviewed-by: Paul E. McKenney [rcutorture] Reviewed-by: Frederic Weisbecker Link: https://lore.kernel.org/all/20241106150419.2593080-4-bigeasy@linutronix.de --- include/linux/interrupt.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) (limited to 'include') diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index 457151f9f263..8cd9327e4e78 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -616,6 +616,53 @@ extern void __raise_softirq_irqoff(unsigned int nr); extern void raise_softirq_irqoff(unsigned int nr); extern void raise_softirq(unsigned int nr); +/* + * With forced-threaded interrupts enabled a raised softirq is deferred to + * ksoftirqd unless it can be handled within the threaded interrupt. This + * affects timer_list timers and hrtimers which are explicitly marked with + * HRTIMER_MODE_SOFT. + * With PREEMPT_RT enabled more hrtimers are moved to softirq for processing + * which includes all timers which are not explicitly marked HRTIMER_MODE_HARD. + * Userspace controlled timers (like the clock_nanosleep() interface) is divided + * into two categories: Tasks with elevated scheduling policy including + * SCHED_{FIFO|RR|DL} and the remaining scheduling policy. The tasks with the + * elevated scheduling policy are woken up directly from the HARDIRQ while all + * other wake ups are delayed to softirq and so to ksoftirqd. + * + * The ksoftirqd runs at SCHED_OTHER policy at which it should remain since it + * handles the softirq in an overloaded situation (not handled everything + * within its last run). + * If the timers are handled at SCHED_OTHER priority then they competes with all + * other SCHED_OTHER tasks for CPU resources are possibly delayed. + * Moving timers softirqs to a low priority SCHED_FIFO thread instead ensures + * that timer are performed before scheduling any SCHED_OTHER thread. + */ +DECLARE_PER_CPU(struct task_struct *, ktimerd); +DECLARE_PER_CPU(unsigned long, pending_timer_softirq); +void raise_ktimers_thread(unsigned int nr); + +static inline unsigned int local_timers_pending_force_th(void) +{ + return __this_cpu_read(pending_timer_softirq); +} + +static inline void raise_timer_softirq(unsigned int nr) +{ + lockdep_assert_in_irq(); + if (force_irqthreads()) + raise_ktimers_thread(nr); + else + __raise_softirq_irqoff(nr); +} + +static inline unsigned int local_timers_pending(void) +{ + if (force_irqthreads()) + return local_timers_pending_force_th(); + else + return local_softirq_pending(); +} + DECLARE_PER_CPU(struct task_struct *, ksoftirqd); static inline struct task_struct *this_cpu_ksoftirqd(void) -- cgit v1.2.3