The following commit has been merged into the sched/urgent branch of tip: Commit-ID: ad6567b439016f9ffd01bbb25276ee363d9a106a Gitweb: https://git.kernel.org/tip/ad6567b439016f9ffd01bbb25276ee363d9a106a Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Mon, 22 Jun 2020 12:01:25 +02:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Mon, 22 Jun 2020 20:51:06 +02:00 smp, irq_work: Continue smp_call_function*() and irq_work*() integration Instead of relying on BUG_ON() to ensure the various data structures line up, use a bunch of horrible unions. Much of the union magic is to ensure irq_work and smp_call_function do not (yet) see the members of their respective data structures change name. Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20200622100825.844455025@xxxxxxxxxxxxx --- include/linux/irq_work.h | 26 ++++----------- include/linux/sched.h | 5 +--- include/linux/smp.h | 23 ++++--------- include/linux/smp_types.h | 66 ++++++++++++++++++++++++++++++++++++++- kernel/sched/core.c | 6 +-- kernel/smp.c | 18 +---------- 6 files changed, 86 insertions(+), 58 deletions(-) create mode 100644 include/linux/smp_types.h diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h index 2735da5..3082378 100644 --- a/include/linux/irq_work.h +++ b/include/linux/irq_work.h @@ -2,7 +2,7 @@ #ifndef _LINUX_IRQ_WORK_H #define _LINUX_IRQ_WORK_H -#include <linux/llist.h> +#include <linux/smp_types.h> /* * An entry can be in one of four states: @@ -13,24 +13,14 @@ * busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed */ -/* flags share CSD_FLAG_ space */ - -#define IRQ_WORK_PENDING BIT(0) -#define IRQ_WORK_BUSY BIT(1) - -/* Doesn't want IPI, wait for tick: */ -#define IRQ_WORK_LAZY BIT(2) -/* Run hard IRQ context, even on RT */ -#define IRQ_WORK_HARD_IRQ BIT(3) - -#define IRQ_WORK_CLAIMED (IRQ_WORK_PENDING | IRQ_WORK_BUSY) - -/* - * structure shares layout with single_call_data_t. - */ struct irq_work { - struct llist_node llnode; - atomic_t flags; + union { + struct __call_single_node node; + struct { + struct llist_node llnode; + atomic_t flags; + }; + }; void (*func)(struct irq_work *); }; diff --git a/include/linux/sched.h b/include/linux/sched.h index 59caeb9..0376588 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -653,11 +653,8 @@ struct task_struct { unsigned int ptrace; #ifdef CONFIG_SMP - struct { - struct llist_node wake_entry; - unsigned int wake_entry_type; - }; int on_cpu; + struct __call_single_node wake_entry; #ifdef CONFIG_THREAD_INFO_IN_TASK /* Current CPU: */ unsigned int cpu; diff --git a/include/linux/smp.h b/include/linux/smp.h index 7ee202a..80d557e 100644 --- a/include/linux/smp.h +++ b/include/linux/smp.h @@ -12,29 +12,22 @@ #include <linux/list.h> #include <linux/cpumask.h> #include <linux/init.h> -#include <linux/llist.h> +#include <linux/smp_types.h> typedef void (*smp_call_func_t)(void *info); typedef bool (*smp_cond_func_t)(int cpu, void *info); -enum { - CSD_FLAG_LOCK = 0x01, - - /* IRQ_WORK_flags */ - - CSD_TYPE_ASYNC = 0x00, - CSD_TYPE_SYNC = 0x10, - CSD_TYPE_IRQ_WORK = 0x20, - CSD_TYPE_TTWU = 0x30, - CSD_FLAG_TYPE_MASK = 0xF0, -}; - /* * structure shares (partial) layout with struct irq_work */ struct __call_single_data { - struct llist_node llist; - unsigned int flags; + union { + struct __call_single_node node; + struct { + struct llist_node llist; + unsigned int flags; + }; + }; smp_call_func_t func; void *info; }; diff --git a/include/linux/smp_types.h b/include/linux/smp_types.h new file mode 100644 index 0000000..364b3ae --- /dev/null +++ b/include/linux/smp_types.h @@ -0,0 +1,66 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __LINUX_SMP_TYPES_H +#define __LINUX_SMP_TYPES_H + +#include <linux/llist.h> + +enum { + CSD_FLAG_LOCK = 0x01, + + IRQ_WORK_PENDING = 0x01, + IRQ_WORK_BUSY = 0x02, + IRQ_WORK_LAZY = 0x04, /* No IPI, wait for tick */ + IRQ_WORK_HARD_IRQ = 0x08, /* IRQ context on PREEMPT_RT */ + + IRQ_WORK_CLAIMED = (IRQ_WORK_PENDING | IRQ_WORK_BUSY), + + CSD_TYPE_ASYNC = 0x00, + CSD_TYPE_SYNC = 0x10, + CSD_TYPE_IRQ_WORK = 0x20, + CSD_TYPE_TTWU = 0x30, + + CSD_FLAG_TYPE_MASK = 0xF0, +}; + +/* + * struct __call_single_node is the primary type on + * smp.c:call_single_queue. + * + * flush_smp_call_function_queue() only reads the type from + * __call_single_node::u_flags as a regular load, the above + * (anonymous) enum defines all the bits of this word. + * + * Other bits are not modified until the type is known. + * + * CSD_TYPE_SYNC/ASYNC: + * struct { + * struct llist_node node; + * unsigned int flags; + * smp_call_func_t func; + * void *info; + * }; + * + * CSD_TYPE_IRQ_WORK: + * struct { + * struct llist_node node; + * atomic_t flags; + * void (*func)(struct irq_work *); + * }; + * + * CSD_TYPE_TTWU: + * struct { + * struct llist_node node; + * unsigned int flags; + * }; + * + */ + +struct __call_single_node { + struct llist_node llist; + union { + unsigned int u_flags; + atomic_t a_flags; + }; +}; + +#endif /* __LINUX_SMP_TYPES_H */ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 019db7a..1339440 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2293,7 +2293,7 @@ void sched_ttwu_pending(void *arg) rq_lock_irqsave(rq, &rf); update_rq_clock(rq); - llist_for_each_entry_safe(p, t, llist, wake_entry) { + llist_for_each_entry_safe(p, t, llist, wake_entry.llist) { if (WARN_ON_ONCE(p->on_cpu)) smp_cond_load_acquire(&p->on_cpu, !VAL); @@ -2329,7 +2329,7 @@ static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); WRITE_ONCE(rq->ttwu_pending, 1); - __smp_call_single_queue(cpu, &p->wake_entry); + __smp_call_single_queue(cpu, &p->wake_entry.llist); } void wake_up_if_idle(int cpu) @@ -2786,7 +2786,7 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) #endif init_numa_balancing(clone_flags, p); #ifdef CONFIG_SMP - p->wake_entry_type = CSD_TYPE_TTWU; + p->wake_entry.u_flags = CSD_TYPE_TTWU; #endif } diff --git a/kernel/smp.c b/kernel/smp.c index 472c2b2..aa17eed 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -669,24 +669,6 @@ void __init smp_init(void) { int num_nodes, num_cpus; - /* - * Ensure struct irq_work layout matches so that - * flush_smp_call_function_queue() can do horrible things. - */ - BUILD_BUG_ON(offsetof(struct irq_work, llnode) != - offsetof(struct __call_single_data, llist)); - BUILD_BUG_ON(offsetof(struct irq_work, func) != - offsetof(struct __call_single_data, func)); - BUILD_BUG_ON(offsetof(struct irq_work, flags) != - offsetof(struct __call_single_data, flags)); - - /* - * Assert the CSD_TYPE_TTWU layout is similar enough - * for task_struct to be on the @call_single_queue. - */ - BUILD_BUG_ON(offsetof(struct task_struct, wake_entry_type) - offsetof(struct task_struct, wake_entry) != - offsetof(struct __call_single_data, flags) - offsetof(struct __call_single_data, llist)); - idle_threads_init(); cpuhp_threads_init();
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