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-rw-r--r--include/linux/context_tracking.h4
-rw-r--r--include/linux/init_task.h2
-rw-r--r--include/linux/sched.h11
-rw-r--r--include/linux/stop_machine.h7
-rw-r--r--include/linux/vtime.h25
-rw-r--r--include/linux/wait.h30
6 files changed, 63 insertions, 16 deletions
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 68b575afe5f5..d259274238db 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -86,7 +86,7 @@ static inline void context_tracking_init(void) { }
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
static inline void guest_enter(void)
{
- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_guest_enter(current);
else
current->flags |= PF_VCPU;
@@ -100,7 +100,7 @@ static inline void guest_exit(void)
if (context_tracking_is_enabled())
__context_tracking_exit(CONTEXT_GUEST);
- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_guest_exit(current);
else
current->flags &= ~PF_VCPU;
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 1c1ff7e4faa4..f2cb8d45513d 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -150,7 +150,7 @@ extern struct task_group root_task_group;
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
# define INIT_VTIME(tsk) \
- .vtime_seqlock = __SEQLOCK_UNLOCKED(tsk.vtime_seqlock), \
+ .vtime_seqcount = SEQCNT_ZERO(tsk.vtime_seqcount), \
.vtime_snap = 0, \
.vtime_snap_whence = VTIME_SYS,
#else
diff --git a/include/linux/sched.h b/include/linux/sched.h
index fa39434e3fdd..791b47e40317 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -177,9 +177,9 @@ extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load);
extern void calc_global_load(unsigned long ticks);
#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
-extern void update_cpu_load_nohz(void);
+extern void update_cpu_load_nohz(int active);
#else
-static inline void update_cpu_load_nohz(void) { }
+static inline void update_cpu_load_nohz(int active) { }
#endif
extern unsigned long get_parent_ip(unsigned long addr);
@@ -1520,11 +1520,14 @@ struct task_struct {
cputime_t gtime;
struct prev_cputime prev_cputime;
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
- seqlock_t vtime_seqlock;
+ seqcount_t vtime_seqcount;
unsigned long long vtime_snap;
enum {
- VTIME_SLEEPING = 0,
+ /* Task is sleeping or running in a CPU with VTIME inactive */
+ VTIME_INACTIVE = 0,
+ /* Task runs in userspace in a CPU with VTIME active */
VTIME_USER,
+ /* Task runs in kernelspace in a CPU with VTIME active */
VTIME_SYS,
} vtime_snap_whence;
#endif
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 0e1b1540597a..3cc9632dcc2a 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -29,7 +29,7 @@ struct cpu_stop_work {
int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
-void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf);
int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
@@ -65,7 +65,7 @@ static void stop_one_cpu_nowait_workfn(struct work_struct *work)
preempt_enable();
}
-static inline void stop_one_cpu_nowait(unsigned int cpu,
+static inline bool stop_one_cpu_nowait(unsigned int cpu,
cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf)
{
@@ -74,7 +74,10 @@ static inline void stop_one_cpu_nowait(unsigned int cpu,
work_buf->fn = fn;
work_buf->arg = arg;
schedule_work(&work_buf->work);
+ return true;
}
+
+ return false;
}
static inline int stop_cpus(const struct cpumask *cpumask,
diff --git a/include/linux/vtime.h b/include/linux/vtime.h
index c5165fd256f9..fa2196990f84 100644
--- a/include/linux/vtime.h
+++ b/include/linux/vtime.h
@@ -10,16 +10,27 @@
struct task_struct;
/*
- * vtime_accounting_enabled() definitions/declarations
+ * vtime_accounting_cpu_enabled() definitions/declarations
*/
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
-static inline bool vtime_accounting_enabled(void) { return true; }
+static inline bool vtime_accounting_cpu_enabled(void) { return true; }
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
+/*
+ * Checks if vtime is enabled on some CPU. Cputime readers want to be careful
+ * in that case and compute the tickless cputime.
+ * For now vtime state is tied to context tracking. We might want to decouple
+ * those later if necessary.
+ */
static inline bool vtime_accounting_enabled(void)
{
- if (context_tracking_is_enabled()) {
+ return context_tracking_is_enabled();
+}
+
+static inline bool vtime_accounting_cpu_enabled(void)
+{
+ if (vtime_accounting_enabled()) {
if (context_tracking_cpu_is_enabled())
return true;
}
@@ -29,7 +40,7 @@ static inline bool vtime_accounting_enabled(void)
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
-static inline bool vtime_accounting_enabled(void) { return false; }
+static inline bool vtime_accounting_cpu_enabled(void) { return false; }
#endif /* !CONFIG_VIRT_CPU_ACCOUNTING */
@@ -44,7 +55,7 @@ extern void vtime_task_switch(struct task_struct *prev);
extern void vtime_common_task_switch(struct task_struct *prev);
static inline void vtime_task_switch(struct task_struct *prev)
{
- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_common_task_switch(prev);
}
#endif /* __ARCH_HAS_VTIME_TASK_SWITCH */
@@ -59,7 +70,7 @@ extern void vtime_account_irq_enter(struct task_struct *tsk);
extern void vtime_common_account_irq_enter(struct task_struct *tsk);
static inline void vtime_account_irq_enter(struct task_struct *tsk)
{
- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_common_account_irq_enter(tsk);
}
#endif /* __ARCH_HAS_VTIME_ACCOUNT */
@@ -78,7 +89,7 @@ extern void vtime_gen_account_irq_exit(struct task_struct *tsk);
static inline void vtime_account_irq_exit(struct task_struct *tsk)
{
- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_gen_account_irq_exit(tsk);
}
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 513b36f04dfd..d2f4ec7dba7c 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -102,6 +102,36 @@ init_waitqueue_func_entry(wait_queue_t *q, wait_queue_func_t func)
q->func = func;
}
+/**
+ * waitqueue_active -- locklessly test for waiters on the queue
+ * @q: the waitqueue to test for waiters
+ *
+ * returns true if the wait list is not empty
+ *
+ * NOTE: this function is lockless and requires care, incorrect usage _will_
+ * lead to sporadic and non-obvious failure.
+ *
+ * Use either while holding wait_queue_head_t::lock or when used for wakeups
+ * with an extra smp_mb() like:
+ *
+ * CPU0 - waker CPU1 - waiter
+ *
+ * for (;;) {
+ * @cond = true; prepare_to_wait(&wq, &wait, state);
+ * smp_mb(); // smp_mb() from set_current_state()
+ * if (waitqueue_active(wq)) if (@cond)
+ * wake_up(wq); break;
+ * schedule();
+ * }
+ * finish_wait(&wq, &wait);
+ *
+ * Because without the explicit smp_mb() it's possible for the
+ * waitqueue_active() load to get hoisted over the @cond store such that we'll
+ * observe an empty wait list while the waiter might not observe @cond.
+ *
+ * Also note that this 'optimization' trades a spin_lock() for an smp_mb(),
+ * which (when the lock is uncontended) are of roughly equal cost.
+ */
static inline int waitqueue_active(wait_queue_head_t *q)
{
return !list_empty(&q->task_list);
generated by cgit (git 2.34.1) at 2024-06-25 10:38:40 +0000