DEFINE_PER_CPU(struct context_tracking, context_tracking);
EXPORT_SYMBOL_GPL(context_tracking);
-void context_tracking_cpu_set(int cpu)
+static bool context_tracking_recursion_enter(void)
{
- if (!per_cpu(context_tracking.active, cpu)) {
- per_cpu(context_tracking.active, cpu) = true;
- static_key_slow_inc(&context_tracking_enabled);
- }
+ int recursion;
+
+ recursion = __this_cpu_inc_return(context_tracking.recursion);
+ if (recursion == 1)
+ return true;
+
+ WARN_ONCE((recursion < 1), "Invalid context tracking recursion value %d\n", recursion);
+ __this_cpu_dec(context_tracking.recursion);
+
+ return false;
+}
+
+static void context_tracking_recursion_exit(void)
+{
+ __this_cpu_dec(context_tracking.recursion);
}
/**
* instructions to execute won't use any RCU read side critical section
* because this function sets RCU in extended quiescent state.
*/
-void context_tracking_enter(enum ctx_state state)
+void __context_tracking_enter(enum ctx_state state)
{
- unsigned long flags;
-
- /*
- * Repeat the user_enter() check here because some archs may be calling
- * this from asm and if no CPU needs context tracking, they shouldn't
- * go further. Repeat the check here until they support the inline static
- * key check.
- */
- if (!context_tracking_is_enabled())
- return;
-
- /*
- * Some contexts may involve an exception occuring in an irq,
- * leading to that nesting:
- * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
- * This would mess up the dyntick_nesting count though. And rcu_irq_*()
- * helpers are enough to protect RCU uses inside the exception. So
- * just return immediately if we detect we are in an IRQ.
- */
- if (in_interrupt())
- return;
-
/* Kernel threads aren't supposed to go to userspace */
WARN_ON_ONCE(!current->mm);
- local_irq_save(flags);
+ if (!context_tracking_recursion_enter())
+ return;
+
if ( __this_cpu_read(context_tracking.state) != state) {
if (__this_cpu_read(context_tracking.active)) {
/*
*/
__this_cpu_write(context_tracking.state, state);
}
+ context_tracking_recursion_exit();
+}
+NOKPROBE_SYMBOL(__context_tracking_enter);
+EXPORT_SYMBOL_GPL(__context_tracking_enter);
+
+void context_tracking_enter(enum ctx_state state)
+{
+ unsigned long flags;
+
+ /*
+ * Some contexts may involve an exception occuring in an irq,
+ * leading to that nesting:
+ * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
+ * This would mess up the dyntick_nesting count though. And rcu_irq_*()
+ * helpers are enough to protect RCU uses inside the exception. So
+ * just return immediately if we detect we are in an IRQ.
+ */
+ if (in_interrupt())
+ return;
+
+ local_irq_save(flags);
+ __context_tracking_enter(state);
local_irq_restore(flags);
}
NOKPROBE_SYMBOL(context_tracking_enter);
void context_tracking_user_enter(void)
{
- context_tracking_enter(CONTEXT_USER);
+ user_enter();
}
NOKPROBE_SYMBOL(context_tracking_user_enter);
* This call supports re-entrancy. This way it can be called from any exception
* handler without needing to know if we came from userspace or not.
*/
-void context_tracking_exit(enum ctx_state state)
+void __context_tracking_exit(enum ctx_state state)
{
- unsigned long flags;
-
- if (!context_tracking_is_enabled())
+ if (!context_tracking_recursion_enter())
return;
- if (in_interrupt())
- return;
-
- local_irq_save(flags);
if (__this_cpu_read(context_tracking.state) == state) {
if (__this_cpu_read(context_tracking.active)) {
/*
}
__this_cpu_write(context_tracking.state, CONTEXT_KERNEL);
}
+ context_tracking_recursion_exit();
+}
+NOKPROBE_SYMBOL(__context_tracking_exit);
+EXPORT_SYMBOL_GPL(__context_tracking_exit);
+
+void context_tracking_exit(enum ctx_state state)
+{
+ unsigned long flags;
+
+ if (in_interrupt())
+ return;
+
+ local_irq_save(flags);
+ __context_tracking_exit(state);
local_irq_restore(flags);
}
NOKPROBE_SYMBOL(context_tracking_exit);
void context_tracking_user_exit(void)
{
- context_tracking_exit(CONTEXT_USER);
+ user_exit();
}
NOKPROBE_SYMBOL(context_tracking_user_exit);
-/**
- * __context_tracking_task_switch - context switch the syscall callbacks
- * @prev: the task that is being switched out
- * @next: the task that is being switched in
- *
- * The context tracking uses the syscall slow path to implement its user-kernel
- * boundaries probes on syscalls. This way it doesn't impact the syscall fast
- * path on CPUs that don't do context tracking.
- *
- * But we need to clear the flag on the previous task because it may later
- * migrate to some CPU that doesn't do the context tracking. As such the TIF
- * flag may not be desired there.
- */
-void __context_tracking_task_switch(struct task_struct *prev,
- struct task_struct *next)
+void __init context_tracking_cpu_set(int cpu)
{
- clear_tsk_thread_flag(prev, TIF_NOHZ);
- set_tsk_thread_flag(next, TIF_NOHZ);
+ static __initdata bool initialized = false;
+
+ if (!per_cpu(context_tracking.active, cpu)) {
+ per_cpu(context_tracking.active, cpu) = true;
+ static_key_slow_inc(&context_tracking_enabled);
+ }
+
+ if (initialized)
+ return;
+
+ /*
+ * Set TIF_NOHZ to init/0 and let it propagate to all tasks through fork
+ * This assumes that init is the only task at this early boot stage.
+ */
+ set_tsk_thread_flag(&init_task, TIF_NOHZ);
+ WARN_ON_ONCE(!tasklist_empty());
+
+ initialized = true;
}
#ifdef CONFIG_CONTEXT_TRACKING_FORCE
Code Review / kvmfornfv.git / blobdiff