/*
* AST_URGENT was detected while in kernel mode
* Called with interrupts disabled, returns the same way
* Must return to caller
*/
void
ast_taken_kernel(void)
{
assert(ml_get_interrupts_enabled() == FALSE);
thread_t thread = current_thread();
/* Idle threads handle preemption themselves */
if ((thread->state & TH_IDLE)) {
ast_off(AST_PREEMPTION);
return;
}
/*
* It's possible for this to be called after AST_URGENT
* has already been handled, due to races in enable_preemption
*/
if (ast_peek(AST_URGENT) != AST_URGENT)
return;
/*
* Don't preempt if the thread is already preparing to block.
* TODO: the thread can cheese this with clear_wait()
*/
if (waitq_wait_possible(thread) == FALSE) {
/* Consume AST_URGENT or the interrupt will call us again */
ast_consume(AST_URGENT);
return;
}
/* TODO: Should we csw_check again to notice if conditions have changed? */
ast_t urgent_reason = ast_consume(AST_PREEMPTION);
assert(urgent_reason & AST_PREEMPT);
counter(c_ast_taken_block++);
thread_block_reason(THREAD_CONTINUE_NULL, NULL, urgent_reason);
assert(ml_get_interrupts_enabled() == FALSE);
}
/*
* Called at splsched.
*/
void
ast_taken(
ast_t reasons,
boolean_t enable
)
{
boolean_t preempt_trap = (reasons == AST_PREEMPTION);
ast_t *myast = ast_pending();
thread_t thread = current_thread();
perfASTCallback perf_hook = perfASTHook;
/*
* CHUD hook - all threads including idle processor threads
*/
if (perf_hook) {
if (*myast & AST_CHUD_ALL) {
(*perf_hook)(reasons, myast);
if (*myast == AST_NONE)
return;
}
}
else
*myast &= ~AST_CHUD_ALL;
reasons &= *myast;
*myast &= ~reasons;
/*
* Handle ASTs for all threads
* except idle processor threads.
*/
if (!(thread->state & TH_IDLE)) {
/*
* Check for urgent preemption.
*/
if ( (reasons & AST_URGENT) &&
waitq_wait_possible(thread) ) {
if (reasons & AST_PREEMPT) {
counter(c_ast_taken_block++);
thread_block_reason(THREAD_CONTINUE_NULL, NULL,
reasons & AST_PREEMPTION);
}
reasons &= ~AST_PREEMPTION;
}
/*
* The kernel preempt traps
* skip all other ASTs.
*/
if (!preempt_trap) {
ml_set_interrupts_enabled(enable);
#ifdef MACH_BSD
/*
* Handle BSD hook.
*/
if (reasons & AST_BSD) {
thread_ast_clear(thread, AST_BSD);
bsd_ast(thread);
}
#endif
#if CONFIG_MACF
/*
* Handle MACF hook.
*/
if (reasons & AST_MACF) {
thread_ast_clear(thread, AST_MACF);
mac_thread_userret(thread);
}
#endif
/*
* Thread APC hook.
*/
if (reasons & AST_APC) {
thread_ast_clear(thread, AST_APC);
special_handler(thread);
}
if (reasons & AST_GUARD) {
thread_ast_clear(thread, AST_GUARD);
guard_ast(thread);
}
if (reasons & AST_LEDGER) {
thread_ast_clear(thread, AST_LEDGER);
ledger_ast(thread);
}
/*
* Kernel Profiling Hook
*/
if (reasons & AST_KPERF) {
thread_ast_clear(thread, AST_KPERF);
chudxnu_thread_ast(thread);
}
#if CONFIG_TELEMETRY
if (reasons & AST_TELEMETRY_ALL) {
boolean_t interrupted_userspace = FALSE;
boolean_t is_windowed = FALSE;
assert((reasons & AST_TELEMETRY_ALL) != AST_TELEMETRY_ALL); /* only one is valid at a time */
interrupted_userspace = (reasons & AST_TELEMETRY_USER) ? TRUE : FALSE;
is_windowed = ((reasons & AST_TELEMETRY_WINDOWED) ? TRUE : FALSE);
thread_ast_clear(thread, AST_TELEMETRY_ALL);
telemetry_ast(thread, interrupted_userspace, is_windowed);
}
#endif
ml_set_interrupts_enabled(FALSE);
#if CONFIG_SCHED_SFI
if (reasons & AST_SFI) {
sfi_ast(thread);
}
#endif
/*
* Check for preemption. Conditions may have changed from when the AST_PREEMPT was originally set.
*/
thread_lock(thread);
if (reasons & AST_PREEMPT)
reasons = csw_check(current_processor(), reasons & AST_QUANTUM);
thread_unlock(thread);
assert(waitq_wait_possible(thread));
if (reasons & AST_PREEMPT) {
counter(c_ast_taken_block++);
thread_block_reason((thread_continue_t)thread_exception_return, NULL, reasons & AST_PREEMPTION);
}
}
}
ml_set_interrupts_enabled(enable);
}
/*
* An AST flag was set while returning to user mode
* Called with interrupts disabled, returns with interrupts enabled
* May call continuation instead of returning
*/
void
ast_taken_user(void)
{
assert(ml_get_interrupts_enabled() == FALSE);
thread_t thread = current_thread();
/* We are about to return to userspace, there must not be a pending wait */
assert(waitq_wait_possible(thread));
assert((thread->state & TH_IDLE) == 0);
/* TODO: Add more 'return to userspace' assertions here */
/*
* If this thread was urgently preempted in userspace,
* take the preemption before processing the ASTs.
* The trap handler will call us again if we have more ASTs, so it's
* safe to block in a continuation here.
*/
if (ast_peek(AST_URGENT) == AST_URGENT) {
ast_t urgent_reason = ast_consume(AST_PREEMPTION);
assert(urgent_reason & AST_PREEMPT);
/* TODO: Should we csw_check again to notice if conditions have changed? */
thread_block_reason(thread_preempted, NULL, urgent_reason);
/* NOTREACHED */
}
/*
* AST_KEVENT does not send an IPI when setting the ast for a thread running in parallel
* on a different processor. Only the ast bit on the thread will be set.
*
* Force a propagate for concurrent updates without an IPI.
*/
ast_propagate(thread);
/*
* Consume all non-preemption processor ASTs matching reasons
* because we're handling them here.
*
* If one of the AST handlers blocks in a continuation,
* we'll reinstate the unserviced thread-level AST flags
* from the thread to the processor on context switch.
* If one of the AST handlers sets another AST,
* the trap handler will call ast_taken_user again.
*
* We expect the AST handlers not to thread_exception_return
* without an ast_propagate or context switch to reinstate
* the per-processor ASTs.
*
* TODO: Why are AST_DTRACE and AST_KPERF not per-thread ASTs?
*/
ast_t reasons = ast_consume(AST_PER_THREAD | AST_KPERF | AST_DTRACE);
ml_set_interrupts_enabled(TRUE);
#if CONFIG_DTRACE
if (reasons & AST_DTRACE) {
dtrace_ast();
}
#endif
#ifdef MACH_BSD
if (reasons & AST_BSD) {
thread_ast_clear(thread, AST_BSD);
bsd_ast(thread);
}
#endif
#if CONFIG_MACF
if (reasons & AST_MACF) {
thread_ast_clear(thread, AST_MACF);
mac_thread_userret(thread);
}
#endif
if (reasons & AST_APC) {
thread_ast_clear(thread, AST_APC);
thread_apc_ast(thread);
}
if (reasons & AST_GUARD) {
thread_ast_clear(thread, AST_GUARD);
guard_ast(thread);
}
if (reasons & AST_LEDGER) {
thread_ast_clear(thread, AST_LEDGER);
ledger_ast(thread);
}
if (reasons & AST_KPERF) {
thread_ast_clear(thread, AST_KPERF);
kperf_kpc_thread_ast(thread);
}
if (reasons & AST_KEVENT) {
thread_ast_clear(thread, AST_KEVENT);
uint16_t bits = atomic_exchange(&thread->kevent_ast_bits, 0);
if (bits) kevent_ast(thread, bits);
}
#if CONFIG_TELEMETRY
if (reasons & AST_TELEMETRY_ALL) {
ast_t telemetry_reasons = reasons & AST_TELEMETRY_ALL;
thread_ast_clear(thread, AST_TELEMETRY_ALL);
telemetry_ast(thread, telemetry_reasons);
}
#endif
spl_t s = splsched();
#if CONFIG_SCHED_SFI
/*
* SFI is currently a per-processor AST, not a per-thread AST
* TODO: SFI should be a per-thread AST
*/
if (ast_consume(AST_SFI) == AST_SFI) {
sfi_ast(thread);
}
#endif
/* We are about to return to userspace, there must not be a pending wait */
assert(waitq_wait_possible(thread));
/*
* We've handled all per-thread ASTs, time to handle non-urgent preemption.
*
* We delay reading the preemption bits until now in case the thread
* blocks while handling per-thread ASTs.
*
* If one of the AST handlers had managed to set a new AST bit,
* thread_exception_return will call ast_taken again.
*/
ast_t preemption_reasons = ast_consume(AST_PREEMPTION);
if (preemption_reasons & AST_PREEMPT) {
/* Conditions may have changed from when the AST_PREEMPT was originally set, so re-check. */
thread_lock(thread);
preemption_reasons = csw_check(current_processor(), (preemption_reasons & AST_QUANTUM));
thread_unlock(thread);
#if CONFIG_SCHED_SFI
/* csw_check might tell us that SFI is needed */
if (preemption_reasons & AST_SFI) {
sfi_ast(thread);
}
#endif
if (preemption_reasons & AST_PREEMPT) {
counter(c_ast_taken_block++);
/* switching to a continuation implicitly re-enables interrupts */
thread_block_reason(thread_preempted, NULL, preemption_reasons);
/* NOTREACHED */
}
}
splx(s);
}