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kernel: Remove possibility to yield to all threads 

Kernel support for yielding to all (including lower priority) threads
has been removed. POSIX sched_yield() remains unchanged.

If a thread really needs to yield to everyone it can reduce its priority
to the lowest possible and then yield (it will then need to manually
return to its prvious priority upon continuing).
This commit is contained in:
Pawel Dziepak 2013-10-09 20:42:34 +02:00
parent fee8009184
commit 29e65827fd
7 changed files with 12 additions and 92 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
headers/private/kernel/thread.h
View File

@ -86,7 +86,7 @@ void thread_reset_for_exec(void);
status_t thread_init(struct kernel_args *args);
status_t thread_preboot_init_percpu(struct kernel_args *args, int32 cpuNum);
void thread_yield(bool force);
void thread_yield(void);
void thread_exit(void);
int32 thread_max_threads(void);

1
headers/private/kernel/thread_types.h
View File

@ -444,7 +444,6 @@ struct Thread : TeamThreadIteratorEntry<thread_id>, KernelReferenceable,
bool in_kernel; // protected by time_lock, only written by
// this thread
bool has_yielded; // protected by scheduler lock
bool has_fully_yielded; // protected by scheduler lock
struct scheduler_thread_data* scheduler_data; // protected by scheduler lock
struct user_thread* user_thread; // write-protected by fLock, only

2
src/add-ons/kernel/bus_managers/random/yarrow_rng.cpp
View File

@ -158,7 +158,7 @@ reseed(ch_randgen *prandgen, const uint32 initTimes)
// random seed on startup by reading from /dev/urandom, perl
// programs are all but unusable when at least one other thread
// hogs the CPU.
thread_yield(false);
thread_yield();
// TODO: Introduce a clock_counter() function that directly returns
// the value of the hardware clock counter. This will be cheaper

2
src/system/kernel/arch/x86/arch_cpu.cpp
View File

@ -155,7 +155,7 @@ acpi_shutdown(bool rebootSystem)
_user_set_cpu_enabled(cpu, false);
}
// TODO: must not be called from the idle thread!
thread_yield(true);
thread_yield();
status = acpi->prepare_sleep_state(ACPI_POWER_STATE_OFF, NULL, 0);
if (status == B_OK) {

83
src/system/kernel/scheduler/scheduler_simple.cpp
View File

@ -46,8 +46,6 @@ const bigtime_t kThreadQuantum = 1000;
// The run queue. Holds the threads ready to run ordered by priority.
typedef RunQueue<Thread, THREAD_MAX_SET_PRIORITY> SimpleRunQueue;
static SimpleRunQueue* sRunQueue;
static SimpleRunQueue* sExpiredQueue;
static int32 sYieldedThreadPriority = -1;
struct scheduler_thread_data {
@ -56,7 +54,6 @@ struct scheduler_thread_data {
int32 priority_penalty;
int32 additional_penalty;
int32 forced_yield_count;
bool lost_cpu;
bool cpu_bound;
@ -74,7 +71,6 @@ scheduler_thread_data::Init()
{
priority_penalty = 0;
additional_penalty = 0;
forced_yield_count = 0;
time_left = 0;
stolen_time = 0;
@ -133,10 +129,6 @@ dump_run_queue(int argc, char** argv)
iterator = sRunQueue->GetConstIterator();
dump_queue(iterator);
kprintf("\nExpired run queue:\n");
iterator = sExpiredQueue->GetConstIterator();
dump_queue(iterator);
return 0;
}
@ -157,8 +149,6 @@ simple_dump_thread_data(Thread* thread)
}
kprintf("\tadditional_penalty:\t%" B_PRId32 " (%" B_PRId32 ")\n",
additionalPenalty, schedulerThreadData->additional_penalty);
kprintf("\tforced_yield_count:\t%" B_PRId32 "\n",
schedulerThreadData->forced_yield_count);
kprintf("\tstolen_time:\t\t%" B_PRId64 "\n",
schedulerThreadData->stolen_time);
}
@ -182,28 +172,6 @@ simple_get_effective_priority(Thread* thread)
}
static inline void
simple_yield(Thread* thread)
{
TRACE("thread %ld yielded\n", thread->id);
int32 effectivePriority = simple_get_effective_priority(thread);
sYieldedThreadPriority = max_c(sYieldedThreadPriority, effectivePriority);
}
static inline bool
simple_should_force_yield(Thread* thread)
{
if (thread->priority >= B_FIRST_REAL_TIME_PRIORITY)
return false;
const int kYieldFrequency = 1 << (min_c(thread->priority, 25) / 5 + 1);
return thread->scheduler_data->forced_yield_count != 0
&& thread->scheduler_data->forced_yield_count % kYieldFrequency == 0;
}
static inline void
simple_increase_penalty(Thread* thread)
{
@ -221,7 +189,6 @@ simple_increase_penalty(Thread* thread)
const int kMinimalPriority = simple_get_minimal_priority(thread);
if (thread->priority - oldPenalty <= kMinimalPriority) {
schedulerThreadData->priority_penalty = oldPenalty;
schedulerThreadData->forced_yield_count++;
schedulerThreadData->additional_penalty++;
}
}
@ -236,7 +203,6 @@ simple_cancel_penalty(Thread* thread)
TRACE("cancelling thread %ld penalty\n", thread->id);
schedulerThreadData->priority_penalty = 0;
schedulerThreadData->additional_penalty = 0;
schedulerThreadData->forced_yield_count = 0;
}
@ -251,16 +217,10 @@ simple_enqueue(Thread* thread, bool newOne)
if (newOne && hasSlept > kThreadQuantum)
simple_cancel_penalty(thread);
if (simple_should_force_yield(thread))
simple_yield(thread);
int32 threadPriority = simple_get_effective_priority(thread);
T(EnqueueThread(thread, threadPriority));
if (threadPriority <= sYieldedThreadPriority)
sExpiredQueue->PushBack(thread, threadPriority);
else
sRunQueue->PushBack(thread, threadPriority);
sRunQueue->PushBack(thread, threadPriority);
schedulerThreadData->cpu_bound = true;
schedulerThreadData->time_left = 0;
@ -429,35 +389,6 @@ simple_compute_quantum(Thread* thread)
}
static inline Thread*
simple_get_next_thread(void)
{
Thread* thread;
do {
thread = sRunQueue->PeekMaximum();
if (sYieldedThreadPriority >= 0 && thread != NULL
&& thread_is_idle_thread(thread)) {
sRunQueue->Remove(thread);
simple_enqueue_in_run_queue(thread);
continue;
}
break;
} while (true);
if (thread == NULL && sYieldedThreadPriority >= 0) {
SimpleRunQueue* temp = sRunQueue;
sRunQueue = sExpiredQueue;
sExpiredQueue = temp;
sYieldedThreadPriority = -1;
thread = sRunQueue->PeekMaximum();
}
return thread;
}
/*! Runs the scheduler.
Note: expects thread spinlock to be held
*/
@ -493,9 +424,6 @@ simple_reschedule(void)
if (schedulerOldThreadData->cpu_bound)
simple_increase_penalty(oldThread);
if (oldThread->has_fully_yielded)
simple_yield(oldThread);
TRACE("enqueueing thread %ld into run queue priority = %ld\n",
oldThread->id, simple_get_effective_priority(oldThread));
simple_enqueue(oldThread, false);
@ -521,11 +449,10 @@ simple_reschedule(void)
}
oldThread->has_yielded = false;
oldThread->has_fully_yielded = false;
schedulerOldThreadData->lost_cpu = false;
// select thread with the biggest priority
Thread* nextThread = simple_get_next_thread();
Thread* nextThread = sRunQueue->PeekMaximum();
if (!nextThread)
panic("reschedule(): run queues are empty!\n");
sRunQueue->Remove(nextThread);
@ -634,11 +561,6 @@ scheduler_simple_init()
return B_NO_MEMORY;
ObjectDeleter<SimpleRunQueue> runQueueDeleter(sRunQueue);
sExpiredQueue = new(std::nothrow) SimpleRunQueue;
if (sExpiredQueue == NULL)
return B_NO_MEMORY;
ObjectDeleter<SimpleRunQueue> expiredQueueDeleter(sExpiredQueue);
status_t result = sRunQueue->GetInitStatus();
if (result != B_OK)
return result;
@ -649,6 +571,5 @@ scheduler_simple_init()
"List threads in run queue", "\nLists threads in run queue", 0);
runQueueDeleter.Detach();
expiredQueueDeleter.Detach();
return B_OK;
}

12
src/system/kernel/thread.cpp
View File

@ -179,7 +179,6 @@ Thread::Thread(const char* name, thread_id threadID, struct cpu_ent* cpu)
signal_stack_enabled(false),
in_kernel(true),
has_yielded(false),
has_fully_yielded(false),
user_thread(NULL),
fault_handler(0),
page_faults_allowed(1),
@ -2440,14 +2439,15 @@ peek_next_thread_id()
/*! Yield the CPU to other threads.
If \a force is \c true, the thread will almost guaranteedly be unscheduled.
If \c false, it will continue to run, if there's no other thread in ready
Thread will continue to run, if there's no other thread in ready
state, and if it has a higher priority than the other ready threads, it
still has a good chance to continue.
*/
void
thread_yield(bool force)
thread_yield(void)
{
// Yielding is for being nice, not for making things work.
#if !KDEBUG
Thread *thread = thread_get_current_thread();
if (thread == NULL)
return;
@ -2455,8 +2455,8 @@ thread_yield(bool force)
InterruptsSpinLocker _(gSchedulerLock);
thread->has_yielded = true;
thread->has_fully_yielded = force;
scheduler_reschedule();
#endif
}
@ -3507,7 +3507,7 @@ _user_snooze_etc(bigtime_t timeout, int timebase, uint32 flags,
void
_user_thread_yield(void)
{
thread_yield(false);
thread_yield();
}

2
src/system/kernel/vm/vm_page.cpp
View File

@ -2390,7 +2390,7 @@ page_writer(void* /*unused*/)
if (cache->AcquireUnreferencedStoreRef() != B_OK) {
DEBUG_PAGE_ACCESS_END(page);
cacheLocker.Unlock();
thread_yield(true);
thread_yield();
continue;
}