/* unlock_gate
Unlock a gate if it is ours to unlock.
=> gate = lock structure to modify
flags = set either LOCK_READ or LOCK_WRITE, also set LOCK_SELFDESTRUCT
to mark a gate as defunct, causing other threads to fail if
they try to access it
<= success or a failure code
*/
kresult unlock_gate(rw_gate *gate, unsigned int flags)
{
#ifndef UNIPROC
unsigned int caller;
/* sanity checks */
if(!gate) return e_failure;
if(!cpu_table) return success; /* only one processor running */
#ifdef LOCK_DEBUG
if(cpu_table)
{
LOCK_DEBUG("[lock:%i] unlock_gate(%p, %x) by thread %p\n", CPU_ID, gate, flags, cpu_table[CPU_ID].current);
}
else
{
LOCK_DEBUG("[lock:%i] unlock_gate(%p, %x)\n", CPU_ID, gate, flags);
}
#endif
if(cpu_table[CPU_ID].current)
caller = (unsigned int)cpu_table[CPU_ID].current;
else
caller = (CPU_ID) + 1;
lock_spin(&(gate->spinlock));
/* if this is our gate then unset details */
if(gate->owner == caller)
{
/* decrement thread entry count and release the gate if the
owner has completely left, keeping the self-destruct lock
in place if required */
gate->refcount--;
if(gate->refcount == 0)
{
gate->owner = 0;
gate->flags = flags & LOCK_SELFDESTRUCT;
}
}
/* release the gate so others can inspect it */
unlock_spin(&(gate->spinlock));
LOCK_DEBUG("[lock:%i] <- unlocked %p with %x on cpu %i\n", CPU_ID, gate, flags, 0);
return success;
#endif
}
void my_rwlock_destroy(my_rwlock_t * my_rwlock)
{
int semrc = 0;
_MUTEX_DESTROY(my_rwlock->protect_reader_count);
semrc |= sem_destroy(&(my_rwlock->allow_readers));
if(semrc != 0) {
LOCK_DEBUG("rc=%d [%s] RWLOCK DESTROY1", semrc, strerror(errno));
debug_crash();
}
semrc |= sem_destroy(&(my_rwlock->no_processes));
if(semrc != 0) {
LOCK_DEBUG("rc=%d [%s] RWLOCK DESTROY2", semrc, strerror(errno));
debug_crash();
}
memset(my_rwlock, 0, sizeof(my_rwlock_t));
}
/* locks_initialise
Initialise the portable part of the locking system. This will
require setting up locks for the VMM before any of its management
functions can be called using the given physical page
=> initial_phys_pg = base address of first physical page to use
<= 0 for success, or an error code
*/
kresult locks_initialise(void *initial_phys_pg)
{
/* sanity check */
if(!initial_phys_pg) return e_bad_params;
/* zero out the initial pool structure - this VMM call is safe to use.
this also forces gate_pool.prev to be NULL, indicating it's
the first item and therefore shouldn't be free()d */
vmm_memset(&gate_pool, 0, sizeof(rw_gate_pool));
/* plug in the base address of this initial page */
gate_pool.physical_base = initial_phys_pg;
gate_pool.virtual_base = KERNEL_PHYS2LOG(initial_phys_pg);
/* create the first lock by hand - the lock for the locking code */
lock_lock = (rw_gate *)gate_pool.virtual_base;
gate_pool.bitmap[0] = 1; /* too hardcoded? */
gate_pool.last_free = 1;
gate_pool.nr_free = LOCK_POOL_BITMAP_LENGTH_BITS - 1;
vmm_memset(lock_lock, 0, sizeof(rw_gate));
LOCK_DEBUG("[lock:%i] locks initialised: first gate pool at %p, first lock at %p\n",
CPU_ID, &gate_pool, gate_pool.virtual_base);
return success;
}
/* Don't use the builtin rwlock-support in pthread */
void my_rwlock_init(my_rwlock_t * my_rwlock)
{
int semrc = 0;
memset(my_rwlock, 0, sizeof(my_rwlock_t));
_MUTEX_INIT(my_rwlock->protect_reader_count);
semrc |= sem_init(&(my_rwlock->allow_readers), 0, 1);
if(semrc != 0) {
LOCK_DEBUG("rc=%d [%s] RWLOCK INIT1", semrc, strerror(errno));
debug_crash();
}
semrc |= sem_init(&(my_rwlock->no_processes), 0, 1);
if(semrc != 0) {
LOCK_DEBUG("rc=%d [%s] RWLOCK INIT2", semrc, strerror(errno));
debug_crash();
}
my_rwlock->reader_count = 0;
}
void my_rwlock_init(my_rwlock_t * rwlock)
{
int semrc;
semrc = pthread_rwlock_init(rwlock, NULL);
if(semrc != 0) {
LOCK_DEBUG("semrc=%d [%s] RWLOCK INIT", semrc, strerror(errno));
debug_crash();
}
}
int my_rwlock_read_unlock(my_rwlock_t * rwlock)
{
int semrc;
semrc = pthread_rwlock_unlock(rwlock);
if(semrc != 0) {
LOCK_DEBUG("semrc=%d [%s] RWLOCK RUNLOCK", semrc, strerror(errno));
debug_crash();
}
return semrc;
}
void my_rwlock_destroy(my_rwlock_t * rwlock)
{
int semrc;
semrc = pthread_rwlock_destroy(rwlock);
if(semrc != 0) {
/* Might return EBUSY */
LOCK_DEBUG("semrc=%d [%s] RWLOCK DESTROY", semrc, strerror(errno));
debug_crash();
}
}
/* lock_gate_free
Free a readers-writer gate structure
=> ptr = pointer to address of allocated gate
<= 0 for success, or an error code
*/
kresult lock_rw_gate_free(rw_gate *gate)
{
void *page_to_find = MEM_PGALIGN(gate);
unsigned char slot = ((unsigned int)gate - (unsigned int)page_to_find) / sizeof(rw_gate);
/* sanity check */
if(!gate) return e_failure;
/* locate the gate */
rw_gate_pool *search = &gate_pool;
LOCK_DEBUG("[lock:%i] freeing readers-writer gate %p\n", CPU_ID, gate);
/* lock the locking code */
lock_gate(lock_lock, LOCK_WRITE);
while(search)
{
if(search->virtual_base == page_to_find) break;
search = search->next;
}
/* serious problems if a lock's page has gone missing
or the slot bit isn't set.. */
if(!search || !lock_bitmap_test(search->bitmap, slot))
{
unlock_gate(lock_lock, LOCK_WRITE);
return e_not_found;
}
/* clear the slot and free the page if need be */
lock_bitmap_clear(search->bitmap, slot);
search->nr_free++;
search->last_free = slot;
if(search->nr_free == LOCK_POOL_BITMAP_LENGTH_BITS)
{
/* free the page */
vmm_return_phys_pg(search->physical_base);
/* delink from the list */
if(search->next)
search->next->previous = search->previous;
if(search->previous)
search->previous->next = search->next;
vmm_free(search);
}
unlock_gate(lock_lock, LOCK_WRITE);
return success;
}
int my_rwlock_read_unlock(my_rwlock_t * my_rwlock)
{
_MUTEX_LOCK(my_rwlock->protect_reader_count);
if (--my_rwlock->reader_count == 0) {
sem_post(&(my_rwlock->no_processes));
}
if(my_rwlock->reader_count < 0) {
LOCK_DEBUG("RWLOCK RUNLOCK");
debug_crash();
}
_MUTEX_UNLOCK(my_rwlock->protect_reader_count);
return 0;
}
/* LOCKING: this is called with monitor_mutex held */
static void
mon_finalize (MonoThreadsSync *mon)
{
LOCK_DEBUG (g_message ("%s: Finalizing sync %p", __func__, mon));
if (mon->entry_sem != NULL) {
CloseHandle (mon->entry_sem);
mon->entry_sem = NULL;
}
/* If this isn't empty then something is seriously broken - it
* means a thread is still waiting on the object that owned
* this lock, but the object has been finalized.
*/
g_assert (mon->wait_list == NULL);
mon->entry_count = 0;
/* owner and nest are set in mon_new, no need to zero them out */
mon->data = monitor_freelist;
monitor_freelist = mon;
mono_perfcounters->gc_sync_blocks--;
}
/* lock_gate
Allow multiple threads to read during a critical section, but only
allow one writer. To avoid deadlocks, it keeps track of the exclusive
owner - so that a thread can enter a gate as a reader and later
upgrade to a writer, or start off a writer and call a function that
requires a read or write lock. This function will block and spin if
write access is requested and other threads are reading/writing, or
read access is requested and another thread is writing.
=> gate = lock structure to modify
flags = set either LOCK_READ or LOCK_WRITE, also set LOCK_SELFDESTRUCT
to mark a gate as defunct, causing other threads to fail if
they try to access it
<= success or a failure code
*/
kresult lock_gate(rw_gate *gate, unsigned int flags)
{
#ifndef UNIPROC
kresult err = success;
unsigned int caller;
#ifdef LOCK_TIME_CHECK
unsigned long long ticks = x86_read_cyclecount();
#endif
/* sanity checks */
if(!gate) return e_failure;
if(!cpu_table) return success; /* only one processor running */
#ifdef LOCK_DEBUG
if(cpu_table)
{
LOCK_DEBUG("[lock:%i] -> lock_gate(%p, %x) by thread %p\n", CPU_ID, gate, flags, cpu_table[CPU_ID].current);
}
else
{
LOCK_DEBUG("[lock:%i] -> lock_gate(%p, %x) during boot\n", CPU_ID, gate, flags);
}
#endif
/* cpu_table[CPU_ID].current cannot be lower than the kernel virtual base
so it won't collide with the processor's CPU_ID, which is used to
identify the owner if no thread is running */
if(cpu_table[CPU_ID].current)
caller = (unsigned int)cpu_table[CPU_ID].current;
else
caller = (CPU_ID) + 1; /* zero means no owner, CPU_IDs start at zero... */
while(1)
{
lock_spin(&(gate->spinlock));
/* we're in - is the gate claimed? */
if(gate->owner)
{
/* it's in use - but is it another thread? */
if(gate->owner != caller)
{
/* another thread has it :( perform checks */
/* this lock is defunct? */
if(gate->flags & LOCK_SELFDESTRUCT)
{
err = e_failure;
goto exit_lock_gate;
}
/* if we're not trying to write and the owner isn't
writing and a writer isn't waiting, then it's safe to progress */
if(!(flags & LOCK_WRITE) && !(gate->flags & LOCK_WRITE) && !(gate->flags & LOCK_WRITEWAITING))
goto exit_lock_gate;
/* if we're trying to write then set a write-wait flag.
when this flag is set, stop allowing new reading threads.
this should prevent writer starvation */
if(flags & LOCK_WRITE)
gate->flags |= LOCK_WRITEWAITING;
}
else
{
/* if the gate's owned by this thread, then carry on */
gate->refcount++; /* keep track of the number of times we're entering */
goto exit_lock_gate;
}
}
else
{
/* no one owns this gate, so make our mark */
gate->owner = caller;
gate->flags = flags;
gate->refcount = 1; /* first in */
goto exit_lock_gate;
}
unlock_spin(&(gate->spinlock));
/* small window of opportunity for the other thread to
release the gate :-/ */
/* hint to newer processors that this is a spin-wait loop or
NOP for older processors */
__asm__ __volatile__("pause");
#ifdef LOCK_TIME_CHECK
if((x86_read_cyclecount() - ticks) > LOCK_TIMEOUT)
{
/* prevent other cores from trashing the output debug while we dump this info */
lock_spin(&lock_time_check_lock);
KOOPS_DEBUG("[lock:%i] OMGWTF waited too long for gate %p to become available (flags %x)\n"
" lock is owned by %p", CPU_ID, gate, flags, gate->owner);
if(gate->owner > KERNEL_SPACE_BASE)
{
thread *t = (thread *)(gate->owner);
KOOPS_DEBUG(" (thread %i process %i on cpu %i)", t->tid, t->proc->pid, t->cpu);
}
KOOPS_DEBUG("\n");
debug_stacktrace();
unlock_spin(&lock_time_check_lock);
debug_panic("deadlock in kernel: we can't go on together with suspicious minds");
}
#endif
}
exit_lock_gate:
/* release the gate so others can inspect it */
unlock_spin(&(gate->spinlock));
LOCK_DEBUG("[lock:%i] locked %p with %x\n", CPU_ID, gate, flags);
return err;
#endif
}
/* lock_gate_alloc
Allocate a readers-writer gate structure
=> ptr = pointer to word in which to store address of allocated gate
description = NULL-terminated human-readable label
<= 0 for success, or an error code (and ptr will be set to NULL)
*/
kresult lock_rw_gate_alloc(rw_gate **ptr, char *description)
{
kresult err;
rw_gate_pool *search = &gate_pool;
unsigned char slot_search_start, slot_search;
unsigned char slot_found = 0;
rw_gate *new_gate;
/* sanity check */
if(!ptr || !description) return e_bad_params;
if(vmm_nullbufferlen(description) >= LOCK_DESCRIPT_LENGTH)
return e_bad_params;
/* lock the locking code */
lock_gate(lock_lock, LOCK_WRITE);
/* try to find an existing pool with free slots */
while(search && search->nr_free == 0)
search = search->next;
/* if search is still NULL then grab a new page for the pool */
if(!search)
{
void *new_page;
err = vmm_req_phys_pg(&new_page, 1);
if(err)
{
unlock_gate(lock_lock, LOCK_WRITE);
return err; /* bail out if we're out of pages! */
}
/* allocate a new structure to describe this pool or give up */
err = vmm_malloc((void **)&search, sizeof(rw_gate_pool));
if(err)
{
unlock_gate(lock_lock, LOCK_WRITE);
return err; /* bail out if we're out of memory! */
}
/* initialise the pool structure and add to the head of
the linked list so it can be found quickly */
vmm_memset(search, 0, sizeof(rw_gate_pool));
search->nr_free = (unsigned char)LOCK_POOL_BITMAP_LENGTH_BITS;
search->physical_base = new_page;
search->virtual_base = KERNEL_PHYS2LOG(new_page);
vmm_memset(KERNEL_PHYS2LOG(new_page), 0, MEM_PGSIZE);
/* add us to the start of the list */
if(gate_pool.next)
{
search->next = gate_pool.next;
search->next->previous = search;
}
gate_pool.next = search;
search->previous = &gate_pool;
}
/* search is now valid or we wouldn't be here, so locate a free slot by
scanning through the bitmap, starting at the last known free slot */
slot_search = slot_search_start = search->last_free;
do
{
if(lock_bitmap_test(search->bitmap, slot_search) == 0)
slot_found = 1;
slot_search++;
if(slot_search >= LOCK_POOL_BITMAP_LENGTH_BITS)
slot_search = 0;
}
while(slot_search_start != slot_search && !slot_found);
/* set the bit and grab the address of the slot to use for the lock */
if(slot_found)
{
lock_bitmap_set(search->bitmap, slot_search);
/* initialise the gate structure */
new_gate = (rw_gate *)(unsigned int)search->virtual_base + (sizeof(rw_gate) * slot_search);
vmm_memset(new_gate, 0, (sizeof(rw_gate)));
*ptr = new_gate;
#ifdef DEBUG_LOCK_RWGATE_PROFILE
vmm_memcpy(&(new_gate->description), description, vmm_nullbufferlen(description) + sizeof('\0'));
#endif
/* update accounting, increment the next free slot but beware of
overflow */
search->nr_free--;
search->last_free++;
if(search->last_free >= LOCK_POOL_BITMAP_LENGTH_BITS)
slot_search = 0;
LOCK_DEBUG("[lock:%i] created new readers-writer lock '%s' %p (spinlock %p)\n",
description, new_gate, new_gate->spinlock);
unlock_gate(lock_lock, LOCK_WRITE);
return success;
}
/* something weird has happened if we've fallen this far, so
fall through to failure */
unlock_gate(lock_lock, LOCK_WRITE);
*ptr = NULL;
return e_failure;
}
