andre@0: /* This Source Code Form is subject to the terms of the Mozilla Public
andre@0: * License, v. 2.0. If a copy of the MPL was not distributed with this
andre@0: * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
andre@0:
andre@0: #include "nssrwlk.h"
andre@0: #include "nspr.h"
andre@0:
andre@0: PR_BEGIN_EXTERN_C
andre@0:
andre@0: /*
andre@0: * Reader-writer lock
andre@0: */
andre@0: struct nssRWLockStr {
andre@0: PZLock * rw_lock;
andre@0: char * rw_name; /* lock name */
andre@0: PRUint32 rw_rank; /* rank of the lock */
andre@0: PRInt32 rw_writer_locks; /* == 0, if unlocked */
andre@0: PRInt32 rw_reader_locks; /* == 0, if unlocked */
andre@0: /* > 0 , # of read locks */
andre@0: PRUint32 rw_waiting_readers; /* number of waiting readers */
andre@0: PRUint32 rw_waiting_writers; /* number of waiting writers */
andre@0: PZCondVar * rw_reader_waitq; /* cvar for readers */
andre@0: PZCondVar * rw_writer_waitq; /* cvar for writers */
andre@0: PRThread * rw_owner; /* lock owner for write-lock */
andre@0: /* Non-null if write lock held. */
andre@0: };
andre@0:
andre@0: PR_END_EXTERN_C
andre@0:
andre@0: #include <string.h>
andre@0:
andre@0: #ifdef DEBUG_RANK_ORDER
andre@0: #define NSS_RWLOCK_RANK_ORDER_DEBUG /* enable deadlock detection using
andre@0: rank-order for locks
andre@0: */
andre@0: #endif
andre@0:
andre@0: #ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
andre@0:
andre@0: static PRUintn nss_thread_rwlock_initialized;
andre@0: static PRUintn nss_thread_rwlock; /* TPD key for lock stack */
andre@0: static PRUintn nss_thread_rwlock_alloc_failed;
andre@0:
andre@0: #define _NSS_RWLOCK_RANK_ORDER_LIMIT 10
andre@0:
andre@0: typedef struct thread_rwlock_stack {
andre@0: PRInt32 trs_index; /* top of stack */
andre@0: NSSRWLock *trs_stack[_NSS_RWLOCK_RANK_ORDER_LIMIT]; /* stack of lock
andre@0: pointers */
andre@0: } thread_rwlock_stack;
andre@0:
andre@0: /* forward static declarations. */
andre@0: static PRUint32 nssRWLock_GetThreadRank(PRThread *me);
andre@0: static void nssRWLock_SetThreadRank(PRThread *me, NSSRWLock *rwlock);
andre@0: static void nssRWLock_UnsetThreadRank(PRThread *me, NSSRWLock *rwlock);
andre@0: static void nssRWLock_ReleaseLockStack(void *lock_stack);
andre@0:
andre@0: #endif
andre@0:
andre@0: #define UNTIL(x) while(!(x))
andre@0:
andre@0: /*
andre@0: * Reader/Writer Locks
andre@0: */
andre@0:
andre@0: /*
andre@0: * NSSRWLock_New
andre@0: * Create a reader-writer lock, with the given lock rank and lock name
andre@0: *
andre@0: */
andre@0:
andre@0: NSSRWLock *
andre@0: NSSRWLock_New(PRUint32 lock_rank, const char *lock_name)
andre@0: {
andre@0: NSSRWLock *rwlock;
andre@0:
andre@0: rwlock = PR_NEWZAP(NSSRWLock);
andre@0: if (rwlock == NULL)
andre@0: return NULL;
andre@0:
andre@0: rwlock->rw_lock = PZ_NewLock(nssILockRWLock);
andre@0: if (rwlock->rw_lock == NULL) {
andre@0: goto loser;
andre@0: }
andre@0: rwlock->rw_reader_waitq = PZ_NewCondVar(rwlock->rw_lock);
andre@0: if (rwlock->rw_reader_waitq == NULL) {
andre@0: goto loser;
andre@0: }
andre@0: rwlock->rw_writer_waitq = PZ_NewCondVar(rwlock->rw_lock);
andre@0: if (rwlock->rw_writer_waitq == NULL) {
andre@0: goto loser;
andre@0: }
andre@0: if (lock_name != NULL) {
andre@0: rwlock->rw_name = (char*) PR_Malloc(strlen(lock_name) + 1);
andre@0: if (rwlock->rw_name == NULL) {
andre@0: goto loser;
andre@0: }
andre@0: strcpy(rwlock->rw_name, lock_name);
andre@0: } else {
andre@0: rwlock->rw_name = NULL;
andre@0: }
andre@0: rwlock->rw_rank = lock_rank;
andre@0: rwlock->rw_waiting_readers = 0;
andre@0: rwlock->rw_waiting_writers = 0;
andre@0: rwlock->rw_reader_locks = 0;
andre@0: rwlock->rw_writer_locks = 0;
andre@0:
andre@0: return rwlock;
andre@0:
andre@0: loser:
andre@0: NSSRWLock_Destroy(rwlock);
andre@0: return(NULL);
andre@0: }
andre@0:
andre@0: /*
andre@0: ** Destroy the given RWLock "lock".
andre@0: */
andre@0: void
andre@0: NSSRWLock_Destroy(NSSRWLock *rwlock)
andre@0: {
andre@0: PR_ASSERT(rwlock != NULL);
andre@0: PR_ASSERT(rwlock->rw_waiting_readers == 0);
andre@0:
andre@0: /* XXX Shouldn't we lock the PZLock before destroying this?? */
andre@0:
andre@0: if (rwlock->rw_name)
andre@0: PR_Free(rwlock->rw_name);
andre@0: if (rwlock->rw_reader_waitq)
andre@0: PZ_DestroyCondVar(rwlock->rw_reader_waitq);
andre@0: if (rwlock->rw_writer_waitq)
andre@0: PZ_DestroyCondVar(rwlock->rw_writer_waitq);
andre@0: if (rwlock->rw_lock)
andre@0: PZ_DestroyLock(rwlock->rw_lock);
andre@0: PR_DELETE(rwlock);
andre@0: }
andre@0:
andre@0: /*
andre@0: ** Read-lock the RWLock.
andre@0: */
andre@0: void
andre@0: NSSRWLock_LockRead(NSSRWLock *rwlock)
andre@0: {
andre@0: PRThread *me = PR_GetCurrentThread();
andre@0:
andre@0: PZ_Lock(rwlock->rw_lock);
andre@0: #ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
andre@0:
andre@0: /*
andre@0: * assert that rank ordering is not violated; the rank of 'rwlock' should
andre@0: * be equal to or greater than the highest rank of all the locks held by
andre@0: * the thread.
andre@0: */
andre@0: PR_ASSERT((rwlock->rw_rank == NSS_RWLOCK_RANK_NONE) ||
andre@0: (rwlock->rw_rank >= nssRWLock_GetThreadRank(me)));
andre@0: #endif
andre@0: /*
andre@0: * wait if write-locked or if a writer is waiting; preference for writers
andre@0: */
andre@0: UNTIL ( (rwlock->rw_owner == me) || /* I own it, or */
andre@0: ((rwlock->rw_owner == NULL) && /* no-one owns it, and */
andre@0: (rwlock->rw_waiting_writers == 0))) { /* no-one is waiting to own */
andre@0:
andre@0: rwlock->rw_waiting_readers++;
andre@0: PZ_WaitCondVar(rwlock->rw_reader_waitq, PR_INTERVAL_NO_TIMEOUT);
andre@0: rwlock->rw_waiting_readers--;
andre@0: }
andre@0: rwlock->rw_reader_locks++; /* Increment read-lock count */
andre@0:
andre@0: PZ_Unlock(rwlock->rw_lock);
andre@0:
andre@0: #ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
andre@0: nssRWLock_SetThreadRank(me, rwlock);/* update thread's lock rank */
andre@0: #endif
andre@0: }
andre@0:
andre@0: /* Unlock a Read lock held on this RW lock.
andre@0: */
andre@0: void
andre@0: NSSRWLock_UnlockRead(NSSRWLock *rwlock)
andre@0: {
andre@0: PZ_Lock(rwlock->rw_lock);
andre@0:
andre@0: PR_ASSERT(rwlock->rw_reader_locks > 0); /* lock must be read locked */
andre@0:
andre@0: if (( rwlock->rw_reader_locks > 0) && /* caller isn't screwey */
andre@0: (--rwlock->rw_reader_locks == 0) && /* not read locked any more */
andre@0: ( rwlock->rw_owner == NULL) && /* not write locked */
andre@0: ( rwlock->rw_waiting_writers > 0)) { /* someone's waiting. */
andre@0:
andre@0: PZ_NotifyCondVar(rwlock->rw_writer_waitq); /* wake him up. */
andre@0: }
andre@0:
andre@0: PZ_Unlock(rwlock->rw_lock);
andre@0:
andre@0: #ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
andre@0: /*
andre@0: * update thread's lock rank
andre@0: */
andre@0: nssRWLock_UnsetThreadRank(me, rwlock);
andre@0: #endif
andre@0: return;
andre@0: }
andre@0:
andre@0: /*
andre@0: ** Write-lock the RWLock.
andre@0: */
andre@0: void
andre@0: NSSRWLock_LockWrite(NSSRWLock *rwlock)
andre@0: {
andre@0: PRThread *me = PR_GetCurrentThread();
andre@0:
andre@0: PZ_Lock(rwlock->rw_lock);
andre@0: #ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
andre@0: /*
andre@0: * assert that rank ordering is not violated; the rank of 'rwlock' should
andre@0: * be equal to or greater than the highest rank of all the locks held by
andre@0: * the thread.
andre@0: */
andre@0: PR_ASSERT((rwlock->rw_rank == NSS_RWLOCK_RANK_NONE) ||
andre@0: (rwlock->rw_rank >= nssRWLock_GetThreadRank(me)));
andre@0: #endif
andre@0: /*
andre@0: * wait if read locked or write locked.
andre@0: */
andre@0: PR_ASSERT(rwlock->rw_reader_locks >= 0);
andre@0: PR_ASSERT(me != NULL);
andre@0:
andre@0: UNTIL ( (rwlock->rw_owner == me) || /* I own write lock, or */
andre@0: ((rwlock->rw_owner == NULL) && /* no writer and */
andre@0: (rwlock->rw_reader_locks == 0))) { /* no readers, either. */
andre@0:
andre@0: rwlock->rw_waiting_writers++;
andre@0: PZ_WaitCondVar(rwlock->rw_writer_waitq, PR_INTERVAL_NO_TIMEOUT);
andre@0: rwlock->rw_waiting_writers--;
andre@0: PR_ASSERT(rwlock->rw_reader_locks >= 0);
andre@0: }
andre@0:
andre@0: PR_ASSERT(rwlock->rw_reader_locks == 0);
andre@0: /*
andre@0: * apply write lock
andre@0: */
andre@0: rwlock->rw_owner = me;
andre@0: rwlock->rw_writer_locks++; /* Increment write-lock count */
andre@0:
andre@0: PZ_Unlock(rwlock->rw_lock);
andre@0:
andre@0: #ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
andre@0: /*
andre@0: * update thread's lock rank
andre@0: */
andre@0: nssRWLock_SetThreadRank(me,rwlock);
andre@0: #endif
andre@0: }
andre@0:
andre@0: /* Unlock a Read lock held on this RW lock.
andre@0: */
andre@0: void
andre@0: NSSRWLock_UnlockWrite(NSSRWLock *rwlock)
andre@0: {
andre@0: PRThread *me = PR_GetCurrentThread();
andre@0:
andre@0: PZ_Lock(rwlock->rw_lock);
andre@0: PR_ASSERT(rwlock->rw_owner == me); /* lock must be write-locked by me. */
andre@0: PR_ASSERT(rwlock->rw_writer_locks > 0); /* lock must be write locked */
andre@0:
andre@0: if ( rwlock->rw_owner == me && /* I own it, and */
andre@0: rwlock->rw_writer_locks > 0 && /* I own it, and */
andre@0: --rwlock->rw_writer_locks == 0) { /* I'm all done with it */
andre@0:
andre@0: rwlock->rw_owner = NULL; /* I don't own it any more. */
andre@0:
andre@0: /* Give preference to waiting writers. */
andre@0: if (rwlock->rw_waiting_writers > 0) {
andre@0: if (rwlock->rw_reader_locks == 0)
andre@0: PZ_NotifyCondVar(rwlock->rw_writer_waitq);
andre@0: } else if (rwlock->rw_waiting_readers > 0) {
andre@0: PZ_NotifyAllCondVar(rwlock->rw_reader_waitq);
andre@0: }
andre@0: }
andre@0: PZ_Unlock(rwlock->rw_lock);
andre@0:
andre@0: #ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
andre@0: /*
andre@0: * update thread's lock rank
andre@0: */
andre@0: nssRWLock_UnsetThreadRank(me, rwlock);
andre@0: #endif
andre@0: return;
andre@0: }
andre@0:
andre@0: /* This is primarily for debugging, i.e. for inclusion in ASSERT calls. */
andre@0: PRBool
andre@0: NSSRWLock_HaveWriteLock(NSSRWLock *rwlock) {
andre@0: PRBool ownWriteLock;
andre@0: PRThread *me = PR_GetCurrentThread();
andre@0:
andre@0: /* This lock call isn't really necessary.
andre@0: ** If this thread is the owner, that fact cannot change during this call,
andre@0: ** because this thread is in this call.
andre@0: ** If this thread is NOT the owner, the owner could change, but it
andre@0: ** could not become this thread.
andre@0: */
andre@0: #if UNNECESSARY
andre@0: PZ_Lock(rwlock->rw_lock);
andre@0: #endif
andre@0: ownWriteLock = (PRBool)(me == rwlock->rw_owner);
andre@0: #if UNNECESSARY
andre@0: PZ_Unlock(rwlock->rw_lock);
andre@0: #endif
andre@0: return ownWriteLock;
andre@0: }
andre@0:
andre@0: #ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
andre@0:
andre@0: /*
andre@0: * nssRWLock_SetThreadRank
andre@0: * Set a thread's lock rank, which is the highest of the ranks of all
andre@0: * the locks held by the thread. Pointers to the locks are added to a
andre@0: * per-thread list, which is anchored off a thread-private data key.
andre@0: */
andre@0:
andre@0: static void
andre@0: nssRWLock_SetThreadRank(PRThread *me, NSSRWLock *rwlock)
andre@0: {
andre@0: thread_rwlock_stack *lock_stack;
andre@0: PRStatus rv;
andre@0:
andre@0: /*
andre@0: * allocated thread-private-data for rwlock list, if not already allocated
andre@0: */
andre@0: if (!nss_thread_rwlock_initialized) {
andre@0: /*
andre@0: * allocate tpd, only if not failed already
andre@0: */
andre@0: if (!nss_thread_rwlock_alloc_failed) {
andre@0: if (PR_NewThreadPrivateIndex(&nss_thread_rwlock,
andre@0: nssRWLock_ReleaseLockStack)
andre@0: == PR_FAILURE) {
andre@0: nss_thread_rwlock_alloc_failed = 1;
andre@0: return;
andre@0: }
andre@0: } else
andre@0: return;
andre@0: }
andre@0: /*
andre@0: * allocate a lock stack
andre@0: */
andre@0: if ((lock_stack = PR_GetThreadPrivate(nss_thread_rwlock)) == NULL) {
andre@0: lock_stack = (thread_rwlock_stack *)
andre@0: PR_CALLOC(1 * sizeof(thread_rwlock_stack));
andre@0: if (lock_stack) {
andre@0: rv = PR_SetThreadPrivate(nss_thread_rwlock, lock_stack);
andre@0: if (rv == PR_FAILURE) {
andre@0: PR_DELETE(lock_stack);
andre@0: nss_thread_rwlock_alloc_failed = 1;
andre@0: return;
andre@0: }
andre@0: } else {
andre@0: nss_thread_rwlock_alloc_failed = 1;
andre@0: return;
andre@0: }
andre@0: }
andre@0: /*
andre@0: * add rwlock to lock stack, if limit is not exceeded
andre@0: */
andre@0: if (lock_stack) {
andre@0: if (lock_stack->trs_index < _NSS_RWLOCK_RANK_ORDER_LIMIT)
andre@0: lock_stack->trs_stack[lock_stack->trs_index++] = rwlock;
andre@0: }
andre@0: nss_thread_rwlock_initialized = 1;
andre@0: }
andre@0:
andre@0: static void
andre@0: nssRWLock_ReleaseLockStack(void *lock_stack)
andre@0: {
andre@0: PR_ASSERT(lock_stack);
andre@0: PR_DELETE(lock_stack);
andre@0: }
andre@0:
andre@0: /*
andre@0: * nssRWLock_GetThreadRank
andre@0: *
andre@0: * return thread's lock rank. If thread-private-data for the lock
andre@0: * stack is not allocated, return NSS_RWLOCK_RANK_NONE.
andre@0: */
andre@0:
andre@0: static PRUint32
andre@0: nssRWLock_GetThreadRank(PRThread *me)
andre@0: {
andre@0: thread_rwlock_stack *lock_stack;
andre@0:
andre@0: if (nss_thread_rwlock_initialized) {
andre@0: if ((lock_stack = PR_GetThreadPrivate(nss_thread_rwlock)) == NULL)
andre@0: return (NSS_RWLOCK_RANK_NONE);
andre@0: else
andre@0: return(lock_stack->trs_stack[lock_stack->trs_index - 1]->rw_rank);
andre@0:
andre@0: } else
andre@0: return (NSS_RWLOCK_RANK_NONE);
andre@0: }
andre@0:
andre@0: /*
andre@0: * nssRWLock_UnsetThreadRank
andre@0: *
andre@0: * remove the rwlock from the lock stack. Since locks may not be
andre@0: * unlocked in a FIFO order, the entire lock stack is searched.
andre@0: */
andre@0:
andre@0: static void
andre@0: nssRWLock_UnsetThreadRank(PRThread *me, NSSRWLock *rwlock)
andre@0: {
andre@0: thread_rwlock_stack *lock_stack;
andre@0: int new_index = 0, index, done = 0;
andre@0:
andre@0: if (!nss_thread_rwlock_initialized)
andre@0: return;
andre@0:
andre@0: lock_stack = PR_GetThreadPrivate(nss_thread_rwlock);
andre@0:
andre@0: PR_ASSERT(lock_stack != NULL);
andre@0:
andre@0: index = lock_stack->trs_index - 1;
andre@0: while (index-- >= 0) {
andre@0: if ((lock_stack->trs_stack[index] == rwlock) && !done) {
andre@0: /*
andre@0: * reset the slot for rwlock
andre@0: */
andre@0: lock_stack->trs_stack[index] = NULL;
andre@0: done = 1;
andre@0: }
andre@0: /*
andre@0: * search for the lowest-numbered empty slot, above which there are
andre@0: * no non-empty slots
andre@0: */
andre@0: if ((lock_stack->trs_stack[index] != NULL) && !new_index)
andre@0: new_index = index + 1;
andre@0: if (done && new_index)
andre@0: break;
andre@0: }
andre@0: /*
andre@0: * set top of stack to highest numbered empty slot
andre@0: */
andre@0: lock_stack->trs_index = new_index;
andre@0:
andre@0: }
andre@0:
andre@0: #endif /* NSS_RWLOCK_RANK_ORDER_DEBUG */