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-rw-r--r--security/nss/lib/util/nssrwlk.c448
1 files changed, 448 insertions, 0 deletions
diff --git a/security/nss/lib/util/nssrwlk.c b/security/nss/lib/util/nssrwlk.c
new file mode 100644
index 000000000..dbaeca24b
--- /dev/null
+++ b/security/nss/lib/util/nssrwlk.c
@@ -0,0 +1,448 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nssrwlk.h"
+#include "nspr.h"
+
+PR_BEGIN_EXTERN_C
+
+/*
+ * Reader-writer lock
+ */
+struct nssRWLockStr {
+ PZLock *rw_lock;
+ char *rw_name; /* lock name */
+ PRUint32 rw_rank; /* rank of the lock */
+ PRInt32 rw_writer_locks; /* == 0, if unlocked */
+ PRInt32 rw_reader_locks; /* == 0, if unlocked */
+ /* > 0 , # of read locks */
+ PRUint32 rw_waiting_readers; /* number of waiting readers */
+ PRUint32 rw_waiting_writers; /* number of waiting writers */
+ PZCondVar *rw_reader_waitq; /* cvar for readers */
+ PZCondVar *rw_writer_waitq; /* cvar for writers */
+ PRThread *rw_owner; /* lock owner for write-lock */
+ /* Non-null if write lock held. */
+};
+
+PR_END_EXTERN_C
+
+#include <string.h>
+
+#ifdef DEBUG_RANK_ORDER
+#define NSS_RWLOCK_RANK_ORDER_DEBUG /* enable deadlock detection using \
+ rank-order for locks \
+ */
+#endif
+
+#ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
+
+static PRUintn nss_thread_rwlock_initialized;
+static PRUintn nss_thread_rwlock; /* TPD key for lock stack */
+static PRUintn nss_thread_rwlock_alloc_failed;
+
+#define _NSS_RWLOCK_RANK_ORDER_LIMIT 10
+
+typedef struct thread_rwlock_stack {
+ PRInt32 trs_index; /* top of stack */
+ NSSRWLock *trs_stack[_NSS_RWLOCK_RANK_ORDER_LIMIT]; /* stack of lock
+ pointers */
+} thread_rwlock_stack;
+
+/* forward static declarations. */
+static PRUint32 nssRWLock_GetThreadRank(PRThread *me);
+static void nssRWLock_SetThreadRank(PRThread *me, NSSRWLock *rwlock);
+static void nssRWLock_UnsetThreadRank(PRThread *me, NSSRWLock *rwlock);
+static void nssRWLock_ReleaseLockStack(void *lock_stack);
+
+#endif
+
+#define UNTIL(x) while (!(x))
+
+/*
+ * Reader/Writer Locks
+ */
+
+/*
+ * NSSRWLock_New
+ * Create a reader-writer lock, with the given lock rank and lock name
+ *
+ */
+
+NSSRWLock *
+NSSRWLock_New(PRUint32 lock_rank, const char *lock_name)
+{
+ NSSRWLock *rwlock;
+
+ rwlock = PR_NEWZAP(NSSRWLock);
+ if (rwlock == NULL)
+ return NULL;
+
+ rwlock->rw_lock = PZ_NewLock(nssILockRWLock);
+ if (rwlock->rw_lock == NULL) {
+ goto loser;
+ }
+ rwlock->rw_reader_waitq = PZ_NewCondVar(rwlock->rw_lock);
+ if (rwlock->rw_reader_waitq == NULL) {
+ goto loser;
+ }
+ rwlock->rw_writer_waitq = PZ_NewCondVar(rwlock->rw_lock);
+ if (rwlock->rw_writer_waitq == NULL) {
+ goto loser;
+ }
+ if (lock_name != NULL) {
+ rwlock->rw_name = (char *)PR_Malloc((PRUint32)strlen(lock_name) + 1);
+ if (rwlock->rw_name == NULL) {
+ goto loser;
+ }
+ strcpy(rwlock->rw_name, lock_name);
+ } else {
+ rwlock->rw_name = NULL;
+ }
+ rwlock->rw_rank = lock_rank;
+ rwlock->rw_waiting_readers = 0;
+ rwlock->rw_waiting_writers = 0;
+ rwlock->rw_reader_locks = 0;
+ rwlock->rw_writer_locks = 0;
+
+ return rwlock;
+
+loser:
+ NSSRWLock_Destroy(rwlock);
+ return (NULL);
+}
+
+/*
+** Destroy the given RWLock "lock".
+*/
+void
+NSSRWLock_Destroy(NSSRWLock *rwlock)
+{
+ PR_ASSERT(rwlock != NULL);
+ PR_ASSERT(rwlock->rw_waiting_readers == 0);
+
+ /* XXX Shouldn't we lock the PZLock before destroying this?? */
+
+ if (rwlock->rw_name)
+ PR_Free(rwlock->rw_name);
+ if (rwlock->rw_reader_waitq)
+ PZ_DestroyCondVar(rwlock->rw_reader_waitq);
+ if (rwlock->rw_writer_waitq)
+ PZ_DestroyCondVar(rwlock->rw_writer_waitq);
+ if (rwlock->rw_lock)
+ PZ_DestroyLock(rwlock->rw_lock);
+ PR_DELETE(rwlock);
+}
+
+/*
+** Read-lock the RWLock.
+*/
+void
+NSSRWLock_LockRead(NSSRWLock *rwlock)
+{
+ PRThread *me = PR_GetCurrentThread();
+
+ PZ_Lock(rwlock->rw_lock);
+#ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
+
+ /*
+ * assert that rank ordering is not violated; the rank of 'rwlock' should
+ * be equal to or greater than the highest rank of all the locks held by
+ * the thread.
+ */
+ PR_ASSERT((rwlock->rw_rank == NSS_RWLOCK_RANK_NONE) ||
+ (rwlock->rw_rank >= nssRWLock_GetThreadRank(me)));
+#endif
+ /*
+ * wait if write-locked or if a writer is waiting; preference for writers
+ */
+ UNTIL((rwlock->rw_owner == me) || /* I own it, or */
+ ((rwlock->rw_owner == NULL) && /* no-one owns it, and */
+ (rwlock->rw_waiting_writers == 0)))
+ { /* no-one is waiting to own */
+
+ rwlock->rw_waiting_readers++;
+ PZ_WaitCondVar(rwlock->rw_reader_waitq, PR_INTERVAL_NO_TIMEOUT);
+ rwlock->rw_waiting_readers--;
+ }
+ rwlock->rw_reader_locks++; /* Increment read-lock count */
+
+ PZ_Unlock(rwlock->rw_lock);
+
+#ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
+ nssRWLock_SetThreadRank(me, rwlock); /* update thread's lock rank */
+#endif
+}
+
+/* Unlock a Read lock held on this RW lock.
+*/
+void
+NSSRWLock_UnlockRead(NSSRWLock *rwlock)
+{
+ PZ_Lock(rwlock->rw_lock);
+
+ PR_ASSERT(rwlock->rw_reader_locks > 0); /* lock must be read locked */
+
+ if ((rwlock->rw_reader_locks > 0) && /* caller isn't screwey */
+ (--rwlock->rw_reader_locks == 0) && /* not read locked any more */
+ (rwlock->rw_owner == NULL) && /* not write locked */
+ (rwlock->rw_waiting_writers > 0)) { /* someone's waiting. */
+
+ PZ_NotifyCondVar(rwlock->rw_writer_waitq); /* wake him up. */
+ }
+
+ PZ_Unlock(rwlock->rw_lock);
+
+#ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
+ /*
+ * update thread's lock rank
+ */
+ nssRWLock_UnsetThreadRank(me, rwlock);
+#endif
+ return;
+}
+
+/*
+** Write-lock the RWLock.
+*/
+void
+NSSRWLock_LockWrite(NSSRWLock *rwlock)
+{
+ PRThread *me = PR_GetCurrentThread();
+
+ PZ_Lock(rwlock->rw_lock);
+#ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
+ /*
+ * assert that rank ordering is not violated; the rank of 'rwlock' should
+ * be equal to or greater than the highest rank of all the locks held by
+ * the thread.
+ */
+ PR_ASSERT((rwlock->rw_rank == NSS_RWLOCK_RANK_NONE) ||
+ (rwlock->rw_rank >= nssRWLock_GetThreadRank(me)));
+#endif
+ /*
+ * wait if read locked or write locked.
+ */
+ PR_ASSERT(rwlock->rw_reader_locks >= 0);
+ PR_ASSERT(me != NULL);
+
+ UNTIL((rwlock->rw_owner == me) || /* I own write lock, or */
+ ((rwlock->rw_owner == NULL) && /* no writer and */
+ (rwlock->rw_reader_locks == 0)))
+ { /* no readers, either. */
+
+ rwlock->rw_waiting_writers++;
+ PZ_WaitCondVar(rwlock->rw_writer_waitq, PR_INTERVAL_NO_TIMEOUT);
+ rwlock->rw_waiting_writers--;
+ PR_ASSERT(rwlock->rw_reader_locks >= 0);
+ }
+
+ PR_ASSERT(rwlock->rw_reader_locks == 0);
+ /*
+ * apply write lock
+ */
+ rwlock->rw_owner = me;
+ rwlock->rw_writer_locks++; /* Increment write-lock count */
+
+ PZ_Unlock(rwlock->rw_lock);
+
+#ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
+ /*
+ * update thread's lock rank
+ */
+ nssRWLock_SetThreadRank(me, rwlock);
+#endif
+}
+
+/* Unlock a Read lock held on this RW lock.
+*/
+void
+NSSRWLock_UnlockWrite(NSSRWLock *rwlock)
+{
+ PRThread *me = PR_GetCurrentThread();
+
+ PZ_Lock(rwlock->rw_lock);
+ PR_ASSERT(rwlock->rw_owner == me); /* lock must be write-locked by me. */
+ PR_ASSERT(rwlock->rw_writer_locks > 0); /* lock must be write locked */
+
+ if (rwlock->rw_owner == me && /* I own it, and */
+ rwlock->rw_writer_locks > 0 && /* I own it, and */
+ --rwlock->rw_writer_locks == 0) { /* I'm all done with it */
+
+ rwlock->rw_owner = NULL; /* I don't own it any more. */
+
+ /* Give preference to waiting writers. */
+ if (rwlock->rw_waiting_writers > 0) {
+ if (rwlock->rw_reader_locks == 0)
+ PZ_NotifyCondVar(rwlock->rw_writer_waitq);
+ } else if (rwlock->rw_waiting_readers > 0) {
+ PZ_NotifyAllCondVar(rwlock->rw_reader_waitq);
+ }
+ }
+ PZ_Unlock(rwlock->rw_lock);
+
+#ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
+ /*
+ * update thread's lock rank
+ */
+ nssRWLock_UnsetThreadRank(me, rwlock);
+#endif
+ return;
+}
+
+/* This is primarily for debugging, i.e. for inclusion in ASSERT calls. */
+PRBool
+NSSRWLock_HaveWriteLock(NSSRWLock *rwlock)
+{
+ PRBool ownWriteLock;
+ PRThread *me = PR_GetCurrentThread();
+
+/* This lock call isn't really necessary.
+ ** If this thread is the owner, that fact cannot change during this call,
+ ** because this thread is in this call.
+ ** If this thread is NOT the owner, the owner could change, but it
+ ** could not become this thread.
+ */
+#if UNNECESSARY
+ PZ_Lock(rwlock->rw_lock);
+#endif
+ ownWriteLock = (PRBool)(me == rwlock->rw_owner);
+#if UNNECESSARY
+ PZ_Unlock(rwlock->rw_lock);
+#endif
+ return ownWriteLock;
+}
+
+#ifdef NSS_RWLOCK_RANK_ORDER_DEBUG
+
+/*
+ * nssRWLock_SetThreadRank
+ * Set a thread's lock rank, which is the highest of the ranks of all
+ * the locks held by the thread. Pointers to the locks are added to a
+ * per-thread list, which is anchored off a thread-private data key.
+ */
+
+static void
+nssRWLock_SetThreadRank(PRThread *me, NSSRWLock *rwlock)
+{
+ thread_rwlock_stack *lock_stack;
+ PRStatus rv;
+
+ /*
+ * allocated thread-private-data for rwlock list, if not already allocated
+ */
+ if (!nss_thread_rwlock_initialized) {
+ /*
+ * allocate tpd, only if not failed already
+ */
+ if (!nss_thread_rwlock_alloc_failed) {
+ if (PR_NewThreadPrivateIndex(&nss_thread_rwlock,
+ nssRWLock_ReleaseLockStack) == PR_FAILURE) {
+ nss_thread_rwlock_alloc_failed = 1;
+ return;
+ }
+ } else
+ return;
+ }
+ /*
+ * allocate a lock stack
+ */
+ if ((lock_stack = PR_GetThreadPrivate(nss_thread_rwlock)) == NULL) {
+ lock_stack = (thread_rwlock_stack *)
+ PR_CALLOC(1 * sizeof(thread_rwlock_stack));
+ if (lock_stack) {
+ rv = PR_SetThreadPrivate(nss_thread_rwlock, lock_stack);
+ if (rv == PR_FAILURE) {
+ PR_DELETE(lock_stack);
+ nss_thread_rwlock_alloc_failed = 1;
+ return;
+ }
+ } else {
+ nss_thread_rwlock_alloc_failed = 1;
+ return;
+ }
+ }
+ /*
+ * add rwlock to lock stack, if limit is not exceeded
+ */
+ if (lock_stack) {
+ if (lock_stack->trs_index < _NSS_RWLOCK_RANK_ORDER_LIMIT)
+ lock_stack->trs_stack[lock_stack->trs_index++] = rwlock;
+ }
+ nss_thread_rwlock_initialized = 1;
+}
+
+static void
+nssRWLock_ReleaseLockStack(void *lock_stack)
+{
+ PR_ASSERT(lock_stack);
+ PR_DELETE(lock_stack);
+}
+
+/*
+ * nssRWLock_GetThreadRank
+ *
+ * return thread's lock rank. If thread-private-data for the lock
+ * stack is not allocated, return NSS_RWLOCK_RANK_NONE.
+ */
+
+static PRUint32
+nssRWLock_GetThreadRank(PRThread *me)
+{
+ thread_rwlock_stack *lock_stack;
+
+ if (nss_thread_rwlock_initialized) {
+ if ((lock_stack = PR_GetThreadPrivate(nss_thread_rwlock)) == NULL)
+ return (NSS_RWLOCK_RANK_NONE);
+ else
+ return (lock_stack->trs_stack[lock_stack->trs_index - 1]->rw_rank);
+
+ } else
+ return (NSS_RWLOCK_RANK_NONE);
+}
+
+/*
+ * nssRWLock_UnsetThreadRank
+ *
+ * remove the rwlock from the lock stack. Since locks may not be
+ * unlocked in a FIFO order, the entire lock stack is searched.
+ */
+
+static void
+nssRWLock_UnsetThreadRank(PRThread *me, NSSRWLock *rwlock)
+{
+ thread_rwlock_stack *lock_stack;
+ int new_index = 0, index, done = 0;
+
+ if (!nss_thread_rwlock_initialized)
+ return;
+
+ lock_stack = PR_GetThreadPrivate(nss_thread_rwlock);
+
+ PR_ASSERT(lock_stack != NULL);
+
+ index = lock_stack->trs_index - 1;
+ while (index-- >= 0) {
+ if ((lock_stack->trs_stack[index] == rwlock) && !done) {
+ /*
+ * reset the slot for rwlock
+ */
+ lock_stack->trs_stack[index] = NULL;
+ done = 1;
+ }
+ /*
+ * search for the lowest-numbered empty slot, above which there are
+ * no non-empty slots
+ */
+ if ((lock_stack->trs_stack[index] != NULL) && !new_index)
+ new_index = index + 1;
+ if (done && new_index)
+ break;
+ }
+ /*
+ * set top of stack to highest numbered empty slot
+ */
+ lock_stack->trs_index = new_index;
+}
+
+#endif /* NSS_RWLOCK_RANK_ORDER_DEBUG */