diff options
Diffstat (limited to 'pr/include/md/_pth.h')
| -rw-r--r-- | pr/include/md/_pth.h | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/pr/include/md/_pth.h b/pr/include/md/_pth.h index 997f32f7..be65ab74 100644 --- a/pr/include/md/_pth.h +++ b/pr/include/md/_pth.h @@ -96,6 +96,52 @@ #define _PT_PTHREAD_COND_INIT(m, a) pthread_cond_init(&(m), &(a)) #endif +/* The pthreads standard does not specify an invalid value for the + * pthread_t handle. (0 is usually an invalid pthread identifier + * but there are exceptions, for example, DG/UX.) These macros + * define a way to set the handle to or compare the handle with an + * invalid identifier. These macros are not portable and may be + * more of a problem as we adapt to more pthreads implementations. + * They are only used in the PRMonitor functions. Do not use them + * in new code. + * + * Unfortunately some of our clients depend on certain properties + * of our PRMonitor implementation, preventing us from replacing + * it by a portable implementation. + * - High-performance servers like the fact that PR_EnterMonitor + * only calls PR_Lock and PR_ExitMonitor only calls PR_Unlock. + * (A portable implementation would use a PRLock and a PRCondVar + * to implement the recursive lock in a monitor and call both + * PR_Lock and PR_Unlock in PR_EnterMonitor and PR_ExitMonitor.) + * Unfortunately this forces us to read the monitor owner field + * without holding a lock. + * - One way to make it safe to read the monitor owner field + * without holding a lock is to make that field a PRThread* + * (one should be able to read a pointer with a single machine + * instruction). However, PR_GetCurrentThread calls calloc if + * it is called by a thread that was not created by NSPR. The + * malloc tracing tools in the Mozilla client use PRMonitor for + * locking in their malloc, calloc, and free functions. If + * PR_EnterMonitor calls any of these functions, infinite + * recursion ensues. + */ +#if defined(_PR_DCETHREADS) +#define _PT_PTHREAD_INVALIDATE_THR_HANDLE(t) \ + memset(&(t), 0, sizeof(pthread_t)) +#define _PT_PTHREAD_THR_HANDLE_IS_INVALID(t) \ + (!memcmp(&(t), &pt_zero_tid, sizeof(pthread_t))) +#define _PT_PTHREAD_COPY_THR_HANDLE(st, dt) (dt) = (st) +#elif defined(IRIX) || defined(OSF1) || defined(AIX) || defined(SOLARIS) \ + || defined(HPUX) || defined(LINUX) || defined(FREEBSD) \ + || defined(NETBSD) || defined(OPENBSD) || defined(BSDI) \ + || defined(VMS) || defined(NTO) || defined(RHAPSODY) +#define _PT_PTHREAD_INVALIDATE_THR_HANDLE(t) (t) = 0 +#define _PT_PTHREAD_THR_HANDLE_IS_INVALID(t) (t) == 0 +#define _PT_PTHREAD_COPY_THR_HANDLE(st, dt) (dt) = (st) +#else +#error "pthreads is not supported for this architecture" +#endif + #if defined(_PR_DCETHREADS) #define _PT_PTHREAD_ATTR_INIT pthread_attr_create #define _PT_PTHREAD_ATTR_DESTROY pthread_attr_delete |