document pthread structure ABI constraints in comments

[musl] / src / internal / pthread_impl.h

diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h
index ae0ab1c..f6a4f2c 100644 (file)
--- a/src/internal/pthread_impl.h
+++ b/src/internal/pthread_impl.h
@@ -13,11 +13,15 @@
 #define pthread __pthread
 
 struct pthread {
+       /* Part 1 -- these fields may be external or
+        * internal (accessed via asm) ABI. Do not change. */
        struct pthread *self;
        void **dtv, *unused1, *unused2;
        uintptr_t sysinfo;
        uintptr_t canary, canary2;
        pid_t tid, pid;
+
+       /* Part 2 -- implementation details, non-ABI. */
        int tsd_used, errno_val;
        volatile int cancel, canceldisable, cancelasync;
        int detached;
@@ -39,13 +43,17 @@ struct pthread {
        int unblock_cancel;
        volatile int timer_id;
        locale_t locale;
-       volatile int killlock[2];
-       volatile int exitlock[2];
+       volatile int killlock[1];
+       volatile int exitlock[1];
        volatile int startlock[2];
        unsigned long sigmask[_NSIG/8/sizeof(long)];
        char *dlerror_buf;
        int dlerror_flag;
        void *stdio_locks;
+       size_t guard_size;
+
+       /* Part 3 -- the positions of these fields relative to
+        * the end of the structure is external and internal ABI. */
        uintptr_t canary_at_end;
        void **dtv_copy;
 };
@@ -131,11 +139,17 @@ int __timedwait_cp(volatile int *, int, clockid_t, const struct timespec *, int)
 void __wait(volatile int *, volatile int *, int, int);
 static inline void __wake(volatile void *addr, int cnt, int priv)
 {
-       if (priv) priv = 128;
+       if (priv) priv = FUTEX_PRIVATE;
        if (cnt<0) cnt = INT_MAX;
        __syscall(SYS_futex, addr, FUTEX_WAKE|priv, cnt) != -ENOSYS ||
        __syscall(SYS_futex, addr, FUTEX_WAKE, cnt);
 }
+static inline void __futexwait(volatile void *addr, int val, int priv)
+{
+       if (priv) priv = FUTEX_PRIVATE;
+       __syscall(SYS_futex, addr, FUTEX_WAIT|priv, val) != -ENOSYS ||
+       __syscall(SYS_futex, addr, FUTEX_WAIT, val);
+}
 
 void __acquire_ptc(void);
 void __release_ptc(void);