[src/trunk]: src/sys Revert "Use cv_timedwaitclock_sig in futex."

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/6e6aec743579
branches:  trunk
changeset: 971822:6e6aec743579
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue May 05 15:25:18 2020 +0000

description:
Revert "Use cv_timedwaitclock_sig in futex."

Turned out to break things; we'll do this another way.

diffstat:

 sys/kern/sys_futex.c |  70 ++++++++++++++++++++++++++++++++++++++-------------
 sys/sys/futex.h      |   6 ++--
 2 files changed, 55 insertions(+), 21 deletions(-)

diffs (160 lines):

diff -r 6eb5776bf409 -r 6e6aec743579 sys/kern/sys_futex.c
--- a/sys/kern/sys_futex.c      Tue May 05 15:23:32 2020 +0000
+++ b/sys/kern/sys_futex.c      Tue May 05 15:25:18 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_futex.c,v 1.10 2020/05/05 15:23:32 riastradh Exp $ */
+/*     $NetBSD: sys_futex.c,v 1.11 2020/05/05 15:25:18 riastradh Exp $ */
 
 /*-
  * Copyright (c) 2018, 2019, 2020 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_futex.c,v 1.10 2020/05/05 15:23:32 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_futex.c,v 1.11 2020/05/05 15:25:18 riastradh Exp $");
 
 /*
  * Futexes
@@ -916,18 +916,17 @@
 }
 
 /*
- * futex_wait(fw, timeout, clkid, clkflags)
+ * futex_wait(fw, deadline, clkid)
  *
- *     fw must be a waiter on a futex's queue.  Wait for timeout on
- *     the clock clkid according to clkflags (TIMER_*), or forever if
- *     timeout is NULL, for a futex wakeup.  Return 0 on explicit
- *     wakeup or destruction of futex, ETIMEDOUT on timeout,
- *     EINTR/ERESTART on signal.  Either way, fw will no longer be on
- *     a futex queue on return.
+ *     fw must be a waiter on a futex's queue.  Wait until deadline on
+ *     the clock clkid, or forever if deadline is NULL, for a futex
+ *     wakeup.  Return 0 on explicit wakeup or destruction of futex,
+ *     ETIMEDOUT on timeout, EINTR/ERESTART on signal.  Either way, fw
+ *     will no longer be on a futex queue on return.
  */
 static int
-futex_wait(struct futex_wait *fw, struct timespec *timeout, clockid_t clkid,
-    int clkflags)
+futex_wait(struct futex_wait *fw, const struct timespec *deadline,
+    clockid_t clkid)
 {
        int error = 0;
 
@@ -935,7 +934,7 @@
        mutex_enter(&fw->fw_lock);
 
        for (;;) {
-               /* If we're done already, stop and report success.  */
+               /* If we're done yet, stop and report success.  */
                if (fw->fw_bitset == 0 || fw->fw_futex == NULL) {
                        error = 0;
                        break;
@@ -946,8 +945,30 @@
                        break;
 
                /* Not done yet.  Wait.  */
-               error = cv_timedwaitclock_sig(&fw->fw_cv, &fw->fw_lock,
-                   timeout, clkid, clkflags, DEFAULT_TIMEOUT_EPSILON);
+               if (deadline) {
+                       struct timespec ts;
+
+                       /* Check our watch.  */
+                       error = clock_gettime1(clkid, &ts);
+                       if (error)
+                               break;
+
+                       /* If we're past the deadline, ETIMEDOUT.  */
+                       if (timespeccmp(deadline, &ts, <=)) {
+                               error = ETIMEDOUT;
+                               break;
+                       }
+
+                       /* Count how much time is left.  */
+                       timespecsub(deadline, &ts, &ts);
+
+                       /* Wait for that much time, allowing signals.  */
+                       error = cv_timedwait_sig(&fw->fw_cv, &fw->fw_lock,
+                           tstohz(&ts));
+               } else {
+                       /* Wait indefinitely, allowing signals. */
+                       error = cv_wait_sig(&fw->fw_cv, &fw->fw_lock);
+               }
        }
 
        /*
@@ -1167,11 +1188,13 @@
  */
 static int
 futex_func_wait(bool shared, int *uaddr, int val, int val3,
-    struct timespec *timeout, clockid_t clkid, int clkflags,
+    const struct timespec *timeout, clockid_t clkid, int clkflags,
     register_t *retval)
 {
        struct futex *f;
        struct futex_wait wait, *fw = &wait;
+       struct timespec ts;
+       const struct timespec *deadline;
        int error;
 
        /*
@@ -1185,6 +1208,17 @@
        if (!futex_test(uaddr, val))
                return EAGAIN;
 
+       /* Determine a deadline on the specified clock.  */
+       if (timeout == NULL || (clkflags & TIMER_ABSTIME) == TIMER_ABSTIME) {
+               deadline = timeout;
+       } else {
+               error = clock_gettime1(clkid, &ts);
+               if (error)
+                       return error;
+               timespecadd(&ts, timeout, &ts);
+               deadline = &ts;
+       }
+
        /* Get the futex, creating it if necessary.  */
        error = futex_lookup_create(uaddr, shared, &f);
        if (error)
@@ -1221,7 +1255,7 @@
        f = NULL;
 
        /* Wait. */
-       error = futex_wait(fw, timeout, clkid, clkflags);
+       error = futex_wait(fw, deadline, clkid);
        if (error)
                goto out;
 
@@ -1546,8 +1580,8 @@
  *     parsed out.
  */
 int
-do_futex(int *uaddr, int op, int val, struct timespec *timeout, int *uaddr2,
-    int val2, int val3, register_t *retval)
+do_futex(int *uaddr, int op, int val, const struct timespec *timeout,
+    int *uaddr2, int val2, int val3, register_t *retval)
 {
        const bool shared = (op & FUTEX_PRIVATE_FLAG) ? false : true;
        const clockid_t clkid = (op & FUTEX_CLOCK_REALTIME) ? CLOCK_REALTIME
diff -r 6eb5776bf409 -r 6e6aec743579 sys/sys/futex.h
--- a/sys/sys/futex.h   Tue May 05 15:23:32 2020 +0000
+++ b/sys/sys/futex.h   Tue May 05 15:25:18 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: futex.h,v 1.3 2020/05/03 01:25:48 riastradh Exp $      */
+/*     $NetBSD: futex.h,v 1.4 2020/05/05 15:25:18 riastradh Exp $      */
 
 /*-
  * Copyright (c) 2018, 2019 The NetBSD Foundation, Inc.
@@ -175,8 +175,8 @@
 
 int    futex_robust_head_lookup(struct lwp *, lwpid_t, void **);
 void   futex_release_all_lwp(struct lwp *, lwpid_t);
-int    do_futex(int *, int, int, struct timespec *, int *, int, int,
-           register_t *);
+int    do_futex(int *, int, int, const struct timespec *, int *, int,
+           int, register_t *);
 void   futex_sys_init(void);
 void   futex_sys_fini(void);
 #endif /* _KERNEL */