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

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

details:   https://anonhg.NetBSD.org/src/rev/29f99dbd12ef
branches:  trunk
changeset: 932242:29f99dbd12ef
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun May 03 01:25:48 2020 +0000

description:
Use cv_timedwaitclock_sig in futex.

Possible fix for hangs observed with Java under Linux emulation.

diffstat:

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

diffs (160 lines):

diff -r 7b14a56bb2ac -r 29f99dbd12ef sys/kern/sys_futex.c
--- a/sys/kern/sys_futex.c      Sun May 03 01:24:37 2020 +0000
+++ b/sys/kern/sys_futex.c      Sun May 03 01:25:48 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_futex.c,v 1.7 2020/04/28 17:27:03 riastradh Exp $  */
+/*     $NetBSD: sys_futex.c,v 1.8 2020/05/03 01:25:48 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 1.7 2020/04/28 17:27:03 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_futex.c,v 1.8 2020/05/03 01:25:48 riastradh Exp $");
 
 /*
  * Futexes
@@ -916,17 +916,18 @@
 }
 
 /*
- * futex_wait(fw, deadline, clkid)
+ * futex_wait(fw, timeout, clkid, clkflags)
  *
- *     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.
+ *     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.
  */
 static int
-futex_wait(struct futex_wait *fw, const struct timespec *deadline,
-    clockid_t clkid)
+futex_wait(struct futex_wait *fw, struct timespec *timeout, clockid_t clkid,
+    int clkflags)
 {
        int error = 0;
 
@@ -934,7 +935,7 @@
        mutex_enter(&fw->fw_lock);
 
        for (;;) {
-               /* If we're done yet, stop and report success.  */
+               /* If we're done already, stop and report success.  */
                if (fw->fw_bitset == 0 || fw->fw_futex == NULL) {
                        error = 0;
                        break;
@@ -945,30 +946,8 @@
                        break;
 
                /* Not done yet.  Wait.  */
-               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);
-               }
+               error = cv_timedwaitclock_sig(&fw->fw_cv, &fw->fw_lock,
+                   timeout, clkid, clkflags, DEFAULT_TIMEOUT_EPSILON);
        }
 
        /*
@@ -1188,13 +1167,11 @@
  */
 static int
 futex_func_wait(bool shared, int *uaddr, int val, int val3,
-    const struct timespec *timeout, clockid_t clkid, int clkflags,
+    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;
 
        /*
@@ -1208,17 +1185,6 @@
        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)
@@ -1255,7 +1221,7 @@
        f = NULL;
 
        /* Wait. */
-       error = futex_wait(fw, deadline, clkid);
+       error = futex_wait(fw, timeout, clkid, clkflags);
        if (error)
                goto out;
 
@@ -1580,8 +1546,8 @@
  *     parsed out.
  */
 int
-do_futex(int *uaddr, int op, int val, const struct timespec *timeout,
-    int *uaddr2, int val2, int val3, register_t *retval)
+do_futex(int *uaddr, int op, int val, 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 7b14a56bb2ac -r 29f99dbd12ef sys/sys/futex.h
--- a/sys/sys/futex.h   Sun May 03 01:24:37 2020 +0000
+++ b/sys/sys/futex.h   Sun May 03 01:25:48 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: futex.h,v 1.2 2020/04/27 02:54:42 rin Exp $    */
+/*     $NetBSD: futex.h,v 1.3 2020/05/03 01:25:48 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, const struct timespec *, int *, int,
-           int, register_t *);
+int    do_futex(int *, int, int, struct timespec *, int *, int, int,
+           register_t *);
 void   futex_sys_init(void);
 void   futex_sys_fini(void);
 #endif /* _KERNEL */