nptl: Replace non cancellable pause/nanosleep with futex

To help y2038 work avoid duplicate all the logic of nanosleep on
non cancellable version, the patch replace it with a new futex
operation, lll_timedwait.  The changes are:

  - Add a expected value for __lll_clocklock_wait, so it can be used
    to wait for generic values.

  - Remove its internal atomic operation and move the logic to
    __lll_clocklock.  It makes __lll_clocklock_wait even more generic
    and __lll_clocklock slight faster on fast-path (since it won't
    require a function call anymore).

  - Add lll_timedwait, which uses __lll_clocklock_wait, to replace both
    __pause_nocancel and __nanosleep_nocancel.

It also allows remove the sparc32 __lll_clocklock_wait implementation
(since it is similar to the generic one).

Checked on x86_64-linux-gnu, sparcv9-linux-gnu, and i686-linux-gnu.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

nptl/lll_timedlock_wait.c

@@ -25,39 +25,38 @@
 
 
 int
-__lll_clocklock_wait (int *futex, clockid_t clockid,
+__lll_clocklock_wait (int *futex, int val, clockid_t clockid,
 		      const struct timespec *abstime, int private)
 {
-  /* Reject invalid timeouts.  */
+  struct timespec ts, *tsp = NULL;
-  if (! valid_nanoseconds (abstime->tv_nsec))
-    return EINVAL;
 
-  /* Try locking.  */
+  if (abstime != NULL)
-  while (atomic_exchange_acq (futex, 2) != 0)
     {
-      struct timespec ts;
+      /* Reject invalid timeouts.  */
+      if (! valid_nanoseconds (abstime->tv_nsec))
+        return EINVAL;
 
-      /* Get the current time. This can only fail if clockid is not
+      /* Get the current time. This can only fail if clockid is not valid.  */
-         valid.  */
       if (__glibc_unlikely (__clock_gettime (clockid, &ts) != 0))
         return EINVAL;
 
       /* Compute relative timeout.  */
-      struct timespec rt;
+      ts.tv_sec = abstime->tv_sec - ts.tv_sec;
-      rt.tv_sec = abstime->tv_sec - ts.tv_sec;
+      ts.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
-      rt.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
+      if (ts.tv_nsec < 0)
-      if (rt.tv_nsec < 0)
         {
-          rt.tv_nsec += 1000000000;
+	  ts.tv_nsec += 1000000000;
-          --rt.tv_sec;
+	  --ts.tv_sec;
         }
 
-      if (rt.tv_sec < 0)
+      if (ts.tv_sec < 0)
         return ETIMEDOUT;
 
-      /* If *futex == 2, wait until woken or timeout.  */
+      tsp = &ts;
-      lll_futex_timed_wait (futex, 2, &rt, private);
     }
 
+  /* If *futex == val, wait until woken or timeout.  */
+  lll_futex_timed_wait (futex, val, tsp, private);
+
   return 0;
 }

nptl/pthread_mutex_lock.c

@@ -434,7 +434,8 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex)
 
 		/* Delay the thread indefinitely.  */
 		while (1)
-		  __pause_nocancel ();
+		  lll_timedwait (&(int){0}, 0, 0 /* ignored */, NULL,
+				 private);
 	      }
 
 	    oldval = mutex->__data.__lock;

nptl/pthread_mutex_timedlock.c

@@ -401,22 +401,10 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex,
 
 		    /* Delay the thread until the timeout is reached.
 		       Then return ETIMEDOUT.  */
-		    struct timespec reltime;
+		    do
-		    struct timespec now;
+		      e = lll_timedwait (&(int){0}, 0, clockid, abstime,
-
+					 private);
-		    INTERNAL_SYSCALL (clock_gettime, __err, 2, clockid,
+		    while (e != ETIMEDOUT);
-				      &now);
-		    reltime.tv_sec = abstime->tv_sec - now.tv_sec;
-		    reltime.tv_nsec = abstime->tv_nsec - now.tv_nsec;
-		    if (reltime.tv_nsec < 0)
-		      {
-			reltime.tv_nsec += 1000000000;
-			--reltime.tv_sec;
-		      }
-		    if (reltime.tv_sec >= 0)
-		      while (__nanosleep_nocancel (&reltime, &reltime) != 0)
-			continue;
-
 		    return ETIMEDOUT;
 		  }
 

sysdeps/nptl/lowlevellock.h

@@ -21,6 +21,7 @@
 
 #include <atomic.h>
 #include <lowlevellock-futex.h>
+#include <time.h>
 
 /* Low-level locks use a combination of atomic operations (to acquire and
    release lock ownership) and futex operations (to block until the state
@@ -121,10 +122,12 @@ extern void __lll_lock_wait (int *futex, int private) attribute_hidden;
 #define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private)
 
 
-extern int __lll_clocklock_wait (int *futex, clockid_t,
+extern int __lll_clocklock_wait (int *futex, int val, clockid_t,
 				 const struct timespec *,
 				 int private) attribute_hidden;
 
+#define lll_timedwait(futex, val, clockid, abstime, private)		\
+  __lll_clocklock_wait (futex, val, clockid, abstime, private)
 
 /* As __lll_lock, but with an absolute timeout measured against the clock
    specified in CLOCKID.  If the timeout occurs then return ETIMEDOUT. If
@@ -136,7 +139,15 @@ extern int __lll_clocklock_wait (int *futex, clockid_t,
                                                                 \
     if (__glibc_unlikely                                        \
         (atomic_compare_and_exchange_bool_acq (__futex, 1, 0))) \
-      __val = __lll_clocklock_wait (__futex, clockid, abstime, private); \
+      {								\
+	while (atomic_exchange_acq (futex, 2) != 0)		\
+	  {							\
+	    __val = __lll_clocklock_wait (__futex, 2, clockid, 	\
+					  abstime, private);	\
+	    if (__val == EINVAL || __val == ETIMEDOUT)		\
+	      break;						\
+	  }							\
+      }								\
     __val;                                                      \
   })
 #define lll_clocklock(futex, clockid, abstime, private)         \

sysdeps/sparc/sparc32/lll_timedlock_wait.c

@@ -1 +0,0 @@
-/* __lll_clocklock_wait is in lowlevellock.c.  */

sysdeps/sparc/sparc32/lowlevellock.c

@@ -50,46 +50,4 @@ __lll_lock_wait (int *futex, int private)
     }
   while (atomic_compare_and_exchange_val_24_acq (futex, 2, 0) != 0);
 }
-
-
-int
-__lll_clocklock_wait (int *futex, clockid_t clockid,
-                      const struct timespec *abstime, int private)
-{
-  /* Reject invalid timeouts.  */
-  if (! valid_nanoseconds (abstime->tv_nsec))
-    return EINVAL;
-
-  do
-    {
-      struct timespec ts;
-      struct timespec rt;
-
-      /* Get the current time. This can only fail if clockid is not
-         valid. */
-      if (__glibc_unlikely (__clock_gettime (clockid, &ts) != 0))
-        return EINVAL;
-
-      /* Compute relative timeout.  */
-      rt.tv_sec = abstime->tv_sec - ts.tv_sec;
-      rt.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
-      if (rt.tv_nsec < 0)
-	{
-	  rt.tv_nsec += 1000000000;
-	  --rt.tv_sec;
-	}
-
-      /* Already timed out?  */
-      if (rt.tv_sec < 0)
-	return ETIMEDOUT;
-
-      /* Wait.  */
-      int oldval = atomic_compare_and_exchange_val_24_acq (futex, 2, 1);
-      if (oldval != 0)
-	lll_futex_timed_wait (futex, 2, &rt, private);
-    }
-  while (atomic_compare_and_exchange_val_24_acq (futex, 2, 0) != 0);
-
-  return 0;
-}
 #endif

sysdeps/unix/sysv/linux/sparc/lowlevellock.h

@@ -24,6 +24,7 @@
 #include <bits/pthreadtypes.h>
 #include <atomic.h>
 #include <kernel-features.h>
+#include <errno.h>
 
 #include <lowlevellock-futex.h>
 
@@ -75,9 +76,13 @@ __lll_cond_lock (int *futex, int private)
 #define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private)
 
 
-extern int __lll_clocklock_wait (int *futex, clockid_t, const struct timespec *,
+extern int __lll_clocklock_wait (int *futex, clockid_t, int val,
+				 const struct timespec *,
 				 int private) attribute_hidden;
 
+#define lll_timedwait(futex, val, clockid, abstime, private)		\
+  __lll_clocklock_wait (futex, val, clockid, abstime, private)
+
 static inline int
 __attribute__ ((always_inline))
 __lll_clocklock (int *futex, clockid_t clockid,
@@ -87,7 +92,20 @@ __lll_clocklock (int *futex, clockid_t clockid,
   int result = 0;
 
   if (__glibc_unlikely (val != 0))
-    result = __lll_clocklock_wait (futex, clockid, abstime, private);
+    {
+      do
+	{
+	  int oldval = atomic_compare_and_exchange_val_24_acq (futex, val, 1);
+	  if (oldval != 0)
+	    {
+	      result = __lll_clocklock_wait (futex, 2, clockid, abstime,
+					     private);
+	      if (result == EINVAL || result == ETIMEDOUT)
+		break;
+	    }
+        }
+      while (atomic_compare_and_exchange_val_24_acq (futex, val, 0) != 0);
+    }
   return result;
 }
 #define lll_clocklock(futex, clockid, abstime, private)  \