summaryrefslogtreecommitdiff
path: root/hurd/hurdlock.c
diff options
context:
space:
mode:
Diffstat (limited to 'hurd/hurdlock.c')
-rw-r--r--hurd/hurdlock.c220
1 files changed, 220 insertions, 0 deletions
diff --git a/hurd/hurdlock.c b/hurd/hurdlock.c
new file mode 100644
index 0000000000..382e9f2aa9
--- /dev/null
+++ b/hurd/hurdlock.c
@@ -0,0 +1,220 @@
+/* Hurd helpers for lowlevellocks.
+ Copyright (C) 1999-2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include "hurdlock.h"
+#include <hurd.h>
+#include <hurd/hurd.h>
+#include <time.h>
+#include <errno.h>
+#include <unistd.h>
+
+/* Convert an absolute timeout in nanoseconds to a relative
+ timeout in milliseconds. */
+static inline int __attribute__ ((gnu_inline))
+compute_reltime (const struct timespec *abstime, clockid_t clk)
+{
+ struct timespec ts;
+ __clock_gettime (clk, &ts);
+
+ ts.tv_sec = abstime->tv_sec - ts.tv_sec;
+ ts.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
+
+ if (ts.tv_nsec < 0)
+ {
+ --ts.tv_sec;
+ ts.tv_nsec += 1000000000;
+ }
+
+ return ts.tv_sec < 0 ? -1 : (int)(ts.tv_sec * 1000 + ts.tv_nsec / 1000000);
+}
+
+int
+__lll_abstimed_wait (void *ptr, int val,
+ const struct timespec *tsp, int flags, int clk)
+{
+ int mlsec = compute_reltime (tsp, clk);
+ return mlsec < 0 ? KERN_TIMEDOUT : lll_timed_wait (ptr, val, mlsec, flags);
+}
+
+int
+__lll_abstimed_xwait (void *ptr, int lo, int hi,
+ const struct timespec *tsp, int flags, int clk)
+{
+ int mlsec = compute_reltime (tsp, clk);
+ return mlsec < 0 ? KERN_TIMEDOUT : lll_timed_xwait (ptr, lo, hi, mlsec,
+ flags);
+}
+
+int
+__lll_abstimed_lock (void *ptr,
+ const struct timespec *tsp, int flags, int clk)
+{
+ if (lll_trylock (ptr) == 0)
+ return 0;
+
+ while (1)
+ {
+ if (atomic_exchange_acq ((int *)ptr, 2) == 0)
+ return 0;
+ else if (tsp->tv_nsec < 0 || tsp->tv_nsec >= 1000000000)
+ return EINVAL;
+
+ int mlsec = compute_reltime (tsp, clk);
+ if (mlsec < 0 || lll_timed_wait (ptr, 2, mlsec, flags) == KERN_TIMEDOUT)
+ return ETIMEDOUT;
+ }
+}
+
+/* Robust locks. */
+
+/* Test if a given process id is still valid. */
+static inline int
+valid_pid (int pid)
+{
+ task_t task = __pid2task (pid);
+ if (task == MACH_PORT_NULL)
+ return 0;
+
+ __mach_port_deallocate (__mach_task_self (), task);
+ return 1;
+}
+
+/* Robust locks have currently no support from the kernel; they
+ are simply implemented with periodic polling. When sleeping, the
+ maximum blocking time is determined by this constant. */
+#define MAX_WAIT_TIME 1500
+
+int
+__lll_robust_lock (void *ptr, int flags)
+{
+ int *iptr = (int *)ptr;
+ int id = __getpid ();
+ int wait_time = 25;
+ unsigned int val;
+
+ /* Try to set the lock word to our PID if it's clear. Otherwise,
+ mark it as having waiters. */
+ while (1)
+ {
+ val = *iptr;
+ if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
+ return 0;
+ else if (atomic_compare_and_exchange_bool_acq (iptr,
+ val | LLL_WAITERS, val) == 0)
+ break;
+ }
+
+ for (id |= LLL_WAITERS ; ; )
+ {
+ val = *iptr;
+ if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
+ return 0;
+ else if (val && !valid_pid (val & LLL_OWNER_MASK))
+ {
+ if (atomic_compare_and_exchange_bool_acq (iptr, id, val) == 0)
+ return EOWNERDEAD;
+ }
+ else
+ {
+ lll_timed_wait (iptr, val, wait_time, flags);
+ if (wait_time < MAX_WAIT_TIME)
+ wait_time <<= 1;
+ }
+ }
+}
+
+int
+__lll_robust_abstimed_lock (void *ptr,
+ const struct timespec *tsp, int flags, int clk)
+{
+ int *iptr = (int *)ptr;
+ int id = __getpid ();
+ int wait_time = 25;
+ unsigned int val;
+
+ while (1)
+ {
+ val = *iptr;
+ if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
+ return 0;
+ else if (atomic_compare_and_exchange_bool_acq (iptr,
+ val | LLL_WAITERS, val) == 0)
+ break;
+ }
+
+ for (id |= LLL_WAITERS ; ; )
+ {
+ val = *iptr;
+ if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
+ return 0;
+ else if (val && !valid_pid (val & LLL_OWNER_MASK))
+ {
+ if (atomic_compare_and_exchange_bool_acq (iptr, id, val) == 0)
+ return EOWNERDEAD;
+ }
+ else
+ {
+ int mlsec = compute_reltime (tsp, clk);
+ if (mlsec < 0)
+ return ETIMEDOUT;
+ else if (mlsec > wait_time)
+ mlsec = wait_time;
+
+ int res = lll_timed_wait (iptr, val, mlsec, flags);
+ if (res == KERN_TIMEDOUT)
+ return ETIMEDOUT;
+ else if (wait_time < MAX_WAIT_TIME)
+ wait_time <<= 1;
+ }
+ }
+}
+
+int
+__lll_robust_trylock (void *ptr)
+{
+ int *iptr = (int *)ptr;
+ int id = __getpid ();
+ unsigned int val = *iptr;
+
+ if (!val)
+ {
+ if (atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
+ return 0;
+ }
+ else if (!valid_pid (val & LLL_OWNER_MASK)
+ && atomic_compare_and_exchange_bool_acq (iptr, id, val) == 0)
+ return EOWNERDEAD;
+
+ return EBUSY;
+}
+
+void
+__lll_robust_unlock (void *ptr, int flags)
+{
+ unsigned int val = atomic_load_relaxed ((unsigned int *)ptr);
+ while (1)
+ {
+ if (val & LLL_WAITERS)
+ {
+ lll_set_wake (ptr, 0, flags);
+ break;
+ }
+ else if (atomic_compare_exchange_weak_release ((unsigned int *)ptr, &val, 0))
+ break;
+ }
+}