5008a9424b
Summary: CloudABI provides two different types of futex objects: read-write locks and condition variables. There is no need to provide separate support for once objects and thread joining, as these are efficiently simulated by blocking on a read-write lock. Mutexes simply use read-write locks. Condition variables always have a lock object associated to them. They always know to which lock a thread needs to be migrated if woken up. This allows us to implement requeueing. A broadcast on a condition variable will never cause multiple threads to be woken up at once. They will be woken up iteratively. This implementation still has lots of room for improvement. Locking is coarse and right now we use linked lists to store all of the locks and condition variables, instead of using a hash table. The primary goal of this implementation was to behave correctly. Performance will be improved as we go. Test Plan: This futex implementation has been in use for the last couple of months and seems to work pretty well. All of the cloudlibc and libc++ unit tests seem to pass. Reviewers: dchagin, kib, vangyzen Subscribers: imp Differential Revision: https://reviews.freebsd.org/D3148
134 lines
3.8 KiB
C
134 lines
3.8 KiB
C
/*-
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* Copyright (c) 2015 Nuxi, https://nuxi.nl/
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/proc.h>
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#include <sys/stdint.h>
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#include <sys/syscallsubr.h>
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#include <compat/cloudabi/cloudabi_proto.h>
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#include <compat/cloudabi/cloudabi_syscalldefs.h>
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#include <compat/cloudabi/cloudabi_util.h>
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/* Converts a CloudABI clock ID to a FreeBSD clock ID. */
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static int
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cloudabi_convert_clockid(cloudabi_clockid_t in, clockid_t *out)
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{
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switch (in) {
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case CLOUDABI_CLOCK_MONOTONIC:
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*out = CLOCK_MONOTONIC;
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return (0);
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case CLOUDABI_CLOCK_PROCESS_CPUTIME_ID:
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*out = CLOCK_PROCESS_CPUTIME_ID;
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return (0);
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case CLOUDABI_CLOCK_REALTIME:
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*out = CLOCK_REALTIME;
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return (0);
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case CLOUDABI_CLOCK_THREAD_CPUTIME_ID:
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*out = CLOCK_THREAD_CPUTIME_ID;
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return (0);
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default:
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return (EINVAL);
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}
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}
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/* Converts a struct timespec to a CloudABI timestamp. */
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int
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cloudabi_convert_timespec(const struct timespec *in, cloudabi_timestamp_t *out)
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{
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cloudabi_timestamp_t s, ns;
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if (in->tv_sec < 0) {
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/* Timestamps from before the Epoch cannot be expressed. */
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*out = 0;
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return (EOVERFLOW);
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}
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s = in->tv_sec;
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ns = in->tv_nsec;
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if (s > UINT64_MAX / 1000000000 ||
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(s == UINT64_MAX / 1000000000 && ns > UINT64_MAX % 1000000000)) {
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/* Addition of seconds and nanoseconds would overflow. */
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*out = UINT64_MAX;
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return (EOVERFLOW);
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}
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*out = s * 1000000000 + ns;
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return (0);
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}
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/* Fetches the time value of a clock. */
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int
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cloudabi_clock_time_get(struct thread *td, cloudabi_clockid_t clock_id,
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cloudabi_timestamp_t *ret)
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{
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struct timespec ts;
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int error;
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clockid_t clockid;
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error = cloudabi_convert_clockid(clock_id, &clockid);
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if (error != 0)
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return (error);
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error = kern_clock_gettime(td, clockid, &ts);
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if (error != 0)
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return (error);
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return (cloudabi_convert_timespec(&ts, ret));
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}
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int
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cloudabi_sys_clock_res_get(struct thread *td,
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struct cloudabi_sys_clock_res_get_args *uap)
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{
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struct timespec ts;
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cloudabi_timestamp_t cts;
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int error;
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clockid_t clockid;
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error = cloudabi_convert_clockid(uap->clock_id, &clockid);
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if (error != 0)
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return (error);
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error = kern_clock_getres(td, clockid, &ts);
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if (error != 0)
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return (error);
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error = cloudabi_convert_timespec(&ts, &cts);
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if (error != 0)
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return (error);
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td->td_retval[0] = cts;
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return (0);
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}
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int
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cloudabi_sys_clock_time_get(struct thread *td,
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struct cloudabi_sys_clock_time_get_args *uap)
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{
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cloudabi_timestamp_t ts;
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int error;
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error = cloudabi_clock_time_get(td, uap->clock_id, &ts);
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td->td_retval[0] = ts;
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return (error);
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}
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