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author | Rich Felker <dalias@aerifal.cx> | 2018-05-09 00:14:13 -0400 |
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committer | Rich Felker <dalias@aerifal.cx> | 2018-05-09 00:36:09 -0400 |
commit | b8742f32602add243ee2ce74d804015463726899 (patch) | |
tree | 5a511e7d917a38bab0c2bb3aaa7457e6dd85e797 | |
parent | 1db9a35569d51155eb7f2ccf26d420ae4e42e416 (diff) | |
download | musl-b8742f32602add243ee2ce74d804015463726899.tar.gz musl-b8742f32602add243ee2ce74d804015463726899.tar.bz2 musl-b8742f32602add243ee2ce74d804015463726899.tar.xz musl-b8742f32602add243ee2ce74d804015463726899.zip |
improve design of thread-start with explicit scheduling attributes
eliminate the awkward startlock mechanism and corresponding fields of
the pthread structure that were only used at startup.
instead of having pthread_create perform the scheduling operations and
having the new thread wait for them to be completed, start the new
thread with a wrapper start function that performs its own scheduling,
sending the result code back via a futex. this way the new thread can
use storage from the calling thread's stack rather than permanent
fields in the pthread structure.
-rw-r--r-- | src/internal/pthread_impl.h | 2 | ||||
-rw-r--r-- | src/thread/pthread_create.c | 60 |
2 files changed, 39 insertions, 23 deletions
diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h index fc2def63..69352ef2 100644 --- a/src/internal/pthread_impl.h +++ b/src/internal/pthread_impl.h @@ -47,8 +47,6 @@ struct pthread { volatile int timer_id; locale_t locale; volatile int killlock[1]; - volatile int startlock[1]; - unsigned long sigmask[_NSIG/8/sizeof(long)]; char *dlerror_buf; void *stdio_locks; diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c index e07d29e3..5f07ab49 100644 --- a/src/thread/pthread_create.c +++ b/src/thread/pthread_create.c @@ -132,22 +132,36 @@ void __do_cleanup_pop(struct __ptcb *cb) __pthread_self()->cancelbuf = cb->__next; } +struct start_sched_args { + void *start_arg; + void *(*start_fn)(void *); + sigset_t mask; + pthread_attr_t *attr; + volatile int futex; +}; + +static void *start_sched(void *p) +{ + struct start_sched_args *ssa = p; + void *start_arg = ssa->start_arg; + void *(*start_fn)(void *) = ssa->start_fn; + pthread_t self = __pthread_self(); + + int ret = -__syscall(SYS_sched_setscheduler, self->tid, + ssa->attr->_a_policy, &ssa->attr->_a_prio); + if (!ret) __restore_sigs(&ssa->mask); + a_store(&ssa->futex, ret); + __wake(&ssa->futex, 1, 1); + if (ret) { + self->detach_state = DT_DYNAMIC; + return 0; + } + return start_fn(start_arg); +} + static int start(void *p) { pthread_t self = p; - /* States for startlock: - * 0 = no need for start sync - * 1 = waiting for parent to do work - * 2 = failure in parent, child must abort - * 3 = success in parent, child must restore sigmask */ - if (self->startlock[0]) { - __wait(self->startlock, 0, 1, 1); - if (self->startlock[0] == 2) { - self->detach_state = DT_DYNAMIC; - pthread_exit(0); - } - __restore_sigs(self->sigmask); - } if (self->unblock_cancel) __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, SIGPT_SET, 0, _NSIG/8); @@ -198,6 +212,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED; int do_sched = 0; pthread_attr_t attr = { 0 }; + struct start_sched_args ssa; if (!libc.can_do_threads) return ENOSYS; self = __pthread_self(); @@ -282,8 +297,14 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att new->detach_state = DT_JOINABLE; } if (attr._a_sched) { - do_sched = new->startlock[0] = 1; - __block_app_sigs(new->sigmask); + do_sched = 1; + ssa.futex = -1; + ssa.start_fn = new->start; + ssa.start_arg = new->start_arg; + ssa.attr = &attr; + new->start = start_sched; + new->start_arg = &ssa; + __block_app_sigs(&ssa.mask); } new->robust_list.head = &new->robust_list.head; new->unblock_cancel = self->cancel; @@ -295,7 +316,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att __release_ptc(); if (do_sched) { - __restore_sigs(new->sigmask); + __restore_sigs(&ssa.mask); } if (ret < 0) { @@ -305,11 +326,8 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att } if (do_sched) { - ret = __syscall(SYS_sched_setscheduler, new->tid, - attr._a_policy, &attr._a_prio); - a_store(new->startlock, ret<0 ? 2 : 3); - __wake(new->startlock, 1, 1); - if (ret < 0) return -ret; + __futexwait(&ssa.futex, -1, 1); + if (ret) return ret; } *res = new; |