From: Lennart Poettering Date: Thu, 26 Jul 2007 13:14:26 +0000 (+0000) Subject: add abstracted file descriptor based semaphore object that is lock-free in the best... X-Git-Tag: submit/2.0-panda/20130828.192557~2837^2~1^2~429 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6ad165c68615bacc10213e99a2dd485b5d1f8ed1;p=profile%2Fivi%2Fpulseaudio-panda.git add abstracted file descriptor based semaphore object that is lock-free in the best cases git-svn-id: file:///home/lennart/svn/public/pulseaudio/branches/lennart@1537 fefdeb5f-60dc-0310-8127-8f9354f1896f --- diff --git a/src/pulsecore/fdsem.c b/src/pulsecore/fdsem.c new file mode 100644 index 0000000..4de531a --- /dev/null +++ b/src/pulsecore/fdsem.c @@ -0,0 +1,189 @@ +/* $Id$ */ + +/*** + This file is part of PulseAudio. + + Copyright 2006 Lennart Poettering + + PulseAudio 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. + + PulseAudio 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 PulseAudio; if not, write to the Free Software + Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 + USA. +***/ + +#ifdef HAVE_CONFIG_H +#include +#endif + +#include +#include + +#include +#include +#include +#include +#include +#include + +#include "fdsem.h" + +struct pa_fdsem { + int fds[2]; + pa_atomic_t waiting; + pa_atomic_t signalled; + pa_atomic_t in_pipe; +}; + +pa_fdsem *pa_fdsem_new(void) { + pa_fdsem *f; + + f = pa_xnew(pa_fdsem, 1); + + if (pipe(f->fds) < 0) { + pa_xfree(f); + return NULL; + } + + pa_atomic_store(&f->waiting, 0); + pa_atomic_store(&f->signalled, 0); + pa_atomic_store(&f->in_pipe, 0); + + return f; +} + +void pa_fdsem_free(pa_fdsem *f) { + pa_assert(f); + + pa_assert(pa_atomic_load(&f->waiting) == 0); + + close(f->fds[0]); + close(f->fds[1]); + + pa_xfree(f); +} + +static void flush(pa_fdsem *f) { + ssize_t r; + pa_assert(f); + + if (pa_atomic_load(&f->in_pipe) <= 0) + return; + + do { + char x[10]; + + if ((r = read(f->fds[0], &x, sizeof(x))) <= 0) { + pa_assert(r < 0 && errno == EINTR); + continue; + } + + } while (pa_atomic_sub(&f->in_pipe, r) > r); +} + +void pa_fdsem_post(pa_fdsem *f) { + pa_assert(f); + + if (pa_atomic_cmpxchg(&f->signalled, 0, 1)) { + + if (pa_atomic_load(&f->waiting)) { + ssize_t r; + char x = 'x'; + + pa_atomic_inc(&f->in_pipe); + + for (;;) { + + if ((r = write(f->fds[1], &x, 1)) != 1) { + pa_assert(r < 0 && errno == EINTR); + continue; + } + + break; + } + } + } +} + +void pa_fdsem_wait(pa_fdsem *f) { + pa_assert(f); + + flush(f); + + if (pa_atomic_cmpxchg(&f->signalled, 1, 0)) + return; + + pa_atomic_inc(&f->waiting); + + while (!pa_atomic_cmpxchg(&f->signalled, 1, 0)) { + char x[10]; + ssize_t r; + + if ((r = read(f->fds[0], &x, sizeof(x))) <= 0) { + pa_assert(r < 0 && errno == EINTR); + continue; + } + + pa_atomic_sub(&f->in_pipe, r); + } + + pa_atomic_dec(&f->waiting); +} + +int pa_fdsem_try(pa_fdsem *f) { + pa_assert(f); + + flush(f); + + if (pa_atomic_cmpxchg(&f->signalled, 1, 0)) + return 1; + + return 0; +} + + +int pa_fdsem_get(pa_fdsem *f) { + pa_assert(f); + + return f->fds[0]; +} + +int pa_fdsem_before_poll(pa_fdsem *f) { + pa_assert(f); + + flush(f); + + if (pa_atomic_cmpxchg(&f->signalled, 1, 0)) + return -1; + + pa_atomic_inc(&f->waiting); + + if (pa_atomic_cmpxchg(&f->signalled, 1, 0)) { + pa_atomic_dec(&f->waiting); + return -1; + } + + return 0; +} + +int pa_fdsem_after_poll(pa_fdsem *f) { + pa_assert(f); + + pa_atomic_dec(&f->waiting); + + flush(f); + + if (pa_atomic_cmpxchg(&f->signalled, 1, 0)) + return 1; + + return 0; +} diff --git a/src/pulsecore/fdsem.h b/src/pulsecore/fdsem.h new file mode 100644 index 0000000..f38ef20 --- /dev/null +++ b/src/pulsecore/fdsem.h @@ -0,0 +1,49 @@ +#ifndef foopulsefdsemhfoo +#define foopulsefdsemhfoo + +/* $Id$ */ + +/*** + This file is part of PulseAudio. + + Copyright 2004-2006 Lennart Poettering + + PulseAudio 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. + + PulseAudio 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 PulseAudio; if not, write to the Free Software + Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 + USA. +***/ + +#include +#include + +/* A simple, asynchronous semaphore which uses fds for sleeping. In + * the best case all functions are lock-free unless sleeping is + * required. */ + +typedef struct pa_fdsem pa_fdsem; + +pa_fdsem *pa_fdsem_new(void); +void pa_fdsem_free(pa_fdsem *f); + +void pa_fdsem_post(pa_fdsem *f); +void pa_fdsem_wait(pa_fdsem *f); +int pa_fdsem_try(pa_fdsem *f); + +int pa_fdsem_get(pa_fdsem *f); + +int pa_fdsem_before_poll(pa_fdsem *f); +int pa_fdsem_after_poll(pa_fdsem *f); + + +#endif