From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: [PATCH RFC alsa-lib 5/5] pcm: Remove home brew atomic operations Date: Tue, 5 Jul 2016 17:20:24 +0200 Message-ID: <20160705152024.20152-6-tiwai@suse.de> References: <20160705152024.20152-1-tiwai@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by alsa0.perex.cz (Postfix) with ESMTP id 5E8ED2663DF for ; Tue, 5 Jul 2016 17:20:28 +0200 (CEST) Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 97213AD44 for ; Tue, 5 Jul 2016 15:20:27 +0000 (UTC) In-Reply-To: <20160705152024.20152-1-tiwai@suse.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org We've had a few home brew atomic operations in a couple of places in the PCM code. This was for supporting the concurrent accesses, but in practice, it couldn't cover the race properly by itself alone. Since we have a wider concurrency protection via mutex now, we can get rid of these atomic codes, which worsens the portability significantly. Signed-off-by: Takashi Iwai --- include/Makefile.am | 2 +- include/iatomic.h | 170 --------------------------------------------------- src/pcm/Makefile.am | 2 +- src/pcm/atomic.c | 43 ------------- src/pcm/pcm_plugin.c | 72 +++++----------------- src/pcm/pcm_plugin.h | 2 - src/pcm/pcm_rate.c | 34 ++--------- 7 files changed, 20 insertions(+), 305 deletions(-) delete mode 100644 include/iatomic.h delete mode 100644 src/pcm/atomic.c diff --git a/include/Makefile.am b/include/Makefile.am index 31a3f748dc46..67f32e36c911 100644 --- a/include/Makefile.am +++ b/include/Makefile.am @@ -5,7 +5,7 @@ alsaincludedir = ${includedir}/alsa alsainclude_HEADERS = asoundlib.h asoundef.h \ version.h global.h input.h output.h error.h \ - conf.h control.h iatomic.h + conf.h control.h if BUILD_CTL_PLUGIN_EXT alsainclude_HEADERS += control_external.h diff --git a/include/iatomic.h b/include/iatomic.h deleted file mode 100644 index acdd3e29c13a..000000000000 --- a/include/iatomic.h +++ /dev/null @@ -1,170 +0,0 @@ -#ifndef __ALSA_IATOMIC_H -#define __ALSA_IATOMIC_H - -#ifdef __i386__ -#define mb() __asm__ __volatile__ ("lock; addl $0,0(%%esp)": : :"memory") -#define rmb() mb() -#define wmb() __asm__ __volatile__ ("": : :"memory") -#define IATOMIC_DEFINED 1 -#endif - -#ifdef __x86_64__ -#define mb() asm volatile("mfence":::"memory") -#define rmb() asm volatile("lfence":::"memory") -#define wmb() asm volatile("sfence":::"memory") -#define IATOMIC_DEFINED 1 -#endif - -#ifdef __ia64__ -/* - * Macros to force memory ordering. In these descriptions, "previous" - * and "subsequent" refer to program order; "visible" means that all - * architecturally visible effects of a memory access have occurred - * (at a minimum, this means the memory has been read or written). - * - * wmb(): Guarantees that all preceding stores to memory- - * like regions are visible before any subsequent - * stores and that all following stores will be - * visible only after all previous stores. - * rmb(): Like wmb(), but for reads. - * mb(): wmb()/rmb() combo, i.e., all previous memory - * accesses are visible before all subsequent - * accesses and vice versa. This is also known as - * a "fence." - * - * Note: "mb()" and its variants cannot be used as a fence to order - * accesses to memory mapped I/O registers. For that, mf.a needs to - * be used. However, we don't want to always use mf.a because (a) - * it's (presumably) much slower than mf and (b) mf.a is supported for - * sequential memory pages only. - */ -#define mb() __asm__ __volatile__ ("mf" ::: "memory") -#define rmb() mb() -#define wmb() mb() - -#define IATOMIC_DEFINED 1 - -#endif /* __ia64__ */ - -#ifdef __alpha__ - -#define mb() \ -__asm__ __volatile__("mb": : :"memory") - -#define rmb() \ -__asm__ __volatile__("mb": : :"memory") - -#define wmb() \ -__asm__ __volatile__("wmb": : :"memory") - -#define IATOMIC_DEFINED 1 - -#endif /* __alpha__ */ - -#ifdef __powerpc__ - -/* - * Memory barrier. - * The sync instruction guarantees that all memory accesses initiated - * by this processor have been performed (with respect to all other - * mechanisms that access memory). The eieio instruction is a barrier - * providing an ordering (separately) for (a) cacheable stores and (b) - * loads and stores to non-cacheable memory (e.g. I/O devices). - * - * mb() prevents loads and stores being reordered across this point. - * rmb() prevents loads being reordered across this point. - * wmb() prevents stores being reordered across this point. - * - * We can use the eieio instruction for wmb, but since it doesn't - * give any ordering guarantees about loads, we have to use the - * stronger but slower sync instruction for mb and rmb. - */ -#define mb() __asm__ __volatile__ ("sync" : : : "memory") -#define rmb() __asm__ __volatile__ ("sync" : : : "memory") -#define wmb() __asm__ __volatile__ ("eieio" : : : "memory") - -#define IATOMIC_DEFINED 1 - -#endif /* __powerpc__ */ - -#ifndef IATOMIC_DEFINED - -/* Generic __sync_synchronize is available from gcc 4.1 */ - -#define mb() __sync_synchronize() -#define rmb() mb() -#define wmb() mb() - -#define IATOMIC_DEFINED 1 - -#endif /* IATOMIC_DEFINED */ - -/* - * Atomic read/write - * Copyright (c) 2001 by Abramo Bagnara - */ - -/* Max number of times we must spin on a spin-lock calling sched_yield(). - After MAX_SPIN_COUNT iterations, we put the calling thread to sleep. */ - -#ifndef MAX_SPIN_COUNT -#define MAX_SPIN_COUNT 50 -#endif - -/* Duration of sleep (in nanoseconds) when we can't acquire a spin-lock - after MAX_SPIN_COUNT iterations of sched_yield(). - This MUST BE > 2ms. - (Otherwise the kernel does busy-waiting for real-time threads, - giving other threads no chance to run.) */ - -#ifndef SPIN_SLEEP_DURATION -#define SPIN_SLEEP_DURATION 2000001 -#endif - -typedef struct { - unsigned int begin, end; -} snd_atomic_write_t; - -typedef struct { - volatile const snd_atomic_write_t *write; - unsigned int end; -} snd_atomic_read_t; - -void snd_atomic_read_wait(snd_atomic_read_t *t); - -static __inline__ void snd_atomic_write_init(snd_atomic_write_t *w) -{ - w->begin = 0; - w->end = 0; -} - -static __inline__ void snd_atomic_write_begin(snd_atomic_write_t *w) -{ - w->begin++; - wmb(); -} - -static __inline__ void snd_atomic_write_end(snd_atomic_write_t *w) -{ - wmb(); - w->end++; -} - -static __inline__ void snd_atomic_read_init(snd_atomic_read_t *r, snd_atomic_write_t *w) -{ - r->write = w; -} - -static __inline__ void snd_atomic_read_begin(snd_atomic_read_t *r) -{ - r->end = r->write->end; - rmb(); -} - -static __inline__ int snd_atomic_read_ok(snd_atomic_read_t *r) -{ - rmb(); - return r->end == r->write->begin; -} - -#endif /* __ALSA_IATOMIC_H */ diff --git a/src/pcm/Makefile.am b/src/pcm/Makefile.am index 81598f634bc3..8edbd0b5c719 100644 --- a/src/pcm/Makefile.am +++ b/src/pcm/Makefile.am @@ -3,7 +3,7 @@ DIST_SUBDIRS = scopes EXTRA_LTLIBRARIES = libpcm.la -libpcm_la_SOURCES = atomic.c mask.c interval.c \ +libpcm_la_SOURCES = mask.c interval.c \ pcm.c pcm_params.c pcm_simple.c \ pcm_hw.c pcm_misc.c pcm_mmap.c pcm_symbols.c diff --git a/src/pcm/atomic.c b/src/pcm/atomic.c deleted file mode 100644 index 75659457af76..000000000000 --- a/src/pcm/atomic.c +++ /dev/null @@ -1,43 +0,0 @@ -/* - * Atomic read/write - * Copyright (c) 2001 by Abramo Bagnara - * - * This 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. - * - * This program 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 this library; if not, write to the Free Software - * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA - * - */ - -#include -#include -#include -#include "iatomic.h" - -void snd_atomic_read_wait(snd_atomic_read_t *t) -{ - volatile const snd_atomic_write_t *w = t->write; - unsigned int loops = 0; - struct timespec ts; - while (w->begin != w->end) { - if (loops < MAX_SPIN_COUNT) { - sched_yield(); - loops++; - continue; - } - loops = 0; - ts.tv_sec = 0; - ts.tv_nsec = SPIN_SLEEP_DURATION; - nanosleep(&ts, NULL); - } -} - diff --git a/src/pcm/pcm_plugin.c b/src/pcm/pcm_plugin.c index 8527783c3569..e53c5bb5568e 100644 --- a/src/pcm/pcm_plugin.c +++ b/src/pcm/pcm_plugin.c @@ -133,7 +133,6 @@ void snd_pcm_plugin_init(snd_pcm_plugin_t *plugin) memset(plugin, 0, sizeof(snd_pcm_plugin_t)); plugin->undo_read = snd_pcm_plugin_undo_read; plugin->undo_write = snd_pcm_plugin_undo_write; - snd_atomic_write_init(&plugin->watom); } static int snd_pcm_plugin_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delayp) @@ -157,15 +156,11 @@ static int snd_pcm_plugin_prepare(snd_pcm_t *pcm) { snd_pcm_plugin_t *plugin = pcm->private_data; int err; - snd_atomic_write_begin(&plugin->watom); err = snd_pcm_prepare(plugin->gen.slave); - if (err < 0) { - snd_atomic_write_end(&plugin->watom); + if (err < 0) return err; - } *pcm->hw.ptr = 0; *pcm->appl.ptr = 0; - snd_atomic_write_end(&plugin->watom); if (plugin->init) { err = plugin->init(pcm); if (err < 0) @@ -178,15 +173,11 @@ static int snd_pcm_plugin_reset(snd_pcm_t *pcm) { snd_pcm_plugin_t *plugin = pcm->private_data; int err; - snd_atomic_write_begin(&plugin->watom); err = snd_pcm_reset(plugin->gen.slave); - if (err < 0) { - snd_atomic_write_end(&plugin->watom); + if (err < 0) return err; - } *pcm->hw.ptr = 0; *pcm->appl.ptr = 0; - snd_atomic_write_end(&plugin->watom); if (plugin->init) { err = plugin->init(pcm); if (err < 0) @@ -212,14 +203,10 @@ snd_pcm_sframes_t snd_pcm_plugin_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t frames return 0; sframes = frames; - snd_atomic_write_begin(&plugin->watom); sframes = snd_pcm_rewind(plugin->gen.slave, sframes); - if (sframes < 0) { - snd_atomic_write_end(&plugin->watom); + if (sframes < 0) return sframes; - } snd_pcm_mmap_appl_backward(pcm, (snd_pcm_uframes_t) sframes); - snd_atomic_write_end(&plugin->watom); return (snd_pcm_sframes_t) sframes; } @@ -240,14 +227,10 @@ snd_pcm_sframes_t snd_pcm_plugin_forward(snd_pcm_t *pcm, snd_pcm_uframes_t frame return 0; sframes = frames; - snd_atomic_write_begin(&plugin->watom); sframes = INTERNAL(snd_pcm_forward)(plugin->gen.slave, sframes); - if (sframes < 0) { - snd_atomic_write_end(&plugin->watom); + if (sframes < 0) return sframes; - } snd_pcm_mmap_appl_forward(pcm, (snd_pcm_uframes_t) frames); - snd_atomic_write_end(&plugin->watom); return (snd_pcm_sframes_t) frames; } @@ -279,31 +262,27 @@ static snd_pcm_sframes_t snd_pcm_plugin_write_areas(snd_pcm_t *pcm, err = -EPIPE; goto error; } - snd_atomic_write_begin(&plugin->watom); result = snd_pcm_mmap_commit(slave, slave_offset, slave_frames); if (result > 0 && (snd_pcm_uframes_t)result != slave_frames) { snd_pcm_sframes_t res; res = plugin->undo_write(pcm, slave_areas, slave_offset + result, slave_frames, slave_frames - result); if (res < 0) { err = res; - goto error_atomic; + goto error; } frames -= res; } if (result <= 0) { err = result; - goto error_atomic; + goto error; } snd_pcm_mmap_appl_forward(pcm, frames); - snd_atomic_write_end(&plugin->watom); offset += frames; xfer += frames; size -= frames; } return (snd_pcm_sframes_t)xfer; - error_atomic: - snd_atomic_write_end(&plugin->watom); error: return xfer > 0 ? (snd_pcm_sframes_t)xfer : err; } @@ -336,7 +315,6 @@ static snd_pcm_sframes_t snd_pcm_plugin_read_areas(snd_pcm_t *pcm, err = -EPIPE; goto error; } - snd_atomic_write_begin(&plugin->watom); result = snd_pcm_mmap_commit(slave, slave_offset, slave_frames); if (result > 0 && (snd_pcm_uframes_t)result != slave_frames) { snd_pcm_sframes_t res; @@ -344,24 +322,21 @@ static snd_pcm_sframes_t snd_pcm_plugin_read_areas(snd_pcm_t *pcm, res = plugin->undo_read(slave, areas, offset, frames, slave_frames - result); if (res < 0) { err = res; - goto error_atomic; + goto error; } frames -= res; } if (result <= 0) { err = result; - goto error_atomic; + goto error; } snd_pcm_mmap_appl_forward(pcm, frames); - snd_atomic_write_end(&plugin->watom); offset += frames; xfer += frames; size -= frames; } return (snd_pcm_sframes_t)xfer; - error_atomic: - snd_atomic_write_end(&plugin->watom); error: return xfer > 0 ? (snd_pcm_sframes_t)xfer : err; } @@ -417,9 +392,7 @@ snd_pcm_plugin_mmap_commit(snd_pcm_t *pcm, int err; if (pcm->stream == SND_PCM_STREAM_CAPTURE) { - snd_atomic_write_begin(&plugin->watom); snd_pcm_mmap_appl_forward(pcm, size); - snd_atomic_write_end(&plugin->watom); return size; } slave_size = snd_pcm_avail_update(slave); @@ -443,7 +416,6 @@ snd_pcm_plugin_mmap_commit(snd_pcm_t *pcm, frames = cont; frames = plugin->write(pcm, areas, appl_offset, frames, slave_areas, slave_offset, &slave_frames); - snd_atomic_write_begin(&plugin->watom); result = snd_pcm_mmap_commit(slave, slave_offset, slave_frames); if (result > 0 && (snd_pcm_uframes_t)result != slave_frames) { snd_pcm_sframes_t res; @@ -451,16 +423,15 @@ snd_pcm_plugin_mmap_commit(snd_pcm_t *pcm, res = plugin->undo_write(pcm, slave_areas, slave_offset + result, slave_frames, slave_frames - result); if (res < 0) { err = res; - goto error_atomic; + goto error; } frames -= res; } if (result <= 0) { err = result; - goto error_atomic; + goto error; } snd_pcm_mmap_appl_forward(pcm, frames); - snd_atomic_write_end(&plugin->watom); if (frames == cont) appl_offset = 0; else @@ -475,8 +446,6 @@ snd_pcm_plugin_mmap_commit(snd_pcm_t *pcm, } return xfer; - error_atomic: - snd_atomic_write_end(&plugin->watom); error: return xfer > 0 ? xfer : err; } @@ -519,7 +488,6 @@ static snd_pcm_sframes_t snd_pcm_plugin_avail_update(snd_pcm_t *pcm) frames = cont; frames = (plugin->read)(pcm, areas, hw_offset, frames, slave_areas, slave_offset, &slave_frames); - snd_atomic_write_begin(&plugin->watom); result = snd_pcm_mmap_commit(slave, slave_offset, slave_frames); if (result > 0 && (snd_pcm_uframes_t)result != slave_frames) { snd_pcm_sframes_t res; @@ -527,16 +495,15 @@ static snd_pcm_sframes_t snd_pcm_plugin_avail_update(snd_pcm_t *pcm) res = plugin->undo_read(slave, areas, hw_offset, frames, slave_frames - result); if (res < 0) { err = res; - goto error_atomic; + goto error; } frames -= res; } if (result <= 0) { err = result; - goto error_atomic; + goto error; } snd_pcm_mmap_hw_forward(pcm, frames); - snd_atomic_write_end(&plugin->watom); if (frames == cont) hw_offset = 0; else @@ -547,8 +514,6 @@ static snd_pcm_sframes_t snd_pcm_plugin_avail_update(snd_pcm_t *pcm) } return (snd_pcm_sframes_t)xfer; - error_atomic: - snd_atomic_write_end(&plugin->watom); error: return xfer > 0 ? (snd_pcm_sframes_t)xfer : err; } @@ -558,24 +523,15 @@ static int snd_pcm_plugin_status(snd_pcm_t *pcm, snd_pcm_status_t * status) { snd_pcm_plugin_t *plugin = pcm->private_data; snd_pcm_sframes_t err; - snd_atomic_read_t ratom; - snd_atomic_read_init(&ratom, &plugin->watom); - _again: - snd_atomic_read_begin(&ratom); + /* sync with the latest hw and appl ptrs */ snd_pcm_plugin_avail_update(pcm); err = snd_pcm_status(plugin->gen.slave, status); - if (err < 0) { - snd_atomic_read_ok(&ratom); + if (err < 0) return err; - } status->appl_ptr = *pcm->appl.ptr; status->hw_ptr = *pcm->hw.ptr; - if (!snd_atomic_read_ok(&ratom)) { - snd_atomic_read_wait(&ratom); - goto _again; - } return 0; } diff --git a/src/pcm/pcm_plugin.h b/src/pcm/pcm_plugin.h index b0a3e1869ea1..217f0757ea59 100644 --- a/src/pcm/pcm_plugin.h +++ b/src/pcm/pcm_plugin.h @@ -19,7 +19,6 @@ * */ -#include "iatomic.h" #include "pcm_generic.h" typedef snd_pcm_uframes_t (*snd_pcm_slave_xfer_areas_func_t) @@ -46,7 +45,6 @@ typedef struct { snd_pcm_slave_xfer_areas_undo_func_t undo_write; int (*init)(snd_pcm_t *pcm); snd_pcm_uframes_t appl_ptr, hw_ptr; - snd_atomic_write_t watom; } snd_pcm_plugin_t; /* make local functions really local */ diff --git a/src/pcm/pcm_rate.c b/src/pcm/pcm_rate.c index 0fe466647a55..e44bd21be8c9 100644 --- a/src/pcm/pcm_rate.c +++ b/src/pcm/pcm_rate.c @@ -32,7 +32,6 @@ #include "pcm_local.h" #include "pcm_plugin.h" #include "pcm_rate.h" -#include "iatomic.h" #include "plugin_ops.h" @@ -51,7 +50,6 @@ typedef struct _snd_pcm_rate snd_pcm_rate_t; struct _snd_pcm_rate { snd_pcm_generic_t gen; - snd_atomic_write_t watom; snd_pcm_uframes_t appl_ptr, hw_ptr; snd_pcm_uframes_t last_commit_ptr; snd_pcm_uframes_t orig_avail_min; @@ -584,9 +582,7 @@ static int snd_pcm_rate_hwsync(snd_pcm_t *pcm) int err = snd_pcm_hwsync(rate->gen.slave); if (err < 0) return err; - snd_atomic_write_begin(&rate->watom); snd_pcm_rate_sync_hwptr(pcm); - snd_atomic_write_end(&rate->watom); return 0; } @@ -602,15 +598,11 @@ static int snd_pcm_rate_prepare(snd_pcm_t *pcm) snd_pcm_rate_t *rate = pcm->private_data; int err; - snd_atomic_write_begin(&rate->watom); err = snd_pcm_prepare(rate->gen.slave); - if (err < 0) { - snd_atomic_write_end(&rate->watom); + if (err < 0) return err; - } *pcm->hw.ptr = 0; *pcm->appl.ptr = 0; - snd_atomic_write_end(&rate->watom); err = snd_pcm_rate_init(pcm); if (err < 0) return err; @@ -621,15 +613,11 @@ static int snd_pcm_rate_reset(snd_pcm_t *pcm) { snd_pcm_rate_t *rate = pcm->private_data; int err; - snd_atomic_write_begin(&rate->watom); err = snd_pcm_reset(rate->gen.slave); - if (err < 0) { - snd_atomic_write_end(&rate->watom); + if (err < 0) return err; - } *pcm->hw.ptr = 0; *pcm->appl.ptr = 0; - snd_atomic_write_end(&rate->watom); err = snd_pcm_rate_init(pcm); if (err < 0) return err; @@ -923,9 +911,7 @@ static snd_pcm_sframes_t snd_pcm_rate_mmap_commit(snd_pcm_t *pcm, if (err < 0) return err; } - snd_atomic_write_begin(&rate->watom); snd_pcm_mmap_appl_forward(pcm, size); - snd_atomic_write_end(&rate->watom); return size; } @@ -938,9 +924,7 @@ static snd_pcm_sframes_t snd_pcm_rate_avail_update(snd_pcm_t *pcm) slave_size = snd_pcm_avail_update(slave); if (pcm->stream == SND_PCM_STREAM_CAPTURE) goto _capture; - snd_atomic_write_begin(&rate->watom); snd_pcm_rate_sync_hwptr(pcm); - snd_atomic_write_end(&rate->watom); snd_pcm_rate_sync_playback_area(pcm, rate->appl_ptr); return snd_pcm_mmap_avail(pcm); _capture: { @@ -1090,15 +1074,10 @@ static int snd_pcm_rate_status(snd_pcm_t *pcm, snd_pcm_status_t * status) { snd_pcm_rate_t *rate = pcm->private_data; snd_pcm_sframes_t err; - snd_atomic_read_t ratom; - snd_atomic_read_init(&ratom, &rate->watom); - _again: - snd_atomic_read_begin(&ratom); + err = snd_pcm_status(rate->gen.slave, status); - if (err < 0) { - snd_atomic_read_ok(&ratom); + if (err < 0) return err; - } if (pcm->stream == SND_PCM_STREAM_PLAYBACK) { if (rate->start_pending) status->state = SND_PCM_STATE_RUNNING; @@ -1116,10 +1095,6 @@ static int snd_pcm_rate_status(snd_pcm_t *pcm, snd_pcm_status_t * status) status->avail = snd_pcm_mmap_capture_avail(pcm); status->avail_max = rate->ops.output_frames(rate->obj, status->avail_max); } - if (!snd_atomic_read_ok(&ratom)) { - snd_atomic_read_wait(&ratom); - goto _again; - } return 0; } @@ -1309,7 +1284,6 @@ int snd_pcm_rate_open(snd_pcm_t **pcmp, const char *name, rate->gen.close_slave = close_slave; rate->srate = srate; rate->sformat = sformat; - snd_atomic_write_init(&rate->watom); err = snd_pcm_new(&pcm, SND_PCM_TYPE_RATE, name, slave->stream, slave->mode); if (err < 0) { -- 2.9.0