diff options
| author | riastradh <riastradh@NetBSD.org> | 2022-03-14 11:47:33 +0000 |
|---|---|---|
| committer | riastradh <riastradh@NetBSD.org> | 2022-03-14 11:47:33 +0000 |
| commit | 437cbf7c7c4277b018ff6dc1400733c67bc3ff71 (patch) | |
| tree | 74c3e73d238ee07db2ebd6b0be697e0eb95bcd48 /sys/dev/audio | |
| parent | a50614e285949fde660d815eebea253409eb95b7 (diff) | |
audio(4): Membar audit.
Won't affect anything on x86 because atomic r/m/w operations are
always full sequential consistency barriers, but might potentially
fix problems on, e.g., arm.
Note 1: I'm not clear on why the track lock is a bespoke mutex made
out of an atomic -- why not just mutex(9)?
Note 2: I'm not convinced the audio_mlog_flush synchronization is
correct; what happens if the softint runs on two CPUs at the same
time and swaps mlog_wpage simultaneously?
Note 3: Should maybe use atomic_load/store_relaxed for mlog_full and
mlog_drop, and atomic_inc/dec for mlog_refs.
Diffstat (limited to 'sys/dev/audio')
| -rw-r--r-- | sys/dev/audio/audio.c | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/sys/dev/audio/audio.c b/sys/dev/audio/audio.c index d22ea989a18..321eee1a829 100644 --- a/sys/dev/audio/audio.c +++ b/sys/dev/audio/audio.c @@ -1,4 +1,4 @@ -/* $NetBSD: audio.c,v 1.113 2021/12/12 13:05:13 andvar Exp $ */ +/* $NetBSD: audio.c,v 1.114 2022/03/14 11:47:33 riastradh Exp $ */ /*- * Copyright (c) 2008 The NetBSD Foundation, Inc. @@ -138,7 +138,7 @@ */ #include <sys/cdefs.h> -__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.113 2021/12/12 13:05:13 andvar Exp $"); +__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.114 2022/03/14 11:47:33 riastradh Exp $"); #ifdef _KERNEL_OPT #include "audio.h" @@ -162,6 +162,7 @@ __KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.113 2021/12/12 13:05:13 andvar Exp $"); #include <sys/kauth.h> #include <sys/kernel.h> #include <sys/kmem.h> +#include <sys/lock.h> #include <sys/malloc.h> #include <sys/mman.h> #include <sys/module.h> @@ -272,13 +273,14 @@ audio_mlog_flush(void) /* Nothing to do if already in use ? */ if (atomic_swap_32(&mlog_inuse, 1) == 1) return; + membar_enter(); int rpage = mlog_wpage; mlog_wpage ^= 1; mlog_buf[mlog_wpage][0] = '\0'; mlog_used = 0; - atomic_swap_32(&mlog_inuse, 0); + atomic_store_reease(&mlog_inuse, 0); if (mlog_buf[rpage][0] != '\0') { printf("%s", mlog_buf[rpage]); @@ -308,6 +310,7 @@ audio_mlog_printf(const char *fmt, ...) mlog_drop++; return; } + membar_enter(); va_start(ap, fmt); len = vsnprintf( @@ -321,7 +324,7 @@ audio_mlog_printf(const char *fmt, ...) mlog_full++; } - atomic_swap_32(&mlog_inuse, 0); + atomic_store_release(&mlog_inuse, 0); if (mlog_sih) softint_schedule(mlog_sih); @@ -1652,7 +1655,11 @@ audio_track_waitio(struct audio_softc *sc, audio_track_t *track) static __inline bool audio_track_lock_tryenter(audio_track_t *track) { - return (atomic_cas_uint(&track->lock, 0, 1) == 0); + + if (atomic_swap_uint(&track->lock, 1) != 0) + return false; + membar_enter(); + return true; } /* @@ -1661,9 +1668,10 @@ audio_track_lock_tryenter(audio_track_t *track) static __inline void audio_track_lock_enter(audio_track_t *track) { + /* Don't sleep here. */ while (audio_track_lock_tryenter(track) == false) - ; + SPINLOCK_BACKOFF_HOOK; } /* @@ -1672,7 +1680,8 @@ audio_track_lock_enter(audio_track_t *track) static __inline void audio_track_lock_exit(audio_track_t *track) { - atomic_swap_uint(&track->lock, 0); + + atomic_store_release(&track->lock, 0); } |
