Traditionally, many of ALSA library functions are supposed to be
thread-unsafe, and applications are required to take care of thread
safety by themselves. However, people never be careful enough, and
almost all applications fail in this regard.
This patch is an attempt to harden the thread safety in exported PCM
functions in a simplistic way: just wrap some of exported functions
with the pthread mutex of each PCM object. Not all API functions are
wrapped by the mutex since it doesn't make sense. Instead, the
patchset covers only the functions that may be likely called
concurrently. The supposedly thread-safe API functions are marked in
the document.
For achieving the feature, two new fields are added snd_pcm_t when the
option is enabled: thread_safe and lock. The former indicates that
the plugin is thread-safe that doesn't need this workaround and the
latter is the pthread mutex. Currently only hw plugin have
thread_safe=1. So, the most of real-time sensitive apps won't be
influenced by this patchset.
Although the patch covers most of PCM ops, a few snd_pcm_fast_ops are
left without the extra mutex locking: namely, the ones that may have
blocking behavior, i.e. resume, drain, readi, writei, readn and
writen. These are supposed to handle own locking in the callbacks.
Also, if anyone wants to disable this new thread-safe API feature, it
can be still turned off via --disable-thread-safety configure option.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Some systems, like Android/Bionic, do not support SysV at all.
Let the configure script detect if the header is available, and
if not, automatically disable the pieces that require it.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
If you build with --disable-pcm, the rawmidi code fails to link because
it uses the page_size helper declared in local.h, but the page_* funcs
are in the pcm mmap module. Move these funcs into conf.c so that they
are always available to the rest of the system.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
A missing "break" in procedure snd_pcm_write_mmap() causes
execution of "case SND_PCM_ACCESS_MMAP_NONINTERLEAVED" to
fall through next "default" case of the "switch" statement.
Since "default" handles error cases, the procedure returns
error.
The error fixed by this patch blocks transfer of capture
data from kernel to application. Execution get stuck in
alsa-lib, that discards all received data.
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
The mmap_channels and running_areas fields are allocated using calloc, but
are not freed on an error path.
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Suman Saha <sumsaha@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
The previous code did not allocated a separate buffer for all channels
when a NONINTERLEAVED access was used. The result was that only one
"shared" buffer was incorrectly allocated.
Also, the code was a bit cleaned (cosmetic change only).
Fixed the bug producing silent tones with some combinations of plugins.
The internal buffer handling is now better (cleaner) integrated with
snd_pcm_generic_*().
Add snd_pcm_hw_params_get/set_export_buffer() API functions.
They control to ensure the buffer export to other processes.
If this flag is set, the local buffer of a plugin is exported over IPC shm.
Otherwise the buffer can be handled only locally (no shm).
Also fixed Version file for 1.0.9.
Change the handling of non-fatal errors. Now the non-fatal error
messages are not shown in stderr and no assert() as default. The
behavior can be changed with LIBASOUND_DEBUG environment variable.
Added undo callbacks for snd_pcm_plugin based plugins.
- helpers when mmap_commit proceed only a partial transfer
Fixes to avail_update implementation in pcm_hw.c.
