On 06/21/13 12:55, Arnd Bergmann wrote:
> __sync_fetch_and_and and __sync_fetch_and_or are functions that are provided
> by gcc and depending on the target architecture may be implemented in libgcc,
> which is not always available in the kernel. This leads to a build failure
> on ARMv5:
and on x86_64.
Acked-by: Randy Dunlap <rdun...@infradead.org>
Thanks.
>
> drivers/built-in.o: In function `line6_pcm_release':
> :(.text+0x3bfe80): undefined reference to `__sync_fetch_and_and_4'
> drivers/built-in.o: In function `line6_pcm_acquire':
> :(.text+0x3bff30): undefined reference to `__sync_fetch_and_or_4'
>
> To work around this, we can use the kernel-provided cmpxchg macro.
>
> Build-tested only.
>
> Signed-off-by: Arnd Bergmann <a...@arndb.de>
> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> Cc: Markus Grabner <grab...@icg.tugraz.at>
>
> diff --git a/drivers/staging/line6/pcm.c b/drivers/staging/line6/pcm.c
> index 02f77d7..4795f12 100644
> --- a/drivers/staging/line6/pcm.c
> +++ b/drivers/staging/line6/pcm.c
> @@ -107,11 +107,15 @@ static bool test_flags(unsigned long flags0, unsigned
> long flags1,
>
> int line6_pcm_acquire(struct snd_line6_pcm *line6pcm, int channels)
> {
> - unsigned long flags_old =
> - __sync_fetch_and_or(&line6pcm->flags, channels);
> - unsigned long flags_new = flags_old | channels;
> - unsigned long flags_final = flags_old;
> - int err = 0;
> + unsigned long flags_old, flags_new, flags_final;
> + int err;
> +
> + do {
> + flags_old = ACCESS_ONCE(line6pcm->flags);
> + flags_new = flags_old | channels;
> + } while (cmpxchg(&line6pcm->flags, flags_old, flags_new) != flags_old);
> +
> + flags_final = flags_old;
>
> line6pcm->prev_fbuf = NULL;
>
> @@ -197,9 +201,12 @@ pcm_acquire_error:
>
> int line6_pcm_release(struct snd_line6_pcm *line6pcm, int channels)
> {
> - unsigned long flags_old =
> - __sync_fetch_and_and(&line6pcm->flags, ~channels);
> - unsigned long flags_new = flags_old & ~channels;
> + unsigned long flags_old, flags_new;
> +
> + do {
> + flags_old = ACCESS_ONCE(line6pcm->flags);
> + flags_new = flags_old & ~channels;
> + } while (cmpxchg(&line6pcm->flags, flags_old, flags_new) != flags_old);
>
> if (test_flags(flags_new, flags_old, LINE6_BITS_CAPTURE_STREAM))
> line6_unlink_audio_in_urbs(line6pcm);
> --
--
~Randy
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