fftw hangs on raspberry pi3

[soundart]

Currently fftw does not work on my raspberry pi3. It hangs in a loop doing calls to clock_gettime:

clock_gettime(CLOCK_SGI_CYCLE, 0x7ea42558) = -1 EINVAL (Invalid argument)
clock_gettime(CLOCK_SGI_CYCLE, 0x7ea42558) = -1 EINVAL (Invalid argument)
clock_gettime(CLOCK_REALTIME, {tv_sec=1513978172, tv_nsec=339522337}) = 0
clock_gettime(CLOCK_REALTIME, {tv_sec=1513978172, tv_nsec=339672025}) = 0
clock_gettime(CLOCK_SGI_CYCLE, 0x7ea42558) = -1 EINVAL (Invalid argument)

The call clock_gettime(CLOCK_SGI_CYCLE, &t) from function getticks() fails with EINVAL.
See : http://elixir.free-electrons.com/linux/latest/source/include/uapi/linux/time.h#L62 - "The driver implementing this got removed. The clock ID is kept as a place holder. Do not reuse!"

There was a commit preventing the usage of CLOCK_SGI_CYCLE on ANDROID. It should probably not be used on plain linux too.

I discussed this here: 950b153

I will add a pull request based on https://github.com/SETIguy comment 950b153#commitcomment-26583436

[soundart]

See #123

[paigeadelethompson]

Yeah Im having this issue too now myself, how is it that I am the only person who is though ???? This should be a pretty big deal by my account (cant start either gqrx nor sdrangel) Am I understanding correctly that nobody actually uses these on Raspi ????

#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_SGI_CYCLE) && !defined(HAVE_TICK_COUNTER) && !defined(__ANDROID__)
typedef struct timespec ticks;

static inline ticks getticks(void)
{
     struct timespec t;
     clock_gettime(CLOCK_SGI_CYCLE, &t);
     return t;
}