On Sat, Jan 30, 2021, 1:58 PM Gregory Nutt <spudan...@gmail.com> wrote:
> > I'm thinking again about this. Why wouldn't it be possible to make > functions > > using SIGEV_THREAD (such as timer_settime) create a pthread behind > > the scenes (only the first time a SIGEV_THREAD is setup)? The underlying > > watchdog would go to a handler that posts a semaphore/condition variable > > that the helper thread is waiting on. When this thread unblocks, it > calls the > > user handler directly. > > > > The thread would be created per-process in KERNEL mode, so that shouldn't > > be a problem (inside same address space as user handler). I suspect the > > unblocking of the thread should also be possible in multi-process somehow > > (named semaphore?). > > > > This is essentially what I'm doing myself around a call to timer_settime. > > > > Best, > > Matias > > I think a proper approach would be to see how Linux/GLIBC accomplish > this. I think that would give you some ideas for proper implementation. > This is actually fairly in line with how the Musl libc implements this (at least from a quick look). There are a few important details in there, but it looks quite clean. http://git.musl-libc.org/cgit/musl/tree/src/time/timer_create.c While Musl is usually not as fast as glibc, I find the implementations usually more straight forward and smaller code size. >
