bug#49682: 27.2.50; accept-process-output within accept-process-output hangs emacs

[Dmitry Gutov]

On 26.07.2021 23:55, Rajeev N wrote:
> I am able to reproduce the hang on head of master and emacs-27 branches using 
> emacs -Q,  it does not happen every time, sometime it takes a few tries.  The 
> following is what is shown by strace in a loop:
>
> pselect6(20, [3 5 13 17 19], NULL, NULL, {tv_sec=0, tv_nsec=0}, {NULL, 8}) = 1 
> (in [19], left {tv_sec=0, tv_nsec=0})
> rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0
> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0
> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> pselect6(20, [3 5 6 8 13 15 17 19], [], NULL, {tv_sec=0, tv_nsec=0}, {NULL, 8}) 
> = 1 (in [19], left {tv_sec=0, tv_nsec=0})
> rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0
> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0
> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> pselect6(20, [3 5 13 17 19], NULL, NULL, {tv_sec=0, tv_nsec=0}, {NULL, 8}) = 1 
> (in [19], left {tv_sec=0, tv_nsec=0})
> rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0
> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0
> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> pselect6(20, [3 5 6 8 13 15 17 19], [], NULL, {tv_sec=0, tv_nsec=0}, {NULL, 8}) 
> = 1 (in [19], left {tv_sec=0, tv_nsec=0})
> rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0
> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0

Maybe Lars or Eli can interpret this log.