From acf0330b0f5b1f4b8fc411cac45f57348b459525 Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Tue, 5 Jul 2016 15:51:23 +0200 Subject: run_erl: Fix failing run_erl invokation on OpenBSD Symptom: run_erl does exit(0) and child program (erl) does not seem to start. Running run_erl again however brings the previous child program to life. Problem: A race causing run_erl to read 0 from master pty and exit because the child has not yet opened its corresponding slave pty. Solution: Use the non standard openpty() function instead that does not expose this race as the slave fd is opened in the parent. Question: Is there a race free way to do this with posix_openpt on OpenBSD? --- erts/etc/unix/run_erl.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) (limited to 'erts/etc/unix') diff --git a/erts/etc/unix/run_erl.c b/erts/etc/unix/run_erl.c index d7cfbe675e..f8b5da47ab 100644 --- a/erts/etc/unix/run_erl.c +++ b/erts/etc/unix/run_erl.c @@ -904,14 +904,26 @@ static int create_fifo(char *name, int perm) * Find a master device, open and return fd and slave device name. */ +#ifdef HAVE_WORKING_POSIX_OPENPT + /* + * Use openpty() on OpenBSD even if we have posix_openpt() + * as there is a race when read from master pty returns 0 + * if child has not yet opened slave pty. + * (maybe other BSD's have the same problem?) + */ +# if !(defined(__OpenBSD__) && defined(HAVE_OPENPTY)) +# define TRY_POSIX_OPENPT +# endif +#endif + static int open_pty_master(char **ptyslave, int *sfdp) { int mfd; /* Use the posix_openpt if working, as this guarantees creation of the slave device properly. */ -#if defined(HAVE_WORKING_POSIX_OPENPT) || (defined(__sun) && defined(__SVR4)) -# ifdef HAVE_WORKING_POSIX_OPENPT +#if defined(TRY_POSIX_OPENPT) || (defined(__sun) && defined(__SVR4)) +# ifdef TRY_POSIX_OPENPT mfd = posix_openpt(O_RDWR); # elif defined(__sun) && defined(__SVR4) mfd = sf_open("/dev/ptmx", O_RDWR, 0); -- cgit v1.2.3