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authorAndy Wingo <wingo@pobox.com>2013-01-17 12:38:56 +0100
committerAndy Wingo <wingo@pobox.com>2013-01-17 12:38:56 +0100
commita796d0a95442b379a9ff2cdf9e0eb6efccc5dc08 (patch)
tree05142a024acdb1691f7617293cf1da92ddfd3ae3 /libguile/posix.c
parent36c210d14e8572939901b9251492a3f4bf94988c (diff)
downloadguile-a796d0a95442b379a9ff2cdf9e0eb6efccc5dc08.tar.gz
warn on multithreaded fork
* libguile/posix.c (scm_fork): Issue a warning on a multithreaded fork. * doc/ref/posix.texi (Processes): Add note about multithreaded fork. * test-suite/tests/00-socket.test: Moved here, from socket.test, so as to run before any threads are created. * test-suite/Makefile.am: Adapt.
Diffstat (limited to 'libguile/posix.c')
-rw-r--r--libguile/posix.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/libguile/posix.c b/libguile/posix.c
index 4d5fdcf96..324f21b78 100644
--- a/libguile/posix.c
+++ b/libguile/posix.c
@@ -1249,6 +1249,22 @@ SCM_DEFINE (scm_fork, "primitive-fork", 0, 0, 0,
#define FUNC_NAME s_scm_fork
{
int pid;
+ if (scm_ilength (scm_all_threads ()) != 1)
+ /* Other threads may be holding on to resources that Guile needs --
+ it is not safe to permit one thread to fork while others are
+ running.
+
+ In addition, POSIX clearly specifies that if a multi-threaded
+ program forks, the child must only call functions that are
+ async-signal-safe. We can't guarantee that in general. The best
+ we can do is to allow forking only very early, before any call to
+ sigaction spawns the signal-handling thread. */
+ scm_display
+ (scm_from_latin1_string
+ ("warning: call to primitive-fork while multiple threads are running;\n"
+ " further behavior unspecified. See \"Processes\" in the\n"
+ " manual, for more information.\n"),
+ scm_current_warning_port ());
pid = fork ();
if (pid == -1)
SCM_SYSERROR;