On Sun, Jan 26, 2014 at 03:44:14PM -0500, ido...@gmail.com wrote: > Hi misc@, > From http://marc.info/?l=openbsd-cvs&m=133217901415880&w=2 > > "The ``sleep until we have a writer'' behaviour of an open() on a fifo > does so with the file descriptor table locked, so if we are waiting for > another thread to be our writer we will hang forever. > > Found this using zotero and firefox." > > This behavior indeed hangs latest FF+Zotero. Is it fixable?
I've been running into this recently myself. What makes this worse, is that the process isn't even killable. Guenther tried to fix this, but it got backed out: http://anoncvs.estpak.ee/cgi-bin/cgit/openbsd-src/commit/?id=d8a387a9a09560b65562bc317ad63427bc9cb819 I was trying to look into this, but ran out of time :-( A workaround might be to patch either zotero or firefox, to open the fifo with O_RDWR instead of O_WRONLY. This way it won't block in open(). Here's my test program to trigger the issue. #include <err.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <pthread.h> #include <sys/types.h> void * open_thread(void *threadid) { int fd; sleep(1); /* delay to let main run into FIFO open first */ printf("before open in thread\n"); if ((fd = open("/tmp/regfile", O_CREAT| O_RDWR, 0600)) < 0) err(1, "open"); printf("after open in thread\n"); close(fd); pthread_exit(NULL); } int main(int argc, char** argv) { int fd; pthread_t thread; long t; if (pthread_create(&thread, NULL, open_thread, (void *)t) != 0) err(1, "pthread_create"); mkfifo("/tmp/block.fifo", 0600); printf("before blocking open in main\n"); if ((fd = open("/tmp/block.fifo", O_WRONLY)) < 0) err(1, "open"); printf("after blocking open in main\n"); close(fd); pthread_exit(NULL); exit(0); }
