From: Paolo 'Blaisorblade' Giarrusso , Chris Wedgwood If UML wants to open an xterm channel and the xterm does not run properly (eg. terminates soon after starting) we will get a hang (a comment added in the patch explains why). This avoids the most common cause for this and adds a comment (which long term will go away with a rewrite of that code); the complete fix would be to catch the xterm process dying, up(&data->sem), and -EIO all requests from that point onwards. That applies for some of the other channels too, so part of the code should probably be abstracted a little and generalized. Signed-off-by: Chris Wedgwood Signed-off-by: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton --- 25-akpm/arch/um/drivers/xterm.c | 7 +++++++ 25-akpm/arch/um/drivers/xterm_kern.c | 9 ++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff -puN arch/um/drivers/xterm.c~uml-fail-xterm_open-when-we-have-no-display arch/um/drivers/xterm.c --- 25/arch/um/drivers/xterm.c~uml-fail-xterm_open-when-we-have-no-display Thu Jan 13 15:27:10 2005 +++ 25-akpm/arch/um/drivers/xterm.c Thu Jan 13 15:27:10 2005 @@ -97,6 +97,13 @@ int xterm_open(int input, int output, in if(os_access(argv[4], OS_ACC_X_OK) < 0) argv[4] = "port-helper"; + /* Check that DISPLAY is set, this doesn't guarantee the xterm + * will work but w/o it we can be pretty sure it won't. */ + if (!getenv("DISPLAY")) { + printk("xterm_open: $DISPLAY not set.\n"); + return -ENODEV; + } + fd = mkstemp(file); if(fd < 0){ printk("xterm_open : mkstemp failed, errno = %d\n", errno); diff -puN arch/um/drivers/xterm_kern.c~uml-fail-xterm_open-when-we-have-no-display arch/um/drivers/xterm_kern.c --- 25/arch/um/drivers/xterm_kern.c~uml-fail-xterm_open-when-we-have-no-display Thu Jan 13 15:27:10 2005 +++ 25-akpm/arch/um/drivers/xterm_kern.c Thu Jan 13 15:27:10 2005 @@ -46,6 +46,8 @@ int xterm_fd(int socket, int *pid_out) printk(KERN_ERR "xterm_fd : failed to allocate xterm_wait\n"); return(-ENOMEM); } + + /* This is a locked semaphore... */ *data = ((struct xterm_wait) { .sem = __SEMAPHORE_INITIALIZER(data->sem, 0), .fd = socket, @@ -55,12 +57,17 @@ int xterm_fd(int socket, int *pid_out) err = um_request_irq(XTERM_IRQ, socket, IRQ_READ, xterm_interrupt, SA_INTERRUPT | SA_SHIRQ | SA_SAMPLE_RANDOM, "xterm", data); - if(err){ + if (err){ printk(KERN_ERR "xterm_fd : failed to get IRQ for xterm, " "err = %d\n", err); ret = err; goto out; } + + /* ... so here we wait for an xterm interrupt. + * + * XXX Note, if the xterm doesn't work for some reason (eg. DISPLAY + * isn't set) this will hang... */ down(&data->sem); free_irq_by_irq_and_dev(XTERM_IRQ, data); _