From 55db4c64eddf37e31279ec15fe90314713bc9cfa Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sat, 4 Jun 2011 06:33:24 +0900 Subject: Revert "tty: make receive_buf() return the amout of bytes received" This reverts commit b1c43f82c5aa265442f82dba31ce985ebb7aa71c. It was broken in so many ways, and results in random odd pty issues. It re-introduced the buggy schedule_work() in flush_to_ldisc() that can cause endless work-loops (see commit a5660b41af6a: "tty: fix endless work loop when the buffer fills up"). It also used an "unsigned int" return value fo the ->receive_buf() function, but then made multiple functions return a negative error code, and didn't actually check for the error in the caller. And it didn't actually work at all. BenH bisected down odd tty behavior to it: "It looks like the patch is causing some major malfunctions of the X server for me, possibly related to PTYs. For example, cat'ing a large file in a gnome terminal hangs the kernel for -minutes- in a loop of what looks like flush_to_ldisc/workqueue code, (some ftrace data in the quoted bits further down). ... Some more data: It -looks- like what happens is that the flush_to_ldisc work queue entry constantly re-queues itself (because the PTY is full ?) and the workqueue thread will basically loop forver calling it without ever scheduling, thus starving the consumer process that could have emptied the PTY." which is pretty much exactly the problem we fixed in a5660b41af6a. Milton Miller pointed out the 'unsigned int' issue. Reported-by: Benjamin Herrenschmidt Reported-by: Milton Miller Cc: Stefan Bigler Cc: Toby Gray Cc: Felipe Balbi Cc: Greg Kroah-Hartman Cc: Alan Cox Signed-off-by: Linus Torvalds --- drivers/isdn/gigaset/ser-gigaset.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) (limited to 'drivers/isdn') diff --git a/drivers/isdn/gigaset/ser-gigaset.c b/drivers/isdn/gigaset/ser-gigaset.c index 1d44d470897c..86a5c4f7775e 100644 --- a/drivers/isdn/gigaset/ser-gigaset.c +++ b/drivers/isdn/gigaset/ser-gigaset.c @@ -674,7 +674,7 @@ gigaset_tty_ioctl(struct tty_struct *tty, struct file *file, * cflags buffer containing error flags for received characters (ignored) * count number of received characters */ -static unsigned int +static void gigaset_tty_receive(struct tty_struct *tty, const unsigned char *buf, char *cflags, int count) { @@ -683,12 +683,12 @@ gigaset_tty_receive(struct tty_struct *tty, const unsigned char *buf, struct inbuf_t *inbuf; if (!cs) - return -ENODEV; + return; inbuf = cs->inbuf; if (!inbuf) { dev_err(cs->dev, "%s: no inbuf\n", __func__); cs_put(cs); - return -EINVAL; + return; } tail = inbuf->tail; @@ -725,8 +725,6 @@ gigaset_tty_receive(struct tty_struct *tty, const unsigned char *buf, gig_dbg(DEBUG_INTR, "%s-->BH", __func__); gigaset_schedule_event(cs); cs_put(cs); - - return count; } /* -- cgit v1.2.3