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authorLinus Torvalds <torvalds@linux-foundation.org>2011-06-03 17:33:24 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2011-06-03 17:33:24 -0400
commit55db4c64eddf37e31279ec15fe90314713bc9cfa (patch)
tree4bd186333049c5fcc1eacdff0efc82ac8b80ff5e /drivers/misc/ti-st
parent1fa7b6a29c61358cc2ca6f64cef4aa0e1a7ca74c (diff)
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 <benh@kernel.crashing.org> Reported-by: Milton Miller <miltonm@bga.com> Cc: Stefan Bigler <stefan.bigler@keymile.com> Cc: Toby Gray <toby.gray@realvnc.com> Cc: Felipe Balbi <balbi@ti.com> Cc: Greg Kroah-Hartman <gregkh@suse.de> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/misc/ti-st')
-rw-r--r--drivers/misc/ti-st/st_core.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/drivers/misc/ti-st/st_core.c b/drivers/misc/ti-st/st_core.c
index 1a05fe08e2cb..f91f82eabda7 100644
--- a/drivers/misc/ti-st/st_core.c
+++ b/drivers/misc/ti-st/st_core.c
@@ -747,8 +747,8 @@ static void st_tty_close(struct tty_struct *tty)
747 pr_debug("%s: done ", __func__); 747 pr_debug("%s: done ", __func__);
748} 748}
749 749
750static unsigned int st_tty_receive(struct tty_struct *tty, 750static void st_tty_receive(struct tty_struct *tty, const unsigned char *data,
751 const unsigned char *data, char *tty_flags, int count) 751 char *tty_flags, int count)
752{ 752{
753#ifdef VERBOSE 753#ifdef VERBOSE
754 print_hex_dump(KERN_DEBUG, ">in>", DUMP_PREFIX_NONE, 754 print_hex_dump(KERN_DEBUG, ">in>", DUMP_PREFIX_NONE,
@@ -761,8 +761,6 @@ static unsigned int st_tty_receive(struct tty_struct *tty,
761 */ 761 */
762 st_recv(tty->disc_data, data, count); 762 st_recv(tty->disc_data, data, count);
763 pr_debug("done %s", __func__); 763 pr_debug("done %s", __func__);
764
765 return count;
766} 764}
767 765
768/* wake-up function called in from the TTY layer 766/* wake-up function called in from the TTY layer