[PATCH 7/7] pty: Add debug message for ptmx open

From: Peter Hurley
Date: Sun Jul 12 2015 - 22:50:21 EST


Opens of /dev/ptmx don't use tty_open() so debug messages are
not printed for those opens; print a debug message with the
open count (which must always be 1) if TTY_DEBUG_HANGUP is defined.

NB: Each tty core source file undefs support for debug messages.
The relevant source file must be patched/edited to enable these
messages.

Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
drivers/tty/pty.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 4d5e840..4d5937c 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -26,6 +26,12 @@
#include <linux/mutex.h>
#include <linux/poll.h>

+#undef TTY_DEBUG_HANGUP
+#ifdef TTY_DEBUG_HANGUP
+# define tty_debug_hangup(tty, f, args...) tty_debug(tty, f, ##args)
+#else
+# define tty_debug_hangup(tty, f, args...) do {} while (0)
+#endif

#ifdef CONFIG_UNIX98_PTYS
static struct tty_driver *ptm_driver;
@@ -779,6 +785,8 @@ static int ptmx_open(struct inode *inode, struct file *filp)
if (retval)
goto err_release;

+ tty_debug_hangup(tty, "(tty count=%d)\n", tty->count);
+
tty_unlock(tty);
return 0;
err_release:
--
2.4.5

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