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Subject[PATCH v3 23/23] tty: Add ldisc hangup debug messages
Date
Expected typical debug log:
[ 582.721965] tty_open: opening pts3...
[ 582.721970] tty_open: opening pts3...
[ 582.721977] tty_release: pts3 (tty count=3)...
[ 582.721980] tty_release: ptm3 (tty count=1)...
[ 582.722015] pts3 vhangup...
[ 582.722020] tty_ldisc_hangup: pts3: closing ldisc: ffff88007a920540
[ 582.724128] tty_release: pts3 (tty count=2)...
[ 582.724217] tty_ldisc_hangup: pts3: re-opened ldisc: ffff88007a920580
[ 582.724221] tty_release: ptm3: final close
[ 582.724234] tty_ldisc_release: ptm3: closing ldisc: ffff88007a920a80
[ 582.724238] tty_ldisc_release: ptm3: ldisc closed
[ 582.724241] tty_release: ptm3: freeing structure...
[ 582.724741] tty_open: opening pts3...

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/tty_ldisc.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 49e4825..7d3cab7 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -20,6 +20,17 @@
#include <linux/uaccess.h>
#include <linux/ratelimit.h>

+#undef LDISC_DEBUG_HANGUP
+
+#ifdef LDISC_DEBUG_HANGUP
+#define tty_ldisc_debug(tty, f, args...) ({ \
+ char __b[64]; \
+ printk(KERN_DEBUG "%s: %s: " f, __func__, tty_name(tty, __b), ##args); \
+})
+#else
+#define tty_ldisc_debug(tty, f, args...)
+#endif
+
/*
* This guards the refcounted line discipline lists. The lock
* must be taken with irqs off because there are hangup path
@@ -853,6 +864,8 @@ void tty_ldisc_hangup(struct tty_struct *tty)
int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
int err = 0;

+ tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc);
+
/*
* FIXME! What are the locking issues here? This may me overdoing
* things... This question is especially important now that we've
@@ -903,6 +916,8 @@ void tty_ldisc_hangup(struct tty_struct *tty)
mutex_unlock(&tty->ldisc_mutex);
if (reset)
tty_reset_termios(tty);
+
+ tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc);
}

/**
@@ -969,6 +984,8 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
* it does not race with the set_ldisc code path.
*/

+ tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc);
+
tty_ldisc_halt(tty, o_tty, NULL, NULL, MAX_SCHEDULE_TIMEOUT);

tty_lock_pair(tty, o_tty);
@@ -980,6 +997,8 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
tty_unlock_pair(tty, o_tty);
/* And the memory resources remaining (buffers, termios) will be
disposed of when the kref hits zero */
+
+ tty_ldisc_debug(tty, "ldisc closed\n");
}

/**
--
1.8.1.2


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