3.8-stable patches

added patches:
	tty-don-t-deadlock-while-flushing-workqueue.patch

diff --git a/queue-3.8/series b/queue-3.8/series
index 64b4ae53ca28b98ebb09d34a04672d6678e04e12..14490542cc6f6969ba317228deddae221b19c25f 100644 (file)
--- a/queue-3.8/series
+++ b/queue-3.8/series
@@ -24,3 +24,4 @@ ftrace-move-ftrace_filter_lseek-out-of-config_dynamic_ftrace-section.patch
 sched_clock-prevent-64bit-inatomicity-on-32bit-systems.patch
 x86-mm-paravirt-fix-vmalloc_fault-oops-during-lazy-mmu-updates.patch
 x86-mm-patch-out-arch_flush_lazy_mmu_mode-when-running-on-bare-metal.patch
+tty-don-t-deadlock-while-flushing-workqueue.patch

diff --git a/queue-3.8/tty-don-t-deadlock-while-flushing-workqueue.patch b/queue-3.8/tty-don-t-deadlock-while-flushing-workqueue.patch
new file mode 100644 (file)
index 0000000..86c05dd
--- /dev/null
+++ b/queue-3.8/tty-don-t-deadlock-while-flushing-workqueue.patch
@@ -0,0 +1,142 @@
+From 852e4a8152b427c3f318bb0e1b5e938d64dcdc32 Mon Sep 17 00:00:00 2001
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Tue, 25 Dec 2012 23:02:48 +0100
+Subject: tty: don't deadlock while flushing workqueue
+
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+
+commit 852e4a8152b427c3f318bb0e1b5e938d64dcdc32 upstream.
+
+Since commit 89c8d91e31f2 ("tty: localise the lock") I see a dead lock
+in one of my dummy_hcd + g_nokia test cases. The first run was usually
+okay, the second often resulted in a splat by lockdep and the third was
+usually a dead lock.
+Lockdep complained about tty->hangup_work and tty->legacy_mutex taken
+both ways:
+| ======================================================
+| [ INFO: possible circular locking dependency detected ]
+| 3.7.0-rc6+ #204 Not tainted
+| -------------------------------------------------------
+| kworker/2:1/35 is trying to acquire lock:
+|  (&tty->legacy_mutex){+.+.+.}, at: [<c14051e6>] tty_lock_nested+0x36/0x80
+|
+| but task is already holding lock:
+|  ((&tty->hangup_work)){+.+...}, at: [<c104f6e4>] process_one_work+0x124/0x5e0
+|
+| which lock already depends on the new lock.
+|
+| the existing dependency chain (in reverse order) is:
+|
+| -> #2 ((&tty->hangup_work)){+.+...}:
+|        [<c107fe74>] lock_acquire+0x84/0x190
+|        [<c104d82d>] flush_work+0x3d/0x240
+|        [<c12e6986>] tty_ldisc_flush_works+0x16/0x30
+|        [<c12e7861>] tty_ldisc_release+0x21/0x70
+|        [<c12e0dfc>] tty_release+0x35c/0x470
+|        [<c1105e28>] __fput+0xd8/0x270
+|        [<c1105fcd>] ____fput+0xd/0x10
+|        [<c1051dd9>] task_work_run+0xb9/0xf0
+|        [<c1002a51>] do_notify_resume+0x51/0x80
+|        [<c140550a>] work_notifysig+0x35/0x3b
+|
+| -> #1 (&tty->legacy_mutex/1){+.+...}:
+|        [<c107fe74>] lock_acquire+0x84/0x190
+|        [<c140276c>] mutex_lock_nested+0x6c/0x2f0
+|        [<c14051e6>] tty_lock_nested+0x36/0x80
+|        [<c1405279>] tty_lock_pair+0x29/0x70
+|        [<c12e0bb8>] tty_release+0x118/0x470
+|        [<c1105e28>] __fput+0xd8/0x270
+|        [<c1105fcd>] ____fput+0xd/0x10
+|        [<c1051dd9>] task_work_run+0xb9/0xf0
+|        [<c1002a51>] do_notify_resume+0x51/0x80
+|        [<c140550a>] work_notifysig+0x35/0x3b
+|
+| -> #0 (&tty->legacy_mutex){+.+.+.}:
+|        [<c107f3c9>] __lock_acquire+0x1189/0x16a0
+|        [<c107fe74>] lock_acquire+0x84/0x190
+|        [<c140276c>] mutex_lock_nested+0x6c/0x2f0
+|        [<c14051e6>] tty_lock_nested+0x36/0x80
+|        [<c140523f>] tty_lock+0xf/0x20
+|        [<c12df8e4>] __tty_hangup+0x54/0x410
+|        [<c12dfcb2>] do_tty_hangup+0x12/0x20
+|        [<c104f763>] process_one_work+0x1a3/0x5e0
+|        [<c104fec9>] worker_thread+0x119/0x3a0
+|        [<c1055084>] kthread+0x94/0xa0
+|        [<c140ca37>] ret_from_kernel_thread+0x1b/0x28
+|
+|other info that might help us debug this:
+|
+|Chain exists of:
+|  &tty->legacy_mutex --> &tty->legacy_mutex/1 --> (&tty->hangup_work)
+|
+| Possible unsafe locking scenario:
+|
+|       CPU0                    CPU1
+|       ----                    ----
+|  lock((&tty->hangup_work));
+|                               lock(&tty->legacy_mutex/1);
+|                               lock((&tty->hangup_work));
+|  lock(&tty->legacy_mutex);
+|
+| *** DEADLOCK ***
+
+Before the path mentioned tty_ldisc_release() look like this:
+
+|      tty_ldisc_halt(tty);
+|      tty_ldisc_flush_works(tty);
+|      tty_lock();
+
+As it can be seen, it first flushes the workqueue and then grabs the
+tty_lock. Now we grab the lock first:
+
+|      tty_lock_pair(tty, o_tty);
+|      tty_ldisc_halt(tty);
+|      tty_ldisc_flush_works(tty);
+
+so lockdep's complaint seems valid.
+
+The earlier version of this patch took the ldisc_mutex since the other
+user of tty_ldisc_flush_works() (tty_set_ldisc()) did this.
+Peter Hurley then said that it is should not be requried. Since it
+wasn't done earlier, I dropped this part.
+The code under tty_ldisc_kill() was executed earlier with the tty lock
+taken so it is taken again.
+
+I was able to reproduce the deadlock on v3.8-rc1, this patch fixes the
+problem in my testcase. I didn't notice any problems so far.
+
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Cc: Alan Cox <alan@linux.intel.com>
+Cc: Peter Hurley <peter@hurleysoftware.com>
+Cc: Bryan O'Donoghue <bryan.odonoghue.lkml@nexus-software.ie>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ drivers/tty/tty_ldisc.c |   10 +++++-----
+ 1 file changed, 5 insertions(+), 5 deletions(-)
+
+--- a/drivers/tty/tty_ldisc.c
++++ b/drivers/tty/tty_ldisc.c
+@@ -934,17 +934,17 @@ void tty_ldisc_release(struct tty_struct
+        * race with the set_ldisc code path.
+        */
+ 
+-      tty_lock_pair(tty, o_tty);
+       tty_ldisc_halt(tty);
+-      tty_ldisc_flush_works(tty);
+-      if (o_tty) {
++      if (o_tty)
+               tty_ldisc_halt(o_tty);
++
++      tty_ldisc_flush_works(tty);
++      if (o_tty)
+               tty_ldisc_flush_works(o_tty);
+-      }
+ 
++      tty_lock_pair(tty, o_tty);
+       /* This will need doing differently if we need to lock */
+       tty_ldisc_kill(tty);
+-
+       if (o_tty)
+               tty_ldisc_kill(o_tty);
+