From d79a580936396bbcd2f4fae2c6215f9cf81e3c0d Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Sat, 10 Feb 2007 01:43:52 -0800 Subject: [PATCH] uml: console locking fixes Clean up the console driver locking. There are various problems here, including sleeping under a spinlock and spinlock recursion, some of which are fixed here. This patch deals with the locking involved with opens and closes. The problem is that an mconsole request to change a console's configuration can race with an open. Changing a configuration should only be done when a console isn't opened. Also, an open must be looking at a stable configuration. In addition, a get configuration request must observe the same locking since it must also see a stable configuration. With the old locking, it was possible for this to hang indefinitely in some cases because open would block for a long time waiting for a connection from the host while holding the lock needed by the mconsole request. As explained in the long comment, this is fixed by adding a spinlock for the use count and configuration and a mutex for the actual open and close. Signed-off-by: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/include/line.h | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) (limited to 'arch/um/include/line.h') diff --git a/arch/um/include/line.h b/arch/um/include/line.h index 5f232ae89fbb..b79643eeee08 100644 --- a/arch/um/include/line.h +++ b/arch/um/include/line.h @@ -11,6 +11,7 @@ #include "linux/tty.h" #include "linux/interrupt.h" #include "linux/spinlock.h" +#include "linux/mutex.h" #include "chan_user.h" #include "mconsole_kern.h" @@ -32,15 +33,17 @@ struct line_driver { struct line { struct tty_struct *tty; + spinlock_t count_lock; + int valid; + + struct mutex open_mutex; char *init_str; int init_pri; struct list_head chan_list; - int valid; - int count; - int throttled; + /*This lock is actually, mostly, local to*/ spinlock_t lock; - + int throttled; /* Yes, this is a real circular buffer. * XXX: And this should become a struct kfifo! * @@ -57,7 +60,8 @@ struct line { }; #define LINE_INIT(str, d) \ - { .init_str = str, \ + { .count_lock = SPIN_LOCK_UNLOCKED, \ + .init_str = str, \ .init_pri = INIT_STATIC, \ .valid = 1, \ .lock = SPIN_LOCK_UNLOCKED, \ -- cgit