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authorJiri Slaby <jslaby@suse.cz>2012-03-05 14:51:56 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-03-08 11:38:51 -0800
commit26b23209c0ea5503824df60b8f218fb04b80cad0 (patch)
tree6225f9e7e4db8dc77023887e8e70539f8b185396
parent91cedcde1e5feede6c1e4c2086ec4f3c84c56d4f (diff)
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TTY: tty_driver, document tty->ops->shutdown limitation
Note that tty->ops->shutdown is called from whatever context the user drops the last tty reference from. E.g. if one takes a reference in an ISR, tty close happens on other CPU and the final tty put is from the ISR, tty->ops->shutdown will be called from that hard irq context. We would have a problem in vt if we start using tty refcounting from other contexts than user there. It is because vt's shutdown uses mutexes. This is yet to be fixed. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Reported-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--include/linux/tty_driver.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index e064f1704e20..6e6dbb7447b6 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -50,6 +50,8 @@
* Note that tty_shutdown() is not called if ops->shutdown is defined.
* This means one is responsible to take care of calling ops->remove (e.g.
* via tty_driver_remove_tty) and releasing tty->termios.
+ * Note that this hook may be called from *all* the contexts where one
+ * uses tty refcounting (e.g. tty_port_tty_get).
*
*
* void (*cleanup)(struct tty_struct * tty);