diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2014-02-10 05:59:04 +0400 |
|---|---|---|
| committer | Marcel Holtmann <marcel@holtmann.org> | 2014-02-15 01:39:29 +0400 |
| commit | c0fdfb80382e4901473ce0e31d1e7833c1d297be (patch) | |
| tree | d17f0af1f01f44f0ec3ba21169e18606845b95b1 | |
| parent | f87c24e74e88d767e7024c4464d0d1fb3642fb5e (diff) | |
| download | linux-c0fdfb80382e4901473ce0e31d1e7833c1d297be.tar.xz | |
tty: Fix ref counting for port krefs
The tty core supports two models for handling tty_port lifetimes;
the tty_port can use the kref supplied by tty_port (which will
automatically destruct the tty_port when the ref count drops to
zero) or it can destruct the tty_port manually.
For tty drivers that choose to use the port kref to manage the
tty_port lifetime, it is not possible to safely acquire a port
reference conditionally. If the last reference is released after
evaluating the condition but before acquiring the reference, a
bogus reference will be held while the tty_port destruction
commences.
Rather, only acquire a port reference if the ref count is non-zero
and allow the caller to distinguish if a reference has successfully
been acquired.
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-By: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
| -rw-r--r-- | include/linux/tty.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index 90b4fdc8a61f..4781d7b27dd3 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -518,9 +518,9 @@ extern void tty_port_put(struct tty_port *port); static inline struct tty_port *tty_port_get(struct tty_port *port) { - if (port) - kref_get(&port->kref); - return port; + if (port && kref_get_unless_zero(&port->kref)) + return port; + return NULL; } /* If the cts flow control is enabled, return true. */ |