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authorPeter Hurley <peter@hurleysoftware.com>2014-02-09 20:59:04 -0500
committerMarcel Holtmann <marcel@holtmann.org>2014-02-14 13:39:29 -0800
commitc0fdfb80382e4901473ce0e31d1e7833c1d297be (patch)
treed17f0af1f01f44f0ec3ba21169e18606845b95b1 /include/linux/tty.h
parentf87c24e74e88d767e7024c4464d0d1fb3642fb5e (diff)
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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>
Diffstat (limited to 'include/linux/tty.h')
-rw-r--r--include/linux/tty.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 90b4fdc..4781d7b 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. */
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