[PATCH v2 2/3] hvc_init(): Enforce one-time initialization.
From: Miche Baker-Harvey <hidden>
Date: 2011-11-08 19:30:22
Subsystem:
hypervisor virtual console driver, the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
hvc_init() must only be called once, and no thread should continue with hvc_alloc() until after initialization is complete. The original code does not enforce either of these requirements. A new mutex limits entry to hvc_init() to a single thread, and blocks all later comers until it has completed. This patch fixes multiple crash symptoms. Signed-off-by: Miche Baker-Harvey <redacted> --- drivers/tty/hvc/hvc_console.c | 13 +++++++++++-- 1 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index b6b2d18..09a6159 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c@@ -29,8 +29,9 @@ #include <linux/kernel.h> #include <linux/kthread.h> #include <linux/list.h> -#include <linux/module.h> #include <linux/major.h> +#include <linux/module.h> +#include <linux/mutex.h> #include <linux/sysrq.h> #include <linux/tty.h> #include <linux/tty_flip.h>
@@ -84,6 +85,10 @@ static LIST_HEAD(hvc_structs); * list traversal. */ static DEFINE_SPINLOCK(hvc_structs_lock); +/* + * only one task does allocation at a time. + */ +static DEFINE_MUTEX(hvc_ports_mutex); /* * This value is used to assign a tty->index value to a hvc_struct based
@@ -825,11 +830,15 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, int i; /* We wait until a driver actually comes along */ + mutex_lock(&hvc_ports_mutex); if (!hvc_driver) { int err = hvc_init(); - if (err) + if (err) { + mutex_unlock(&hvc_ports_mutex); return ERR_PTR(err); + } } + mutex_unlock(&hvc_ports_mutex); hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size, GFP_KERNEL);