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Date: Sat, 09 Sep 2006 22:21:57 -0600
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Andrew Morton <akpm@...l.org>
Cc: <linux-kernel@...r.kernel.org>,
Linux Containers <containers@...ts.osdl.org>,
Oleg Nesterov <oleg@...sign.ru>,
Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: [PATCH] vt: Rework the console spawning variables.
This patch is against 2.6.18-rc6-mm1 with:
vt-update-spawnpid-to-be-a-struct-pid_t-tidy and
vt-update-spawnpid-to-be-a-struct-pid_t reverted. My previous version
of this patch did not correct the style that was already in use, and
failed to add proper SMP locking.
This is such a rare path it took me a while to figure out how to test
this after soring out the locking.
This patch does several things.
- The variables used are moved into a structure and declared in vt_kern.h
- A spinlock is added so we don't have SMP races updating the values.
- Instead of raw pid_t value a struct_pid is used to guard against
pid wrap around issues, if the daemon to spawn a new console dies.
Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
---
drivers/char/keyboard.c | 16 ++++++++++++----
drivers/char/vt_ioctl.c | 9 ++++++---
include/linux/vt_kern.h | 7 +++++++
3 files changed, 25 insertions(+), 7 deletions(-)
diff --git a/drivers/char/keyboard.c b/drivers/char/keyboard.c
index 3e90aac..99fb070 100644
--- a/drivers/char/keyboard.c
+++ b/drivers/char/keyboard.c
@@ -108,7 +108,11 @@ const int NR_TYPES = ARRAY_SIZE(max_vals
struct kbd_struct kbd_table[MAX_NR_CONSOLES];
static struct kbd_struct *kbd = kbd_table;
-int spawnpid, spawnsig;
+struct vt_spawn_console vt_spawn_con = {
+ .lock = SPIN_LOCK_UNLOCKED,
+ .pid = NULL,
+ .sig = 0,
+};
/*
* Variables exported for vt.c
@@ -578,9 +582,13 @@ static void fn_compose(struct vc_data *v
static void fn_spawn_con(struct vc_data *vc, struct pt_regs *regs)
{
- if (spawnpid)
- if (kill_proc(spawnpid, spawnsig, 1))
- spawnpid = 0;
+ spin_lock(&vt_spawn_con.lock);
+ if (vt_spawn_con.pid)
+ if (kill_pid(vt_spawn_con.pid, vt_spawn_con.sig, 1)) {
+ put_pid(vt_spawn_con.pid);
+ vt_spawn_con.pid = NULL;
+ }
+ spin_unlock(&vt_spawn_con.lock);
}
static void fn_SAK(struct vc_data *vc, struct pt_regs *regs)
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index a53e382..dc408af 100644
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -645,13 +645,16 @@ #endif
*/
case KDSIGACCEPT:
{
- extern int spawnpid, spawnsig;
if (!perm || !capable(CAP_KILL))
return -EPERM;
if (!valid_signal(arg) || arg < 1 || arg == SIGKILL)
return -EINVAL;
- spawnpid = current->pid;
- spawnsig = arg;
+
+ spin_lock_irq(&vt_spawn_con.lock);
+ put_pid(vt_spawn_con.pid);
+ vt_spawn_con.pid = get_pid(task_pid(current));
+ vt_spawn_con.sig = arg;
+ spin_unlock_irq(&vt_spawn_con.lock);
return 0;
}
diff --git a/include/linux/vt_kern.h b/include/linux/vt_kern.h
index 1009d3f..37a1a41 100644
--- a/include/linux/vt_kern.h
+++ b/include/linux/vt_kern.h
@@ -84,4 +84,11 @@ #define CON_BUF_SIZE (CONFIG_BASE_SMALL
extern char con_buf[CON_BUF_SIZE];
extern struct semaphore con_buf_sem;
+struct vt_spawn_console {
+ spinlock_t lock;
+ struct pid *pid;
+ int sig;
+};
+extern struct vt_spawn_console vt_spawn_con;
+
#endif /* _VT_KERN_H */
--
1.4.2.rc3.g7e18e-dirty
-
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