From: Jason Baron <jbaron@redhat.com>
The sysrq code is taking a spinlock from both interrupt and process context
in an unsafe and deadlocky manner.
Move all those inlined functions out of sysrq.h, into sysrq.c then withdraw
all those exported-to-modules helper functions then remove
__sysrq_trylock_table() altogether and then use spin_lock_irqsave() in the
appropriate places.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/drivers/char/sysrq.c | 47 +++++++++++++++++++++++++++++-------------
25-akpm/include/linux/sysrq.h | 45 +---------------------------------------
2 files changed, 35 insertions(+), 57 deletions(-)
diff -puN drivers/char/sysrq.c~fix-altsysrq-deadlock drivers/char/sysrq.c
--- 25/drivers/char/sysrq.c~fix-altsysrq-deadlock Wed Oct 27 16:21:08 2004
+++ 25-akpm/drivers/char/sysrq.c Wed Oct 27 16:21:08 2004
@@ -315,14 +315,6 @@ static int sysrq_key_table_key2index(int
}
/*
- * table lock and unlocking functions, exposed to modules
- */
-
-void __sysrq_lock_table (void) { spin_lock(&sysrq_key_table_lock); }
-
-void __sysrq_unlock_table (void) { spin_unlock(&sysrq_key_table_lock); }
-
-/*
* get and put functions for the table, exposed to modules.
*/
@@ -354,8 +346,9 @@ void __handle_sysrq(int key, struct pt_r
struct sysrq_key_op *op_p;
int orig_log_level;
int i, j;
+ unsigned long flags;
- __sysrq_lock_table();
+ spin_lock_irqsave(&sysrq_key_table_lock, flags);
orig_log_level = console_loglevel;
console_loglevel = 7;
printk(KERN_INFO "SysRq : ");
@@ -377,7 +370,7 @@ void __handle_sysrq(int key, struct pt_r
printk ("\n");
console_loglevel = orig_log_level;
}
- __sysrq_unlock_table();
+ spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
}
/*
@@ -392,8 +385,34 @@ void handle_sysrq(int key, struct pt_reg
__handle_sysrq(key, pt_regs, tty);
}
+int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
+ struct sysrq_key_op *remove_op_p) {
+
+ int retval;
+ unsigned long flags;
+
+ spin_lock_irqsave(&sysrq_key_table_lock, flags);
+ if (__sysrq_get_key_op(key) == remove_op_p) {
+ __sysrq_put_key_op(key, insert_op_p);
+ retval = 0;
+ } else {
+ retval = -1;
+ }
+ spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
+
+ return retval;
+}
+
+int register_sysrq_key(int key, struct sysrq_key_op *op_p)
+{
+ return __sysrq_swap_key_ops(key, op_p, NULL);
+}
+
+int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
+{
+ return __sysrq_swap_key_ops(key, NULL, op_p);
+}
+
EXPORT_SYMBOL(handle_sysrq);
-EXPORT_SYMBOL(__sysrq_lock_table);
-EXPORT_SYMBOL(__sysrq_unlock_table);
-EXPORT_SYMBOL(__sysrq_get_key_op);
-EXPORT_SYMBOL(__sysrq_put_key_op);
+EXPORT_SYMBOL(register_sysrq_key);
+EXPORT_SYMBOL(unregister_sysrq_key);
diff -puN include/linux/sysrq.h~fix-altsysrq-deadlock include/linux/sysrq.h
--- 25/include/linux/sysrq.h~fix-altsysrq-deadlock Wed Oct 27 16:21:08 2004
+++ 25-akpm/include/linux/sysrq.h Wed Oct 27 16:21:08 2004
@@ -31,49 +31,8 @@ struct sysrq_key_op {
void handle_sysrq(int, struct pt_regs *, struct tty_struct *);
void __handle_sysrq(int, struct pt_regs *, struct tty_struct *);
-
-/*
- * Sysrq registration manipulation functions
- */
-
-void __sysrq_lock_table (void);
-void __sysrq_unlock_table (void);
-struct sysrq_key_op *__sysrq_get_key_op (int key);
-void __sysrq_put_key_op (int key, struct sysrq_key_op *op_p);
-
-extern __inline__ int
-__sysrq_swap_key_ops_nolock(int key, struct sysrq_key_op *insert_op_p,
- struct sysrq_key_op *remove_op_p)
-{
- int retval;
- if (__sysrq_get_key_op(key) == remove_op_p) {
- __sysrq_put_key_op(key, insert_op_p);
- retval = 0;
- } else {
- retval = -1;
- }
- return retval;
-}
-
-extern __inline__ int
-__sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
- struct sysrq_key_op *remove_op_p) {
- int retval;
- __sysrq_lock_table();
- retval = __sysrq_swap_key_ops_nolock(key, insert_op_p, remove_op_p);
- __sysrq_unlock_table();
- return retval;
-}
-
-static inline int register_sysrq_key(int key, struct sysrq_key_op *op_p)
-{
- return __sysrq_swap_key_ops(key, op_p, NULL);
-}
-
-static inline int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
-{
- return __sysrq_swap_key_ops(key, NULL, op_p);
-}
+int register_sysrq_key(int, struct sysrq_key_op *);
+int unregister_sysrq_key(int, struct sysrq_key_op *);
#else
_