Re: [RFC][PATCH 4/9] module, jump_label: Fix module locking

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Sat, Feb 28, 2015 at 10:24:51PM +0100, Peter Zijlstra wrote:
> As per the module core lockdep annotations:
> 
> [   18.034047] ---[ end trace 9294429076a9c673 ]---
> [   18.047760] Hardware name: Intel Corporation S2600GZ/S2600GZ, BIOS SE5C600.86B.02.02.0002.122320131210 12/23/2013
> [   18.059228]  ffffffff817d8676 ffff880036683c38 ffffffff8157e98b 0000000000000001
> [   18.067541]  0000000000000000 ffff880036683c78 ffffffff8105fbc7 ffff880036683c68
> [   18.075851]  ffffffffa0046b08 0000000000000000 ffffffffa0046d00 ffffffffa0046cc8
> [   18.084173] Call Trace:
> [   18.086906]  [<ffffffff8157e98b>] dump_stack+0x4f/0x7b
> [   18.092649]  [<ffffffff8105fbc7>] warn_slowpath_common+0x97/0xe0
> [   18.099361]  [<ffffffff8105fc2a>] warn_slowpath_null+0x1a/0x20
> [   18.105880]  [<ffffffff810ee502>] __module_address+0x1d2/0x1e0
> [   18.112400]  [<ffffffff81161153>] jump_label_module_notify+0x143/0x1e0
> [   18.119710]  [<ffffffff810814bf>] notifier_call_chain+0x4f/0x70
> [   18.126326]  [<ffffffff8108160e>] __blocking_notifier_call_chain+0x5e/0x90
> [   18.134009]  [<ffffffff81081656>] blocking_notifier_call_chain+0x16/0x20
> [   18.141490]  [<ffffffff810f0f00>] load_module+0x1b50/0x2660
> [   18.147720]  [<ffffffff810f1ade>] SyS_init_module+0xce/0x100
> [   18.154045]  [<ffffffff81587429>] system_call_fastpath+0x12/0x17
> [   18.160748] ---[ end trace 9294429076a9c674 ]---
> 
> Jump labels is not doing it right; fix this.
> 
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Jason Baron <jbaron@akamai.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> ---
>  kernel/jump_label.c |   21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -280,6 +280,17 @@ void jump_label_apply_nops(struct module
>  	}
>  }
> 
> +static inline bool address_in_module(unsigned long addr, struct module *mod)
> +{
> +	bool ret;
> +
> +	preempt_disable();
> +	ret = __module_address(addr) == mod;
> +	preempt_enable();
> +
> +	return ret;
> +}
> +
>  static int jump_label_add_module(struct module *mod)
>  {
>  	struct jump_entry *iter_start = mod->jump_entries;
> @@ -302,7 +313,7 @@ static int jump_label_add_module(struct
>  			continue;
> 
>  		key = iterk;
> -		if (__module_address(iter->key) == mod) {
> +		if (address_in_module(iter->key, mod)) {
>  			/*
>  			 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
>  			 */
> @@ -339,7 +350,7 @@ static void jump_label_del_module(struct
> 
>  		key = (struct static_key *)(unsigned long)iter->key;
> 
> -		if (__module_address(iter->key) == mod)
> +		if (address_in_module(iter->key, mod))
>  			continue;
> 
>  		prev = &key->next;
> @@ -443,14 +454,16 @@ static void jump_label_update(struct sta
>  {
>  	struct jump_entry *stop = __stop___jump_table;
>  	struct jump_entry *entry = jump_label_get_entries(key);
> -
>  #ifdef CONFIG_MODULES
> -	struct module *mod = __module_address((unsigned long)key);
> +	struct module *mod;
> 
>  	__jump_label_mod_update(key, enable);
> 
> +	preempt_disable();
> +	mod = __module_address((unsigned long)key);
>  	if (mod)
>  		stop = mod->jump_entries + mod->num_jump_entries;
> +	preempt_enable();
>  #endif
>  	/* if there are no users, entry can be NULL */
>  	if (entry)
> 
>