linux-kernel - Re: [PATCH 3/8] module, jump

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Message-ID: <87egokjnv2.fsf@rustcorp.com.au>
Date:	Fri, 20 Mar 2015 14:56:25 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
	mathieu.desnoyers@...icios.com, oleg@...hat.com,
	paulmck@...ux.vnet.ibm.com, torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, andi@...stfloor.org,
	rostedt@...dmis.org, tglx@...utronix.de, peterz@...radead.org,
	Jason Baron <jbaron@...mai.com>
Subject: Re: [PATCH 3/8] module, jump_label: Fix module locking

Peter Zijlstra <peterz@...radead.org> writes:
> 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@...tcorp.com.au>
> Cc: Jason Baron <jbaron@...mai.com>
> Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  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;

Using __module_address() for this was just plain weird in the first
place.  How about:

        if (within_module(iter->key, mod))

Cheers,
Rusty.
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