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Commit cf0a2543 authored by Yang Shi's avatar Yang Shi Committed by Catalin Marinas
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arm64: replace read_lock to rcu lock in call_step_hook 



BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917
in_atomic(): 1, irqs_disabled(): 128, pid: 383, name: sh
Preemption disabled at:[<ffff800000124c18>] kgdb_cpu_enter+0x158/0x6b8

CPU: 3 PID: 383 Comm: sh Tainted: G        W       4.1.13-rt13 #2
Hardware name: Freescale Layerscape 2085a RDB Board (DT)
Call trace:
[<ffff8000000885e8>] dump_backtrace+0x0/0x128
[<ffff800000088734>] show_stack+0x24/0x30
[<ffff80000079a7c4>] dump_stack+0x80/0xa0
[<ffff8000000bd324>] ___might_sleep+0x18c/0x1a0
[<ffff8000007a20ac>] __rt_spin_lock+0x2c/0x40
[<ffff8000007a2268>] rt_read_lock+0x40/0x58
[<ffff800000085328>] single_step_handler+0x38/0xd8
[<ffff800000082368>] do_debug_exception+0x58/0xb8
Exception stack(0xffff80834a1e7c80 to 0xffff80834a1e7da0)
7c80: ffffff9c ffffffff 92c23ba0 0000ffff 4a1e7e40 ffff8083 001bfcc4 ffff8000
7ca0: f2000400 00000000 00000000 00000000 4a1e7d80 ffff8083 0049501c ffff8000
7cc0: 00005402 00000000 00aaa210 ffff8000 4a1e7ea0 ffff8083 000833f4 ffff8000
7ce0: ffffff9c ffffffff 92c23ba0 0000ffff 4a1e7ea0 ffff8083 001bfcc0 ffff8000
7d00: 4a0fc400 ffff8083 00005402 00000000 4a1e7d40 ffff8083 00490324 ffff8000
7d20: ffffff9c 00000000 92c23ba0 0000ffff 000a0000 00000000 00000000 00000000
7d40: 00000008 00000000 00080000 00000000 92c23b8b 0000ffff 92c23b8e 0000ffff
7d60: 00000038 00000000 00001cb2 00000000 00000005 00000000 92d7b498 0000ffff
7d80: 01010101 01010101 92be9000 0000ffff 00000000 00000000 00000030 00000000
[<ffff8000000833f4>] el1_dbg+0x18/0x6c

This issue is similar with 62c6c61a("arm64: replace read_lock to rcu lock in
call_break_hook"), but comes to single_step_handler.

This also solves kgdbts boot test silent hang issue on 4.4 -rt kernel.

Signed-off-by: default avatarYang Shi <yang.shi@linaro.org>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent d7e9d594

arch/arm64/kernel/debug-monitors.c

+11 −10
Original line number Diff line number Diff line
@@ -186,20 +186,21 @@ static void clear_regs_spsr_ss(struct pt_regs *regs) 


/* EL1 Single Step Handler hooks */

static LIST_HEAD(step_hook);

static DEFINE_RWLOCK(step_hook_lock);

static DEFINE_SPINLOCK(step_hook_lock);



void register_step_hook(struct step_hook *hook)

{

	write_lock(&step_hook_lock);

	list_add(&hook->node, &step_hook);

	write_unlock(&step_hook_lock);

	spin_lock(&step_hook_lock);

	list_add_rcu(&hook->node, &step_hook);

	spin_unlock(&step_hook_lock);

}



void unregister_step_hook(struct step_hook *hook)

{

	write_lock(&step_hook_lock);

	list_del(&hook->node);

	write_unlock(&step_hook_lock);

	spin_lock(&step_hook_lock);

	list_del_rcu(&hook->node);

	spin_unlock(&step_hook_lock);

	synchronize_rcu();

}



/*
@@ -213,15 +214,15 @@ static int call_step_hook(struct pt_regs *regs, unsigned int esr) 
	struct step_hook *hook;

	int retval = DBG_HOOK_ERROR;



	read_lock(&step_hook_lock);

	rcu_read_lock();



	list_for_each_entry(hook, &step_hook, node)	{

	list_for_each_entry_rcu(hook, &step_hook, node)	{

		retval = hook->fn(regs, esr);

		if (retval == DBG_HOOK_HANDLED)

			break;

	}



	read_unlock(&step_hook_lock);

	rcu_read_unlock();



	return retval;

}