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arm64: Remove unneeded rcu_read_lock from debug handlers 

Remove rcu_read_lock()/rcu_read_unlock() from debug exception
handlers since we are sure those are not preemptible and
interrupts are off.

Acked-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Masami Hiramatsu 2019-07-25 17:16:25 +09:00 committed by Will Deacon
parent ee07b93e77
commit 760d8ed069
1 changed files with 8 additions and 6 deletions
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14
arch/arm64/kernel/debug-monitors.c
View File

@ -207,16 +207,16 @@ static int call_step_hook(struct pt_regs *regs, unsigned int esr)
list = user_mode(regs) ? &user_step_hook : &kernel_step_hook;
rcu_read_lock();
/*
* Since single-step exception disables interrupt, this function is
* entirely not preemptible, and we can use rcu list safely here.
*/
list_for_each_entry_rcu(hook, list, node) {
retval = hook->fn(regs, esr);
if (retval == DBG_HOOK_HANDLED)
break;
}
rcu_read_unlock();
return retval;
}
NOKPROBE_SYMBOL(call_step_hook);
@ -305,14 +305,16 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr)
list = user_mode(regs) ? &user_break_hook : &kernel_break_hook;
rcu_read_lock();
/*
* Since brk exception disables interrupt, this function is
* entirely not preemptible, and we can use rcu list safely here.
*/
list_for_each_entry_rcu(hook, list, node) {
unsigned int comment = esr & ESR_ELx_BRK64_ISS_COMMENT_MASK;
if ((comment & ~hook->mask) == hook->imm)
fn = hook->fn;
}
rcu_read_unlock();
return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
}