| Message ID | 156378175027.12011.5591853683946780785.stgit@devnote2 (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: kprobes: Fix some bugs in arm64 kprobes | expand |
On Mon, Jul 22, 2019 at 04:49:11PM +0900, Masami Hiramatsu wrote: > Remove rcu_read_lock()/rcu_read_unlock() from debug exception > handlers since we are sure those are not preemptible and > interrupts are off. > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > Cc: Paul E. McKenney <paulmck@linux.ibm.com> From an RCU viewpoint: Acked-by: Paul E. McKenney <paulmck@linux.ibm.com> > --- > arch/arm64/kernel/debug-monitors.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c > index f8719bd30850..48222a4760c2 100644 > --- a/arch/arm64/kernel/debug-monitors.c > +++ b/arch/arm64/kernel/debug-monitors.c > @@ -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; > } >
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index f8719bd30850..48222a4760c2 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -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; }
Remove rcu_read_lock()/rcu_read_unlock() from debug exception handlers since we are sure those are not preemptible and interrupts are off. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Cc: Paul E. McKenney <paulmck@linux.ibm.com> --- arch/arm64/kernel/debug-monitors.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)