Re: [PATCH 1/5] powerpc/kprobes: Remove preempt disable around call to get_kprobe() in arch_prepare_kprobe()
From: "Nicholas Piggin" <npiggin@gmail.com>
Date: 2022-11-07 10:15:41
On Fri Oct 21, 2022 at 3:28 AM AEST, Naveen N. Rao wrote:
arch_prepare_kprobe() is called from register_kprobe() via prepare_kprobe(), or through register_aggr_kprobe(), both with the kprobe_mutex held. Per the comment for get_kprobe(): /* * This routine is called either: * - under the 'kprobe_mutex' - during kprobe_[un]register(). * OR * - with preemption disabled - from architecture specific code. */
That comment should read [un]register_kprobe(), right?
As such, there is no need to disable preemption around the call to get_kprobe(). Drop the same.
And prepare_kprobe() and register_aggr_kprobe() are both called with kprobe_mutex held so you rely on the same protection. This seems to fix a lost-resched bug with preempt kernels too. Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
quoted hunk ↗ jump to hunk
Reported-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Naveen N. Rao <redacted> --- arch/powerpc/kernel/kprobes.c | 2 -- 1 file changed, 2 deletions(-)diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c index bd7b1a03545948..88f42de681e1f8 100644 --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c@@ -158,9 +158,7 @@ int arch_prepare_kprobe(struct kprobe *p) printk("Cannot register a kprobe on the second word of prefixed instruction\n"); ret = -EINVAL; } - preempt_disable(); prev = get_kprobe(p->addr - 1); - preempt_enable_no_resched(); /* * When prev is a ftrace-based kprobe, we don't have an insn, and it-- 2.38.0