linux-kernel - Re: [PATCH v2 0/6] unwind, arm64: add sframe unwinder for kernel

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Message-ID: <20251117184223.3c03fe92@gandalf.local.home>
Date: Mon, 17 Nov 2025 18:42:23 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Dylan Hatch <dylanbhatch@...gle.com>, Puranjay Mohan
 <puranjay12@...il.com>, Song Liu <song@...nel.org>, Indu Bhagat
 <indu.bhagat@...cle.com>, Peter Zijlstra <peterz@...radead.org>, Will
 Deacon <will@...nel.org>, Catalin Marinas <catalin.marinas@....com>, Jiri
 Kosina <jikos@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>,
 Weinan Liu <wnliu@...gle.com>, Mark Rutland <mark.rutland@....com>, Ian
 Rogers <irogers@...gle.com>, linux-toolchains@...r.kernel.org,
 linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
 joe.lawrence@...hat.com, Puranjay Mohan <puranjay@...nel.org>
Subject: Re: [PATCH v2 0/6] unwind, arm64: add sframe unwinder for kernel

On Mon, 17 Nov 2025 15:06:32 -0800
Josh Poimboeuf <jpoimboe@...nel.org> wrote:

> The ORC unwinder marks the unwind "unreliable" if it has to fall back to
> frame pointers.
> 
> But that's not a problem for livepatch because it only[*] unwinds
> blocked/sleeping tasks, which shouldn't have BPF on their stack anyway.
> 
> [*] with one exception: the task calling into livepatch

It may be a problem with preempted tasks right? I believe with PREEMPT_LAZY
(and definitely with PREEMPT_RT) BPF programs can be preempted.

-- Steve