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Goncalves" To: Sebastian Andrzej Siewior Cc: Waiman Long , Catalin Marinas , Will Deacon , Mark Rutland , Clark Williams , Steven Rostedt , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Ada Couprie Diaz Subject: Re: [PATCH] arm64/entry: Don't disable preemption in debug_exception_enter() with RT kernel Message-ID: References: <20260519222524.886454-1-longman@redhat.com> <20260520061920.XCqBHe0x@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260520061920.XCqBHe0x@linutronix.de> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On Wed, May 20, 2026 at 08:19:20AM +0200, Sebastian Andrzej Siewior wrote: > On 2026-05-19 18:25:24 [-0400], Waiman Long wrote: > > Commit d8bb6718c4db ("arm64: Make debug exception handlers visible from > > RCU") introduces debug_exception_enter() and debug_exception_exit() > > where preemption is explicitly disabled. With a PREEMPT_RT debug kernel, > > the following bug report can happen. > … > > What kernel is this? I have backport (which is being tested) for v6.6 > and v6.12, the patches are from v6.17-rc1. Sebastian, hardware breakpoint and watchpoint handlers still call debug_exception_exit() and disable preemption on aarch64. That should happen on v7.1-rc4 indeed. The suggestion was to mimic what x86_64 does with notify_die() -> hw_breakpoint_exceptions_notify(). In ARM hw_breakpoint_exceptions_notify() is a stub that always returns NOTIFY_DONE. Luis > Sebastian > ---end quoted text---