From: Will Deacon <will@kernel•org>
To: "Rob Herring (Arm)" <robh@kernel•org>
Cc: Mark Rutland <mark.rutland@arm•com>,
Catalin Marinas <catalin.marinas@arm•com>,
Jonathan Corbet <corbet@lwn•net>,
Shuah Khan <skhan@linuxfoundation•org>,
Anshuman Khandual <anshuman.khandual@arm•com>,
linux-arm-kernel@lists•infradead.org,
linux-perf-users@vger•kernel.org, linux-kernel@vger•kernel.org,
linux-doc@vger•kernel.org
Subject: Re: [PATCH v4 3/6] arm64: hw_breakpoint: Add lockdep_assert_irqs_disabled() on install/uninstall
Date: Thu, 28 May 2026 11:57:31 +0100 [thread overview]
Message-ID: <ahgfmyZtPL5YPRCZ@willie-the-truck> (raw)
In-Reply-To: <20260407-arm-debug-8-9-v4-3-a4864e69b0ea@kernel.org>
On Tue, Apr 07, 2026 at 09:29:45AM -0500, Rob Herring (Arm) wrote:
> The breakpoint install/uninstall/restore code depends on interrupts
> being disabled. Make this requirement explicit with a
> lockdep_assert_irqs_disabled() assertion.
>
> Signed-off-by: Rob Herring (Arm) <robh@kernel•org>
> ---
> arch/arm64/kernel/hw_breakpoint.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
> index bb39bc759810..a9266dc710b4 100644
> --- a/arch/arm64/kernel/hw_breakpoint.c
> +++ b/arch/arm64/kernel/hw_breakpoint.c
> @@ -231,6 +231,8 @@ static int hw_breakpoint_control(struct perf_event *bp,
> enum dbg_active_el dbg_el = debug_exception_level(info->ctrl.privilege);
> u32 ctrl;
>
> + lockdep_assert_irqs_disabled();
This function (hw_breakpoint_control()) is static and only has three
callers:
1. Via the cpu hotplug CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING notifier
2. From arch_install_hw_breakpoint()
3. From arch_uninstall_hw_breakpoint()
So if we're called with irqs enabled, the core code has gone very wrong
and I don't think we should necessarily be checking that in the arch
backend. We also already have a WARN_ON(preemptible()) in
{enable,disable}_debug_monitors() so if you really want to add this then
please can you spell out why you're specifically concerned about the
preemption-disabled but irq-enabled case in the commit message?
Will
next prev parent reply other threads:[~2026-05-28 10:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-07 14:29 [PATCH v4 0/6] arm64: Add support for FEAT_Debugv8p9 Rob Herring (Arm)
2026-04-07 14:29 ` [PATCH v4 1/6] arm64: hw_breakpoint: Disallow breakpoints in no kprobe code Rob Herring (Arm)
2026-05-28 10:57 ` Will Deacon
2026-04-07 14:29 ` [PATCH v4 2/6] arm64: hw_breakpoint: Add additional kprobe excluded functions Rob Herring (Arm)
2026-04-07 14:29 ` [PATCH v4 3/6] arm64: hw_breakpoint: Add lockdep_assert_irqs_disabled() on install/uninstall Rob Herring (Arm)
2026-05-28 10:57 ` Will Deacon [this message]
2026-04-07 14:29 ` [PATCH v4 4/6] arm64/cpufeature: Add field details for ID_AA64DFR1_EL1 register Rob Herring (Arm)
2026-05-28 10:57 ` Will Deacon
2026-04-07 14:29 ` [PATCH v4 5/6] arm64/boot: Enable EL2 requirements for FEAT_Debugv8p9 Rob Herring (Arm)
2026-05-28 10:58 ` Will Deacon
2026-04-07 14:29 ` [PATCH v4 6/6] arm64: hw_breakpoint: Enable FEAT_Debugv8p9 Rob Herring (Arm)
2026-05-28 11:05 ` Will Deacon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ahgfmyZtPL5YPRCZ@willie-the-truck \
--to=will@kernel$(echo .)org \
--cc=anshuman.khandual@arm$(echo .)com \
--cc=catalin.marinas@arm$(echo .)com \
--cc=corbet@lwn$(echo .)net \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
--cc=linux-doc@vger$(echo .)kernel.org \
--cc=linux-kernel@vger$(echo .)kernel.org \
--cc=linux-perf-users@vger$(echo .)kernel.org \
--cc=mark.rutland@arm$(echo .)com \
--cc=robh@kernel$(echo .)org \
--cc=skhan@linuxfoundation$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox