From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3C6F421858A; Thu, 24 Jul 2025 21:59:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753394394; cv=none; b=MgnIAgqhjASCvQJqhasahqZamxQ33f+RZrbkLWcya+AooST10bh7avIK4Jvz7bV4bUDKPsYid5iUQEvu2qhH9NjtU0OdxPl3xBxCnCdiLCtsk34EHgKN8SEZrxZVxrdS2/oHA6q6DBlmFrr/DzRVxof/8UiwAeno8XnvLiFd1lU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753394394; c=relaxed/simple; bh=enA0+R4KlVQsB2+gsMerGTr2ZGdR8MjJ8EpyD/BzHkc=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=O27DbTgeLk3IMSwIBH2MRDWUKuBd9nkOV+Zjb2M97P7I8/mlbewObtdpnWCAx8/659lIInHFjcsHak12inj5ahwc0scKs+uTLZGLoAAPc+9+NnVMnaekYzWNXXChqI/i34fR/kBaRyTfMrZ2i/7yZ5mGPqFcbjBJ9hUjRpWZr1Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=nejusQ7G; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=RPgv96XF; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="nejusQ7G"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="RPgv96XF" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1753394388; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=enA0+R4KlVQsB2+gsMerGTr2ZGdR8MjJ8EpyD/BzHkc=; b=nejusQ7GjW0lG9RPO1CF7sFmWk7heNnYtDgtu92R3MUQLyynbOxXgGMa+Y1XUhxaMGjKlL hfXtUmyWzfv8oeOZ44Oi0cW77l4vYRyquh9Vt+S+/RHA47HbEcymuh9fXE98xJod6iYJZN UJ+T5M78Uwxbyb3ombiEVuopskIUG4JjrA+JtLYfxb4HNB7kVNF63eZ7vFy0qEJYveLQ30 3F0ttK9MfuorP9ZCJaZxs6WmhUXyElWth0FXxYOqiGKrdXSQT+MtkkzBMgejDBlIC57DY2 38Q+aeFb1690mmD530z7Qjy+4vsQZqsMxHPikAkMdyFZ0R0bLOvbGs1YdGxDig== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1753394388; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=enA0+R4KlVQsB2+gsMerGTr2ZGdR8MjJ8EpyD/BzHkc=; b=RPgv96XFx0+GjNQ+OWv50r4D2NDkzYXvPbVdEHBVaYwVlbHaxBD7Mej4cX5eY9PL+8krww 5yGhPvRojlJTzvCw== To: Lyude Paul , Peter Zijlstra Cc: Boqun Feng , Dirk Behme , rust-for-linux@vger.kernel.org, Danilo Krummrich , airlied@redhat.com, Ingo Molnar , will@kernel.org, Waiman Long , linux-kernel@vger.kernel.org, Miguel Ojeda , Alex Gaynor , wedsonaf@gmail.com, Gary Guo , =?utf-8?Q?Bj=C3=B6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , aliceryhl@google.com, Trevor Gross Subject: Re: w/r/t "irq & spin_lock: Add counted interrupt disabling/enabling": holes in pcpu_hot? In-Reply-To: <012ccaab7df3d884f924d6af52dd36ebc4da80ce.camel@redhat.com> References: <20241018055125.2784186-2-boqun.feng@gmail.com> <87a5eu7gvw.ffs@tglx> <20241023195152.GE11151@noisy.programming.kicks-ass.net> <012ccaab7df3d884f924d6af52dd36ebc4da80ce.camel@redhat.com> Date: Thu, 24 Jul 2025 23:59:46 +0200 Message-ID: <874iv1qmgd.ffs@tglx> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Thu, Jul 24 2025 at 16:36, Lyude Paul wrote: > Hey! Sorry to be a bit late here but I just noticed this comment in your email > that I didn't before > > On Wed, 2024-10-23 at 21:51 +0200, Peter Zijlstra wrote: >> We still have a few holes in pcpu_hot iirc. > > I assume you mean we still have space for adding things into pcpu_hot? And if > so, where exactly are these holes? At some point when working on this series I > attempted adding a single unsigned long to pcpu_hot and the build failed as a > result of not having enough space. But if there's somewhere we can add > something else, that might actually help with a few of the issues in this > patch series That's the current lot we have. ffffffff82f6a000 D __per_cpu_hot_start ffffffff82f6a000 D hardirq_stack_ptr ffffffff82f6a008 D __ref_stack_chk_guard ffffffff82f6a008 D __stack_chk_guard ffffffff82f6a010 D const_cpu_current_top_of_stack ffffffff82f6a010 D cpu_current_top_of_stack ffffffff82f6a018 D const_current_task ffffffff82f6a018 D current_task ffffffff82f6a020 D __x86_call_depth ffffffff82f6a028 D this_cpu_off ffffffff82f6a030 D __preempt_count ffffffff82f6a034 D cpu_number ffffffff82f6a038 D __softirq_pending ffffffff82f6a03a D hardirq_stack_inuse ffffffff82f6a03b D __per_cpu_hot_end So there is a 5 byte hole there at the end, which is obviously too small for an unsigned long on 64-bit :)