From nobody Thu Nov 28 12:53:36 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1C4F91D079B; Wed, 2 Oct 2024 14:57:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727881068; cv=none; b=ZpZVFccqSDJ3h5nmo3l/4F0ZFLZ0LAl6MfSYTHYRF+AF5Xau/YASRUDYb7bbZiNUUhKdrRxXZysvvmhq4nmwNIjQFV/zrZ/BhN8miNfb6wJeH3ff+D+t6m4nKS3Qzi7D5kSwWy7ErbQpl0oasJ2ZQHQQEH+I8o4Nj3Qn7mZI+h8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727881068; c=relaxed/simple; bh=52YRPDjGp4dDviquEXrrl2kjbqpQryVts8kljcTPeDY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hzRGxVNPjSSXvmenqZOIBt9vW2WSZ1h0KtxzlBKpNOkXASY53nnFaRP8SrGzvZznA+HcCVJELxKnbUG2spzXmnEvIiQe3c+b7tWqRb1h8XqUr3vyNNRurugvD750sjfu5Z+o2cyg36SpNrYxl7rWPE1GY05zrQrA+wQV1hGta9w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F75B7Wsv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="F75B7Wsv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B3FB1C4CEC2; Wed, 2 Oct 2024 14:57:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727881067; bh=52YRPDjGp4dDviquEXrrl2kjbqpQryVts8kljcTPeDY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=F75B7WsvBbvuxc7fsu+By/22DRQxkIj+tWtpyw0rstH6Zr3zHNGV9P2WpR1tPS9Pg wX0aTUxv2tqrMA6ODjShbWOCL9IK0IzmlpiBOZpiQrOO1tnQc7e5P4apJk5HaFxhXn TAuv7M37lNIni9xqcaFW5ZZ1YsrygDYRNI69oZe3MyqVp+beYogl0UGsSjfG0PN5pg x+IPQwsW+cqGnQMQvKjX5A+O/xpcdfYDxZBM10K39BqaC4Ia2j1YqRfBsIEKdfagNT 7JGDSbaZSIBCX+sGXxS5E3NAf9cbQ2/nl+Pd9cVSRSMofSthj9Ig/9fF7D+NfB5LbL RwRcag8PXKBjQ== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Boqun Feng , Joel Fernandes , Neeraj Upadhyay , "Paul E . McKenney" , Uladzislau Rezki , Zqiang , rcu Subject: [PATCH 1/3] rcu/nocb: Use switch/case on NOCB timer state machine Date: Wed, 2 Oct 2024 16:57:36 +0200 Message-ID: <20241002145738.38226-2-frederic@kernel.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20241002145738.38226-1-frederic@kernel.org> References: <20241002145738.38226-1-frederic@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" It's more convenient to benefit from the fallthrough feature of switch / case to handle the timer state machine. Also a new state is about to be added that will take advantage of it. No intended functional change. Signed-off-by: Frederic Weisbecker --- kernel/rcu/tree_nocb.h | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 97b99cd06923..2fb803f863da 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -271,22 +271,35 @@ static void wake_nocb_gp_defer(struct rcu_data *rdp, = int waketype, =20 raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags); =20 - /* - * Bypass wakeup overrides previous deferments. In case of - * callback storms, no need to wake up too early. - */ - if (waketype =3D=3D RCU_NOCB_WAKE_LAZY && - rdp->nocb_defer_wakeup =3D=3D RCU_NOCB_WAKE_NOT) { - mod_timer(&rdp_gp->nocb_timer, jiffies + rcu_get_jiffies_lazy_flush()); - WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype); - } else if (waketype =3D=3D RCU_NOCB_WAKE_BYPASS) { + switch (waketype) { + case RCU_NOCB_WAKE_BYPASS: + /* + * Bypass wakeup overrides previous deferments. In case of + * callback storms, no need to wake up too early. + */ mod_timer(&rdp_gp->nocb_timer, jiffies + 2); WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype); - } else { + break; + case RCU_NOCB_WAKE_LAZY: + if (rdp->nocb_defer_wakeup =3D=3D RCU_NOCB_WAKE_NOT) { + mod_timer(&rdp_gp->nocb_timer, jiffies + rcu_get_jiffies_lazy_flush()); + WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype); + } + /* + * If the timer is already armed, a non-lazy enqueue may have happened + * in-between. Don't delay it and fall-through. + */ + break; + case RCU_NOCB_WAKE: + fallthrough; + case RCU_NOCB_WAKE_FORCE: if (rdp_gp->nocb_defer_wakeup < RCU_NOCB_WAKE) mod_timer(&rdp_gp->nocb_timer, jiffies + 1); if (rdp_gp->nocb_defer_wakeup < waketype) WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype); + break; + default: + WARN_ON_ONCE(1); } =20 raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags); --=20 2.46.0