From patchwork Wed Oct 23 13:17:20 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Jones X-Patchwork-Id: 13847063 Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) (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 DF7A3159583 for ; Wed, 23 Oct 2024 13:17:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.189 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729689451; cv=none; b=fz6//5AB00J8C1D3GemnyT2OwaG0DLJdZLXhRyHGmEOnItOTp8FGrbNaKrW21RkQCDdk+bQzM9fSLQwT46km2J5yA5m0IBW6DMGKRL13kzGm6xm6qFZcfjQZu25pXfW8QZsXb5NIOSt0rZk/nh0rxIJ3K39KDwOimA1fumxOoVg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729689451; c=relaxed/simple; bh=VxEExFJ5cT66ChsR+4TqWR6RdTnzv16Bxu3/mJ5sDTU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=S6m9BTikECVWc2//orQk3R9DvO6SwdjUBGTIshRllPRfhT4vCT2aVf/5a28FSbEDwtkJ0aU2QVNhl6o2FR01Us+ZGvKoH1so8UjnooHAGmPteVs3PsI6MImhuYhbTzidZfn72ioZ8yJkPPLBVOrTWYb0SVUiab42lFLrtuZ6h6k= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=R96KKr45; arc=none smtp.client-ip=91.218.175.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="R96KKr45" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1729689445; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QeV4UfkiS7XFzfn3GzKPrb95YL+mJ8EYcU6Ge+O/14M=; b=R96KKr45P98nWNOUWIJnWJDx/9nd3WZG25knN4pFUZzB4fuUvsjoVabJi4z3xcoy/ZHkVV CXySf4GOiO8G7USyOggyGxSnaR+X33cdujPH4+XrRKeS3u8v/fQaJMegQnZ05uEn/uHqqv b4cAIgKHO1E5RwIF5gyzjGNf6N80yJ0= From: Andrew Jones To: kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, kvmarm@lists.linux.dev Cc: atishp@rivosinc.com, jamestiotio@gmail.com, alexandru.elisei@arm.com, eric.auger@redhat.com Subject: [kvm-unit-tests PATCH 1/2] lib/on-cpus: Correct and simplify synchronization Date: Wed, 23 Oct 2024 15:17:20 +0200 Message-ID: <20241023131718.117452-5-andrew.jones@linux.dev> In-Reply-To: <20241023131718.117452-4-andrew.jones@linux.dev> References: <20241023131718.117452-4-andrew.jones@linux.dev> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT get/put_on_cpu_info() were trying to provide per-cpu locking for the per-cpu on_cpu info, but they were flawed since they would always set the "lock" since they were treating test_and_set/clear as cmpxchg (which they're not). Just revert to a normal spinlock to correct it. Also simplify the break case for on_cpu_async() - we don't care if func is NULL, we only care that the cpu is idle. And, finally, add a missing barrier to on_cpu_async(). Fixes: 018550041b38 ("arm/arm64: Remove spinlocks from on_cpu_async") Signed-off-by: Andrew Jones --- lib/on-cpus.c | 36 +++++++++++------------------------- 1 file changed, 11 insertions(+), 25 deletions(-) diff --git a/lib/on-cpus.c b/lib/on-cpus.c index 892149338419..f6072117fa1b 100644 --- a/lib/on-cpus.c +++ b/lib/on-cpus.c @@ -9,6 +9,7 @@ #include #include #include +#include bool cpu0_calls_idle; @@ -18,18 +19,7 @@ struct on_cpu_info { cpumask_t waiters; }; static struct on_cpu_info on_cpu_info[NR_CPUS]; -static cpumask_t on_cpu_info_lock; - -static bool get_on_cpu_info(int cpu) -{ - return !cpumask_test_and_set_cpu(cpu, &on_cpu_info_lock); -} - -static void put_on_cpu_info(int cpu) -{ - int ret = cpumask_test_and_clear_cpu(cpu, &on_cpu_info_lock); - assert(ret); -} +static struct spinlock lock; static void __deadlock_check(int cpu, const cpumask_t *waiters, bool *found) { @@ -81,18 +71,14 @@ void do_idle(void) if (cpu == 0) cpu0_calls_idle = true; - set_cpu_idle(cpu, true); - smp_send_event(); - for (;;) { + set_cpu_idle(cpu, true); + smp_send_event(); + while (cpu_idle(cpu)) smp_wait_for_event(); smp_rmb(); on_cpu_info[cpu].func(on_cpu_info[cpu].data); - on_cpu_info[cpu].func = NULL; - smp_wmb(); - set_cpu_idle(cpu, true); - smp_send_event(); } } @@ -110,17 +96,17 @@ void on_cpu_async(int cpu, void (*func)(void *data), void *data) for (;;) { cpu_wait(cpu); - if (get_on_cpu_info(cpu)) { - if ((volatile void *)on_cpu_info[cpu].func == NULL) - break; - put_on_cpu_info(cpu); - } + spin_lock(&lock); + if (cpu_idle(cpu)) + break; + spin_unlock(&lock); } on_cpu_info[cpu].func = func; on_cpu_info[cpu].data = data; + smp_wmb(); set_cpu_idle(cpu, false); - put_on_cpu_info(cpu); + spin_unlock(&lock); smp_send_event(); }