Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932277AbbHXPhW (ORCPT ); Mon, 24 Aug 2015 11:37:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51371 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750941AbbHXPg7 (ORCPT ); Mon, 24 Aug 2015 11:36:59 -0400 Date: Mon, 24 Aug 2015 17:34:31 +0200 From: Oleg Nesterov To: "Paul E. McKenney" Cc: Ingo Molnar , Linus Torvalds , Peter Zijlstra , Tejun Heo , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/8] Add rcu_sync infrastructure to avoid _expedited() in percpu-rwsem Message-ID: <20150824153431.GB24949@redhat.com> References: <20150821174230.GA17867@redhat.com> <20150822163810.GV11078@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150822163810.GV11078@linux.vnet.ibm.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3876 Lines: 139 On 08/22, Paul E. McKenney wrote: > > Queued for testing, thank you, Oleg! Thanks Paul! > Right now, this is mostly relying on 0day and -next testing. Any thoughts > for a useful torture test for this? Right now I do not have any idea how to write the meaningful test for rcu_sync... Perhaps something like struct rcu_sync_struct rss; spinlock_t lock; int A, B; void read(void) { rcu_read_lock(); bool need_lock = !rcu_sync_is_idle(&rss); if (need_lock) spin_lock(&lock); BUG_ON(A != B); if (need_lock) spin_unlock(&lock); rcu_read_unlock(); } void modify(void) { rcu_sync_enter(&rss); spin_lock(&lock); A++; B++; spin_unlock(&lock); rcu_sync_exit(&rss); } makes sense... I'll try to think. > One approach would be to treat it > like a reader-writer lock. Other thoughts? I booted the kernel with the additional patch below, and nothing bad has happened, it continues to print Writes: Total: 2 Max/Min: 0/0 Fail: 0 Reads : Total: 2 Max/Min: 0/0 Fail: 0 However, I do not know what this code actually does, so currently I have no idea if this test makes any sense for percpu_rw_semaphore. Oleg. --- diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c index ec8cce2..62561ec 100644 --- a/kernel/locking/locktorture.c +++ b/kernel/locking/locktorture.c @@ -55,7 +55,7 @@ torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable"); torture_param(bool, verbose, true, "Enable verbose debugging printk()s"); -static char *torture_type = "spin_lock"; +static char *torture_type = "rwsem_lock"; module_param(torture_type, charp, 0444); MODULE_PARM_DESC(torture_type, "Type of lock to torture (spin_lock, spin_lock_irq, mutex_lock, ...)"); @@ -361,10 +361,12 @@ static struct lock_torture_ops mutex_lock_ops = { .name = "mutex_lock" }; -static DECLARE_RWSEM(torture_rwsem); -static int torture_rwsem_down_write(void) __acquires(torture_rwsem) +#include +static struct percpu_rw_semaphore pcpu_rwsem; + +static int torture_rwsem_down_write(void) __acquires(pcpu_rwsem) { - down_write(&torture_rwsem); + percpu_down_write(&pcpu_rwsem); return 0; } @@ -384,14 +386,14 @@ static void torture_rwsem_write_delay(struct torture_random_state *trsp) #endif } -static void torture_rwsem_up_write(void) __releases(torture_rwsem) +static void torture_rwsem_up_write(void) __releases(pcpu_rwsem) { - up_write(&torture_rwsem); + percpu_up_write(&pcpu_rwsem); } -static int torture_rwsem_down_read(void) __acquires(torture_rwsem) +static int torture_rwsem_down_read(void) __acquires(pcpu_rwsem) { - down_read(&torture_rwsem); + percpu_down_read(&pcpu_rwsem); return 0; } @@ -411,9 +413,9 @@ static void torture_rwsem_read_delay(struct torture_random_state *trsp) #endif } -static void torture_rwsem_up_read(void) __releases(torture_rwsem) +static void torture_rwsem_up_read(void) __releases(pcpu_rwsem) { - up_read(&torture_rwsem); + percpu_up_read(&pcpu_rwsem); } static struct lock_torture_ops rwsem_lock_ops = { @@ -645,6 +647,11 @@ static int __init lock_torture_init(void) &rwsem_lock_ops, }; + /* + * TODO: DECLARE_PERCPU_RWSEM(). The patch already exists. + */ + BUG_ON(percpu_init_rwsem(&pcpu_rwsem)); + if (!torture_init_begin(torture_type, verbose, &torture_runnable)) return -EBUSY; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/