From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from wa-out-1112.google.com ([209.85.146.178]) by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux)) id 1Jj95E-0001ME-J2 for linux-mtd@lists.infradead.org; Tue, 08 Apr 2008 08:21:41 +0000 Received: by wa-out-1112.google.com with SMTP id v33so1461901wah.2 for ; Tue, 08 Apr 2008 01:21:34 -0700 (PDT) Message-ID: Date: Tue, 8 Apr 2008 10:21:34 +0200 From: "Dmitry Adamushko" To: "Andrew Morton" Subject: Re: [PATCH] mtd/chips: add missing set_current_state() to cfi_{amdstd, staa}_sync() In-Reply-To: <20080407161555.3dd540f9.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <1207251503.6300.9.camel@earth> <20080407161555.3dd540f9.akpm@linux-foundation.org> Cc: dwmw2@infradead.org, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 08/04/2008, Andrew Morton wrote: > On Thu, 03 Apr 2008 21:38:23 +0200 > Dmitry Adamushko wrote: > > > From: Dmitry Adamushko > > Subject: [mtd/chips] add missing set_current_state() to cfi_{amdstd,staa}_sync() > > > > cfi_amdstd_sync() and cfi_staa_sync() call schedule() without changing > > task's state appropriately. > > > > In case of e.g. chip->state == FL_ERASING, cfi_*_sync() will be busy-looping > > either redundantly for a fixed interval of time (for SCHED_NORMAL tasks) or > > possibly endlessly (for RT tasks and UP). > > > > Signed-off-by: Dmitry Adamushko > > > > --- > > > > diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c > > index d072e87..458d477 100644 > > --- a/drivers/mtd/chips/cfi_cmdset_0002.c > > +++ b/drivers/mtd/chips/cfi_cmdset_0002.c > > @@ -1763,6 +1763,7 @@ static void cfi_amdstd_sync (struct mtd_info *mtd) > > > > default: > > /* Not an idle state */ > > + set_current_state(TASK_UNINTERRUPTIBLE); > > add_wait_queue(&chip->wq, &wait); > > > > spin_unlock(chip->mutex); > > diff --git a/drivers/mtd/chips/cfi_cmdset_0020.c b/drivers/mtd/chips/cfi_cmdset_0020.c > > index b344ff8..492e2ab 100644 > > --- a/drivers/mtd/chips/cfi_cmdset_0020.c > > +++ b/drivers/mtd/chips/cfi_cmdset_0020.c > > @@ -1015,6 +1015,7 @@ static void cfi_staa_sync (struct mtd_info *mtd) > > > > default: > > /* Not an idle state */ > > + set_current_state(TASK_UNINTERRUPTIBLE); > > add_wait_queue(&chip->wq, &wait); > > > > spin_unlock_bh(chip->mutex); > > > The change certainly looks correct. Has it been runtime tested? It has been tested with an oldish 2.6.8.1 where the problem initially occured. It was a RT task that happened to close an mtd fd (and resulting in ->sync() being called) and ran in the middle of the ->erase op... resulting in a "nice" endless loop. The versions of cfi_{amdstd,staa}_sync() in the mainline look not that much different from the respective versions in 2.6.8.1. I guess, it went unnoticed for so long time due to : (1) apps. don't often directly open/close() fd for mtd partitions; (2) a race against ->erase() (or smth else) is rare; (3) if (1) is not true, then an app. is still unlikely to be RT (in which case, a task just loops until its timeslice is gone). > > Thanks. > -- Best regards, Dmitry Adamushko