From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Subject: Re: [PATCH, RFC 21/30] isdn: divert, hysdn: fix interruptible_sleep_on race Date: Thu, 02 Jan 2014 19:01:15 +0400 Message-ID: <52C57F3B.9070509@cogentembedded.com> References: <1388664474-1710039-1-git-send-email-arnd@arndb.de> <1388664474-1710039-22-git-send-email-arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Karsten Keil , netdev@vger.kernel.org To: Arnd Bergmann , linux-kernel@vger.kernel.org Return-path: In-Reply-To: <1388664474-1710039-22-git-send-email-arnd@arndb.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hello. On 02-01-2014 16:07, Arnd Bergmann wrote: > These two drivers use identical code for their procfs status > file handling, which contains a small race against status > data becoming available while reading the file. > This uses wait_event_interruptible instead to fix this > particular race and eventually get rid of all sleep_on > instances. There seems to be another race involving > multiple concurrent readers of the same procfs file, which > I don't try to fix here. > Signed-off-by: Arnd Bergmann > Cc: Karsten Keil > Cc: netdev@vger.kernel.org > --- > drivers/isdn/divert/divert_procfs.c | 7 ++++--- > drivers/isdn/hysdn/hysdn_proclog.c | 7 ++++--- > 2 files changed, 8 insertions(+), 6 deletions(-) > diff --git a/drivers/isdn/divert/divert_procfs.c b/drivers/isdn/divert/divert_procfs.c > index fb4f1ba..1c5dc34 100644 > --- a/drivers/isdn/divert/divert_procfs.c > +++ b/drivers/isdn/divert/divert_procfs.c > @@ -86,12 +86,13 @@ isdn_divert_read(struct file *file, char __user *buf, size_t count, loff_t *off) > struct divert_info *inf; > int len; > > - if (!*((struct divert_info **) file->private_data)) { > + if (!(inf = *((struct divert_info **) file->private_data))) { checkpatch.pl shouldn't approve assignment inside *if*. Though you're moving it from the existing code, it wouldn't hurt to fix it. > if (file->f_flags & O_NONBLOCK) > return -EAGAIN; > - interruptible_sleep_on(&(rd_queue)); > + wait_event_interruptible(rd_queue, (inf = > + *((struct divert_info **) file->private_data))); Parens around assignment are hardly useful. > } > - if (!(inf = *((struct divert_info **) file->private_data))) > + if (!inf) > return (0); > > inf->usage_cnt--; /* new usage count */ > diff --git a/drivers/isdn/hysdn/hysdn_proclog.c b/drivers/isdn/hysdn/hysdn_proclog.c > index b61e8d5..7b5fd8f 100644 > --- a/drivers/isdn/hysdn/hysdn_proclog.c > +++ b/drivers/isdn/hysdn/hysdn_proclog.c > @@ -175,14 +175,15 @@ hysdn_log_read(struct file *file, char __user *buf, size_t count, loff_t *off) > int len; > hysdn_card *card = PDE_DATA(file_inode(file)); > > - if (!*((struct log_data **) file->private_data)) { > + if (!(inf = *((struct log_data **) file->private_data))) { Here too checkpatch.pk should complain... > struct procdata *pd = card->proclog; > if (file->f_flags & O_NONBLOCK) > return (-EAGAIN); > > - interruptible_sleep_on(&(pd->rd_queue)); > + wait_event_interruptible(pd->rd_queue, (inf = > + *((struct log_data **) file->private_data))); And parens hardly needed. WBR, Sergei