From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ganesh Mahendran Subject: Re: [PATCH v2] PM / wakeup: use seq_open() to show wakeup stats Date: Wed, 14 Mar 2018 09:33:33 +0800 Message-ID: References: <1520239666-2964-1-git-send-email-opensource.ganesh@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Andy Shevchenko Cc: "Rafael J. Wysocki" , Pavel Machek , "Brown, Len" , "Rafael J. Wysocki" , Greg Kroah-Hartman , Linux PM , Linux Kernel Mailing List List-Id: linux-pm@vger.kernel.org Hi, Andy 2018-03-14 0:39 GMT+08:00 Andy Shevchenko : > On Mon, Mar 5, 2018 at 10:47 AM, Ganesh Mahendran > wrote: >> single_open() interface requires that the whole output must >> fit into a single buffer. This will lead to timeout when >> system memory is not in a good situation. >> >> This patch use seq_open() to show wakeup stats. This method >> need only one page, so timeout will not be observed. > >> + if (n == 0) { >> + seq_puts(m, "name\t\tactive_count\tevent_count\twakeup_count\t" >> + "expire_count\tactive_since\ttotal_time\tmax_time\t" >> + "last_change\tprevent_suspend_time\n"); >> + } > > Can't you do this once at ->open() stage, for example? We can not put this at ->open(). Because in seq_open(), the buffer is not ready, the seq buffer is allocated in seq_read(). Thanks. > >> static int wakeup_sources_stats_open(struct inode *inode, struct file *file) >> { >> - return single_open(file, wakeup_sources_stats_show, NULL); >> + return seq_open_private(file, &wakeup_sources_stats_seq_ops, sizeof(int)); >> } > > -- > With Best Regards, > Andy Shevchenko