From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 17 Oct 2002 04:22:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 17 Oct 2002 04:22:40 -0400 Received: from [199.203.76.13] ([199.203.76.13]:9624 "EHLO linux.optibase.co.il") by vger.kernel.org with ESMTP id ; Thu, 17 Oct 2002 04:22:35 -0400 Message-ID: <3DAE749B.3040305@optibase.com> Date: Thu, 17 Oct 2002 10:28:11 +0200 From: Constantine Gavrilov Organization: Optibase User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.9) Gecko/20020313 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Linux Kernel Subject: Problem implementing poll method Content-Type: multipart/mixed; boundary="------------010900030209060508050805" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------010900030209060508050805 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit -- ---------------------------------------- Constantine Gavrilov Linux Leader Optibase Ltd 7 Shenkar St, Herzliya 46120, Israel Phone: (972-9)-970-9140 Fax: (972-9)-958-6099 ---------------------------------------- --------------010900030209060508050805 Content-Type: text/plain; name="let.txt" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="let.txt" Hi, I have a problem implementing poll method. I have written a driver for MPEG encoder card. The user-space SDK needs to be able to wait for a certain event that is reported by the interrupt handler. I have done it using ioctl method, like this: u32 timeout=milliseconds * HZ / 1000; set_bit(0, &dev->fintwait); if(test_bit(0, &dev->fintwait)) { interruptible_sleep_on_timeout(&dev->interrupt_queue,timeout); if (signal_pending(current)) { printk(KERN_ERR "optenc: IntWait restarted by signal\n"); return -ERESTARTSYS; } if(test_bit(0, &dev->fintwait)) { printk(KERN_ERR "optenc: intwait timeout\n"); ..//returns wait timeout } else { ...//returns wait OK } } //returns wait OK The interrupt handler wakes up the queue and updates dev->fintwait like this: clear_bit(0, &dev->fintwait); wake_up_interruptible(&dev->interrupt_queue); It worked very well for me. I wanted to implement the same wait using the poll method. So, my poll function looks like this: unsigned int optenc_poll(struct file *filp, poll_table *wait_table) { unsigned int mask = 0; struct mydev *dev = filp->private_data; set_bit(0, &dev->fintwait); if(test_bit(0, &dev->fintwait)) { poll_wait(filp, &dev->interrupt_queue, wait_table); if(test_bit(0, &dev->fintwait)) return mask; else { mask |= POLLIN |POLLRDNORM; return mask; } } else { mask |= POLLIN |POLLRDNORM; return mask; } } Seems straightforward and the same thing as above. But, I have the following problems: a) I have a lot of calls with wait_table = NULL and poll_wait does not block. I always do select on one file descriptor only and I never use zero timeout, so I do not understand the reason for it. b) Even when wait_table is not NULL, poll_wait returns before (!!) interrupt handler wakes up the queue. I have checked it with printk. It always like this: set_bit poll_wait poll_wait returns and test_bit is true wake_up and clear_bit It is like poll_wait does not seem to block and I have spurious calles with wait_table == NULL. Any ideas? Just to verify, the user-space wait function looks like this : BOOL Wait(int timeout) { fd_set set; struct timeval tv; int retval; FD_ZERO(&set); FD_SET(fd, &set); tv.tv_sec = timeout/1000; tv.tv_usec = (timeout%1000)*1000; int rc=select(fd+1, &set, NULL, NULL, &tv); if(rc == -1) { PERROR("select"); return FALSE; } if(rc == 1) return TRUE; else return FALSE; } I use 2.4.18-pre7ac1 and I have also checked stock RedHat's 2.4.9-34. --------------010900030209060508050805--