From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <45D4661D.7010506@domain.hid> Date: Thu, 15 Feb 2007 14:54:37 +0100 From: Wolfgang Grandegger MIME-Version: 1.0 References: <45D35545.20100@domain.hid> <45D45F63.5050009@domain.hid> <45D461DC.20303@domain.hid> In-Reply-To: <45D461DC.20303@domain.hid> Content-Type: multipart/mixed; boundary="------------060402090903090400000604" Subject: [Xenomai-core] Re: RT-CAN tx_sem List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: xenomai-core This is a multi-part message in MIME format. --------------060402090903090400000604 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Jan Kiszka wrote: > Wolfgang Grandegger wrote: >> Hi Jan, >> >> Jan Kiszka wrote: >>> Hi Wolfgang, >>> >>> fiddling with the CAN utils, I noticed the behaviour that rtcansend on >>> freshly registered but stopped devices simply blocks. And when you >>> meanwhile call rtcanconfig up on that device, rtcansend will continue to >>> block. >> I see the expected behavior on stopped devices: >> >> bash-2.05b# rtcansend rtcan0 >> rt_dev_send: Network is down >> >> This is, because the tx_sem is marked "destroyed" already when the >> device gets initialized. I wonder why your app blocks. > > Unlikely, because the sem is _not_ marked destroyed on startup: > > http://www.rts.uni-hannover.de/xenomai/lxr/source/ksrc/drivers/can/rtcan_dev.c#181 You missed /* Set dummy state for following call */ dev->state = CAN_STATE_ACTIVE; /* Enter reset mode */ rtcan_sja_mode_stop(dev, NULL); in the init part of rtcan_sja1000.c and rtcan_mscan.c, ... > > In case it makes a subtle difference: I tested with xeno_can_virt, but I > think I saw the same effect on real SJA1000 hw as well. ... which is missing in rtcan_virt.c. I already thought moving it to the common part. The attached patch fixes that. >>> The reason is that during startup of CAN devices the tx-semaphore is >>> re-initialised while it is already set up during device registration. >>> Re-init on an already initialised rtdm_sem is, say, undefined. >> That makes definitely trouble. A CAN_MODE_START should only start the >> device if it's not active. The attached patch fixes this. Another >> possibility would be to force a CAN_MODE_STOP in case the device is >> already active (=restart). >> >>> So rtdm_sem should better only be initialised/destroyed by the drivers. >>> Trying to send on a shut down CAN device could be catched differently, >>> e.g. via the device state. This likely needs more thoughts, take it as a >>> note that $something should be done. >> With the fix above I do not see further problems with the existing >> implementation using the "destroyed" state to mark the device unavailable. > > The problem of double init remains. I don't think that the sem state > should be used for encoding the CAN device state towards potential senders. As I see it, Sebastian's trick saves code and synchronization. Wolfgang. --------------060402090903090400000604 Content-Type: text/x-patch; name="xenomai-rtcan-txsem2.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="xenomai-rtcan-txsem2.patch" + diff -u xenomai/ksrc/drivers/can/rtcan_dev.c.TXSEM xenomai/ksrc/drivers/can/rtcan_dev.c --- xenomai/ksrc/drivers/can/rtcan_dev.c.TXSEM 2007-02-15 11:21:43.000000000 +0100 +++ xenomai/ksrc/drivers/can/rtcan_dev.c 2007-02-15 14:52:20.000000000 +0100 @@ -176,9 +176,9 @@ rtdm_lock_init(&dev->device_lock); - /* Init TX Semaphore, will be destroyed forthwith - * when setting stop mode */ + /* Init and destroy TX semaphore to mark TX unavailable. */ rtdm_sem_init(&dev->tx_sem, 0); + rtdm_sem_destroy(&dev->tx_sem); #ifdef RTCAN_USE_REFCOUNT atomic_set(&dev->refcount, 0); #endif + diff -u xenomai/ksrc/drivers/can/rtcan_raw_dev.c.TXSEM xenomai/ksrc/drivers/can/rtcan_raw_dev.c --- xenomai/ksrc/drivers/can/rtcan_raw_dev.c.TXSEM 2007-02-15 11:21:43.000000000 +0100 +++ xenomai/ksrc/drivers/can/rtcan_raw_dev.c 2007-02-15 14:16:16.000000000 +0100 @@ -193,7 +193,8 @@ switch (request) { case SIOCSCANMODE: mode = (can_mode_t *)&ifr->ifr_ifru; - if (dev->do_set_mode) + if (dev->do_set_mode && + !(*mode == CAN_MODE_START && CAN_STATE_OPERATING(dev->state))) ret = dev->do_set_mode(dev, *mode, &lock_ctx); break; --------------060402090903090400000604--