Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
Hi Lukasz, On Wed, 12 Nov 2014 11:11:33 -0700 Stephen Warren swar...@wwwdotorg.org wrote: On 11/12/2014 09:45 AM, Wolfgang Denk wrote: Dear Lukasz, In message 20141112152949.1fe6ce3c@amdc2363 you wrote: But this is a bug. Papering over is not a good idea. It should be analyzed, reported, and finally fixed. I've debugged the script with strace. Thanks a lot for that! The problem is with umount() syscall: ... I need to debug the syscall in the kernel. I have a gut feeling that this might be a problem somewhere with the USB stuff that is involved here. Maybe enabling some degug messages for the USB subsystem gives some more information? If this really is related to USB only, it may be worth asking on the linux-usb mailing list to see if anyone already unerstands the issue. Frankly speaking, I'm personally curious why such things happen. I may look into the issue in my spare :-) time. In spite of this, I agree with Stephen: Irrespective of all this though, even if there is a kernel issue and it can be fixed, I still think we should apply this patch, because the issue currently affects people. At the very least it will until some kernel fix is rolled out to everyone's distro, which will be a while no matter what. +1 The problem seems to be with long time running linux. The error seems to be orthogonal to our u-boot's UMS work. ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot Best regards, Lukasz Majewski Applied to u-boot-dfu tree. Thanks. -- Best regards, Lukasz Majewski Samsung RD Institute Poland (SRPOL) | Linux Platform Group ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
Hi Wolfgang, Dear Stephen, In message 545d40e1.2030...@wwwdotorg.org you wrote: My gut feeling is that there might be some USB driver error involved here. Where I've seen this is writing to an SD card in a USB-based SD card reader. I have a fairly regular amd64 machine running Ubuntu. I put the loop above into my own scripts that mount an SD card, copy new data to it, and then immediately unmount it for the same reason that Lukasz made this patch; umount doesn't always unmount. I did this so long ago that I don't recall which Ubuntu version I had at the time, nor the kernel version. It was *probably* Ubuntu 10.04 or 12.10 though. Now I'm on 14.04, but have no idea if I still need the loop since it's already in place:-) But this is a bug. Papering over is not a good idea. It should be analyzed, reported, and finally fixed. I've debugged the script with strace. The problem is with umount() syscall: [pid 23296] umount(/mnt/tmp-ums-test, 0) = -1 EBUSY (Device or resource busy) It is somehow strange, because with strace attached I occasionally see correct behaviour: [pid 23776] umount(/mnt/tmp-ums-test, 0) = 0 I need to debug the syscall in the kernel. Information about my system: x86_64: Linux 3.12.0 #2 SMP PREEMPT Wed Nov 27 10:26:22 CET 2013 x86_64 GNU/Linux Debian 7.4. Best regards, Wolfgang Denk -- Best regards, Lukasz Majewski Samsung RD Institute Poland (SRPOL) | Linux Platform Group ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
Dear Lukasz, In message 20141112152949.1fe6ce3c@amdc2363 you wrote: But this is a bug. Papering over is not a good idea. It should be analyzed, reported, and finally fixed. I've debugged the script with strace. Thanks a lot for that! The problem is with umount() syscall: ... I need to debug the syscall in the kernel. I have a gut feeling that this might be a problem somewhere with the USB stuff that is involved here. Maybe enabling some degug messages for the USB subsystem gives some more information? Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de The universe is all a spin-off of the Big Bang. ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
On 11/12/2014 09:45 AM, Wolfgang Denk wrote: Dear Lukasz, In message 20141112152949.1fe6ce3c@amdc2363 you wrote: But this is a bug. Papering over is not a good idea. It should be analyzed, reported, and finally fixed. I've debugged the script with strace. Thanks a lot for that! The problem is with umount() syscall: ... I need to debug the syscall in the kernel. I have a gut feeling that this might be a problem somewhere with the USB stuff that is involved here. Maybe enabling some degug messages for the USB subsystem gives some more information? If this really is related to USB only, it may be worth asking on the linux-usb mailing list to see if anyone already unerstands the issue. Irrespective of all this though, even if there is a kernel issue and it can be fixed, I still think we should apply this patch, because the issue currently affects people. At the very least it will until some kernel fix is rolled out to everyone's distro, which will be a while no matter what. ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
On Wed, 12 Nov 2014 11:11:33 -0700 Stephen Warren swar...@wwwdotorg.org wrote: On 11/12/2014 09:45 AM, Wolfgang Denk wrote: Dear Lukasz, In message 20141112152949.1fe6ce3c@amdc2363 you wrote: But this is a bug. Papering over is not a good idea. It should be analyzed, reported, and finally fixed. I've debugged the script with strace. Thanks a lot for that! The problem is with umount() syscall: ... I need to debug the syscall in the kernel. I have a gut feeling that this might be a problem somewhere with the USB stuff that is involved here. Maybe enabling some degug messages for the USB subsystem gives some more information? If this really is related to USB only, it may be worth asking on the linux-usb mailing list to see if anyone already unerstands the issue. Frankly speaking, I'm personally curious why such things happen. I may look into the issue in my spare :-) time. In spite of this, I agree with Stephen: Irrespective of all this though, even if there is a kernel issue and it can be fixed, I still think we should apply this patch, because the issue currently affects people. At the very least it will until some kernel fix is rolled out to everyone's distro, which will be a while no matter what. +1 The problem seems to be with long time running linux. The error seems to be orthogonal to our u-boot's UMS work. ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot Best regards, Lukasz Majewski signature.asc Description: PGP signature ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
On 11/07/2014 06:05 AM, Lukasz Majewski wrote: This change helps to run script on machines with quite long uptime. Without this the following error emerges: File: ./dat_14M.img umount: /mnt/tmp-ums-test: device is busy. (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1)) TX: md5sum:083d3d22b542d3ecba61b12d17e03f9f mount: /dev/sdd6 already mounted or /mnt/tmp-ums-test busy mount: according to mtab, /dev/sdd6 is already mounted on /mnt/tmp-ums-test Reviewed-by: Stephen Warren swar...@nvidia.com ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
On Friday, November 07, 2014 at 02:05:55 PM, Lukasz Majewski wrote: This change helps to run script on machines with quite long uptime. Without this the following error emerges: File: ./dat_14M.img umount: /mnt/tmp-ums-test: device is busy. (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1)) TX: md5sum:083d3d22b542d3ecba61b12d17e03f9f mount: /dev/sdd6 already mounted or /mnt/tmp-ums-test busy mount: according to mtab, /dev/sdd6 is already mounted on /mnt/tmp-ums-test Signed-off-by: Lukasz Majewski l.majew...@samsung.com Why exactly does mount not block until it can unmount the device anyway ? Best regards, Marek Vasut ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
Hi Marek, On Friday, November 07, 2014 at 02:05:55 PM, Lukasz Majewski wrote: This change helps to run script on machines with quite long uptime. Without this the following error emerges: File: ./dat_14M.img umount: /mnt/tmp-ums-test: device is busy. (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1)) TX: md5sum:083d3d22b542d3ecba61b12d17e03f9f mount: /dev/sdd6 already mounted or /mnt/tmp-ums-test busy mount: according to mtab, /dev/sdd6 is already mounted on /mnt/tmp-ums-test Signed-off-by: Lukasz Majewski l.majew...@samsung.com Why exactly does mount not block until it can unmount the device anyway ? Has mount or umount expose any blocking behavior? As fair as I remember you cannot umount directory when any process holds reference to it. Here it looks like process which copy data queues data for writing and exit from cp. Presumably, when we call umount there is still some pending data for write. Hence the error. Maybe there is a switch for mount/umount/cp which can correct such behavior? Best regards, Marek Vasut -- Best regards, Lukasz Majewski Samsung RD Institute Poland (SRPOL) | Linux Platform Group ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
On Friday, November 07, 2014 at 05:52:27 PM, Lukasz Majewski wrote: Hi Marek, On Friday, November 07, 2014 at 02:05:55 PM, Lukasz Majewski wrote: This change helps to run script on machines with quite long uptime. Without this the following error emerges: File: ./dat_14M.img umount: /mnt/tmp-ums-test: device is busy. (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1)) TX: md5sum:083d3d22b542d3ecba61b12d17e03f9f mount: /dev/sdd6 already mounted or /mnt/tmp-ums-test busy mount: according to mtab, /dev/sdd6 is already mounted on /mnt/tmp-ums-test Signed-off-by: Lukasz Majewski l.majew...@samsung.com Why exactly does mount not block until it can unmount the device anyway ? Has mount or umount expose any blocking behavior? I would expect umount to be blocking by default in the first place. ie. umount /mnt/foo should wait until all data are synced on device under /mnt/foo and only then it should be unmounted. Can you check (with strace or something) what exact return value will the umount() syscall return when it does NOT unmount the mountpoint and returns to the shell ? Is it EBUSY ? As fair as I remember you cannot umount directory when any process holds reference to it. Here it looks like process which copy data queues data for writing and exit from cp. Presumably, when we call umount there is still some pending data for write. Hence the error. In case there are data which are not yet sync'd to the device, the umount() syscall should block until those data are written and return only after that. Why would it return -EBUSY ... hm ... Maybe there is a switch for mount/umount/cp which can correct such behavior? That should be the default ... Best regards, Marek Vasut ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
Dear Lukasz, In message 141536-9790-1-git-send-email-l.majew...@samsung.com you wrote: -umount $MNT_DIR +while true; do + umount $MNT_DIR /dev/null 21 + if [ $? -eq 0 ]; then + break + fi + printf $COLOUR_ORANGE\tSleeping to wait for umount...$COLOUR_DEFAULT\n + sleep 1 +done As Marek already pointed out, umount (both the command (8) and the syscall (2)) are supposed to be blocking (except for typical error cases like no permission, mountpoint does not exist, no file system mounted, etc.). If you really ever see the umount entering above loop, then there is some bug somewhere. It would be indeed interesting to see the strace log for such umount calls. Also, can you please add details about the exact execution environment (host system / architecture, kernel version, distro, and _especially_ which sort of USB driver is involved here. My gut feeling is that there might be some USB driver error involved here. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de If the hours are long enough and the pay is short enough, someone will say it's women's work. ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
On 11/07/2014 02:54 PM, Wolfgang Denk wrote: Dear Lukasz, In message 141536-9790-1-git-send-email-l.majew...@samsung.com you wrote: -umount $MNT_DIR +while true; do + umount $MNT_DIR /dev/null 21 + if [ $? -eq 0 ]; then + break + fi + printf $COLOUR_ORANGE\tSleeping to wait for umount...$COLOUR_DEFAULT\n + sleep 1 +done As Marek already pointed out, umount (both the command (8) and the syscall (2)) are supposed to be blocking (except for typical error cases like no permission, mountpoint does not exist, no file system mounted, etc.). If you really ever see the umount entering above loop, then there is some bug somewhere. It would be indeed interesting to see the strace log for such umount calls. Also, can you please add details about the exact execution environment (host system / architecture, kernel version, distro, and _especially_ which sort of USB driver is involved here. My gut feeling is that there might be some USB driver error involved here. Where I've seen this is writing to an SD card in a USB-based SD card reader. I have a fairly regular amd64 machine running Ubuntu. I put the loop above into my own scripts that mount an SD card, copy new data to it, and then immediately unmount it for the same reason that Lukasz made this patch; umount doesn't always unmount. I did this so long ago that I don't recall which Ubuntu version I had at the time, nor the kernel version. It was *probably* Ubuntu 10.04 or 12.10 though. Now I'm on 14.04, but have no idea if I still need the loop since it's already in place:-) ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH v2] test: ums: Add sleep before unmount directory
Dear Stephen, In message 545d40e1.2030...@wwwdotorg.org you wrote: My gut feeling is that there might be some USB driver error involved here. Where I've seen this is writing to an SD card in a USB-based SD card reader. I have a fairly regular amd64 machine running Ubuntu. I put the loop above into my own scripts that mount an SD card, copy new data to it, and then immediately unmount it for the same reason that Lukasz made this patch; umount doesn't always unmount. I did this so long ago that I don't recall which Ubuntu version I had at the time, nor the kernel version. It was *probably* Ubuntu 10.04 or 12.10 though. Now I'm on 14.04, but have no idea if I still need the loop since it's already in place:-) But this is a bug. Papering over is not a good idea. It should be analyzed, reported, and finally fixed. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de Our management frequently gets lost in thought. That's because it's unfamiliar territory. ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
