# git rev-parse -q --verify 2be7d348fe924f0c5583c6a805bd42cecda93104^{commit} 2be7d348fe924f0c5583c6a805bd42cecda93104 already have revision, skipping fetch # git checkout -q -f -B kisskb 2be7d348fe924f0c5583c6a805bd42cecda93104 # git clean -qxdf # < git log -1 # commit 2be7d348fe924f0c5583c6a805bd42cecda93104 # Author: Linus Torvalds # Date: Tue Nov 26 11:34:06 2019 -0800 # # Revert "vfs: properly and reliably lock f_pos in fdget_pos()" # # This reverts commit 0be0ee71816b2b6725e2b4f32ad6726c9d729777. # # I was hoping it would be benign to switch over entirely to FMODE_STREAM, # and we'd have just a couple of small fixups we'd need, but it looks like # we're not quite there yet. # # While it worked fine on both my desktop and laptop, they are fairly # similar in other respects, and run mostly the same loads. Kenneth # Crudup reports that it seems to break both his vmware installation and # the KDE upower service. In both cases apparently leading to timeouts # due to waitinmg for the f_pos lock. # # There are a number of character devices in particular that definitely # want stream-like behavior, but that currently don't get marked as # streams, and as a result get the exclusion between concurrent # read()/write() on the same file descriptor. Which doesn't work well for # them. # # The most obvious example if this is /dev/console and /dev/tty, which use # console_fops and tty_fops respectively (and ptmx_fops for the pty master # side). It may be that it's just this that causes problems, but we # clearly weren't ready yet. # # Because there's a number of other likely common cases that don't have # llseek implementations and would seem to act as stream devices: # # /dev/fuse (fuse_dev_operations) # /dev/mcelog (mce_chrdev_ops) # /dev/mei0 (mei_fops) # /dev/net/tun (tun_fops) # /dev/nvme0 (nvme_dev_fops) # /dev/tpm0 (tpm_fops) # /proc/self/ns/mnt (ns_file_operations) # /dev/snd/pcm* (snd_pcm_f_ops[]) # # and while some of these could be trivially automatically detected by the # vfs layer when the character device is opened by just noticing that they # have no read or write operations either, it often isn't that obvious. # # Some character devices most definitely do use the file position, even if # they don't allow seeking: the firmware update code, for example, uses # simple_read_from_buffer() that does use f_pos, but doesn't allow seeking # back and forth. # # We'll revisit this when there's a better way to detect the problem and # fix it (possibly with a coccinelle script to do more of the FMODE_STREAM # annotations). # # Reported-by: Kenneth R. Crudup # Cc: Kirill Smelkov # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/br-mipsel-o32-full-2016.08-613-ge98b4dd/bin/mipsel-linux-gcc --version # < /opt/cross/kisskb/br-mipsel-o32-full-2016.08-613-ge98b4dd/bin/mipsel-linux-ld --version # < git log --format=%s --max-count=1 2be7d348fe924f0c5583c6a805bd42cecda93104 # < make -s -j 32 ARCH=mips O=/kisskb/build/linus_mips-defconfig_mipsel CROSS_COMPILE=/opt/cross/kisskb/br-mipsel-o32-full-2016.08-613-ge98b4dd/bin/mipsel-linux- defconfig # make -s -j 32 ARCH=mips O=/kisskb/build/linus_mips-defconfig_mipsel CROSS_COMPILE=/opt/cross/kisskb/br-mipsel-o32-full-2016.08-613-ge98b4dd/bin/mipsel-linux- FIT description: Linux 5.4.0-g2be7d348fe92 Created: Wed Nov 27 11:22:20 2019 Image 0 (kernel@0) Description: Linux 5.4.0-g2be7d348fe92 Created: Wed Nov 27 11:22:20 2019 Type: Kernel Image Compression: gzip compressed Data Size: 4784150 Bytes = 4672.02 KiB = 4.56 MiB Architecture: MIPS OS: Linux Load Address: 0x80100000 Entry Point: 0x808d01b0 Hash algo: sha1 Hash value: 80db1884a4dc06d172e75749832c056ac83197f6 Image 1 (fdt@boston) Description: img,boston Device Tree Created: Wed Nov 27 11:22:20 2019 Type: Flat Device Tree Compression: uncompressed Data Size: 3793 Bytes = 3.70 KiB = 0.00 MiB Architecture: MIPS Hash algo: sha1 Hash value: 4799f50d688573234da6e9d7701234d394759ef4 Image 2 (fdt@ni169445) Description: NI 169445 device tree Created: Wed Nov 27 11:22:20 2019 Type: Flat Device Tree Compression: uncompressed Data Size: 1871 Bytes = 1.83 KiB = 0.00 MiB Architecture: MIPS Hash algo: sha1 Hash value: 51b89b31605ee62038c8468c429af091dfc75ec7 Image 3 (fdt@ocelot_pcb123) Description: MSCC Ocelot PCB123 Device Tree Created: Wed Nov 27 11:22:20 2019 Type: Flat Device Tree Compression: uncompressed Data Size: 4639 Bytes = 4.53 KiB = 0.00 MiB Architecture: MIPS Hash algo: sha1 Hash value: 018897896b42c41c943aca35a20e4300dba250c8 Image 4 (fdt@ocelot_pcb120) Description: MSCC Ocelot PCB120 Device Tree Created: Wed Nov 27 11:22:20 2019 Type: Flat Device Tree Compression: uncompressed Data Size: 5198 Bytes = 5.08 KiB = 0.00 MiB Architecture: MIPS Hash algo: sha1 Hash value: 36c7bd0bd79cfc2f7dd6acda6c7996294f4967e6 Image 5 (fdt@xilfpga) Description: MIPSfpga (xilfpga) Device Tree Created: Wed Nov 27 11:22:20 2019 Type: Flat Device Tree Compression: uncompressed Data Size: 2708 Bytes = 2.64 KiB = 0.00 MiB Architecture: MIPS Hash algo: sha1 Hash value: 63d058b780f65e22da30f0a183433765f1807f1d Default Configuration: 'conf@default' Configuration 0 (conf@default) Description: Generic Linux kernel Kernel: kernel@0 Configuration 1 (conf@boston) Description: Boston Linux kernel Kernel: kernel@0 FDT: fdt@boston Configuration 2 (conf@ni169445) Description: NI 169445 Linux Kernel Kernel: kernel@0 FDT: fdt@ni169445 Configuration 3 (conf@ocelot_pcb123) Description: Ocelot Linux kernel Kernel: kernel@0 FDT: fdt@ocelot_pcb123 Configuration 4 (conf@ocelot_pcb120) Description: Ocelot Linux kernel Kernel: kernel@0 FDT: fdt@ocelot_pcb120 Configuration 5 (conf@xilfpga) Description: MIPSfpga Linux kernel Kernel: kernel@0 FDT: fdt@xilfpga Completed OK # rm -rf /kisskb/build/linus_mips-defconfig_mipsel # Build took: 0:01:58.988617