# 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/gcc-4.6.3-nolibc/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi-gcc --version # < /opt/cross/kisskb/gcc-4.6.3-nolibc/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi-ld --version # < git log --format=%s --max-count=1 2be7d348fe924f0c5583c6a805bd42cecda93104 # < make -s -j 8 ARCH=arm O=/kisskb/build/linus_dove_defconfig_arm CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi- dove_defconfig # make -s -j 8 ARCH=arm O=/kisskb/build/linus_dove_defconfig_arm CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi- /kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl': /kisskb/src/kernel/printk/printk.c:204:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/crypto/sha512_generic.c: In function 'sha512_transform': /kisskb/src/crypto/sha512_generic.c:149:1: warning: the frame size of 1184 bytes is larger than 1024 bytes [-Wframe-larger-than=] /kisskb/src/drivers/base/regmap/regmap.c: In function 'regmap_raw_read': /kisskb/src/drivers/base/regmap/regmap.c:2591:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/base/regmap/regmap.c: In function '_regmap_raw_write': /kisskb/src/drivers/base/regmap/regmap.c:1852:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/proc/inode.c: In function 'proc_reg_open': /kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/proc/inode.c:338:21: note: 'pdeo' was declared here /kisskb/src/fs/udf/unicode.c: In function 'udf_name_conv_char': /kisskb/src/fs/udf/unicode.c:132:8: warning: 'c' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/usb/core/devio.c: In function 'async_completed': /kisskb/src/drivers/usb/core/devio.c:625:23: warning: 'errno' may be used uninitialized in this function [-Wuninitialized] WARNING: "return_address" [vmlinux] is a static EXPORT_SYMBOL_GPL Completed OK # rm -rf /kisskb/build/linus_dove_defconfig_arm # Build took: 0:01:54.126538