# 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 <torvalds@linux-foundation.org>
# 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 <kenny@panix.com>
#     Cc: Kirill Smelkov <kirr@nexedi.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-ld --version
# < git log --format=%s --max-count=1 2be7d348fe924f0c5583c6a805bd42cecda93104
# < make -s -j 10 ARCH=sh O=/kisskb/build/linus_se7724_defconfig_sh4 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-  se7724_defconfig
# make -s -j 10 ARCH=sh O=/kisskb/build/linus_se7724_defconfig_sh4 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-  
  Generating include/generated/machtypes.h
<stdin>:1511:2: warning: #warning syscall clone3 not implemented [-Wcpp]
/kisskb/src/arch/sh/kernel/cpu/sh4/../sh3/../../entry-common.S: Assembler messages:
/kisskb/src/arch/sh/kernel/cpu/sh4/../sh3/../../entry-common.S:385: Warning: overflow in branch to syscall_exit_work; converted into longer instruction sequence
/kisskb/src/arch/sh/kernel/cpu/sh4/../sh3/../../entry-common.S:388: Warning: overflow in branch to syscall_exit_work; converted into longer instruction sequence
/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/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/kernel/rcu/srcutree.c: In function 'init_srcu_struct_fields':
/kisskb/src/kernel/rcu/srcutree.c:121:34: warning: 'levelspread[<Uc6e0>]' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c:88:6: note: 'levelspread[<Uc6e0>]' was declared here
/kisskb/src/sound/soc/soc-pcm.c: In function 'dpcm_be_connect':
/kisskb/src/sound/soc/soc-pcm.c:1149:8: warning: unused variable 'name' [-Wunused-variable]
/kisskb/src/drivers/i2c/busses/i2c-sh_mobile.c: In function 'sh_mobile_i2c_isr':
/kisskb/src/drivers/i2c/busses/i2c-sh_mobile.c:399:26: warning: 'data' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/i2c/busses/i2c-sh_mobile.c:372:16: note: 'data' was declared here
/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/drivers/sh/clk/cpg.c: In function 'r8':
/kisskb/src/drivers/sh/clk/cpg.c:41:2: warning: passing argument 1 of 'ioread8' discards 'const' qualifier from pointer target type [enabled by default]
/kisskb/src/include/asm-generic/iomap.h:29:21: note: expected 'void *' but argument is of type 'const void *'
/kisskb/src/drivers/sh/clk/cpg.c: In function 'r16':
/kisskb/src/drivers/sh/clk/cpg.c:46:2: warning: passing argument 1 of 'ioread16' discards 'const' qualifier from pointer target type [enabled by default]
/kisskb/src/include/asm-generic/iomap.h:30:21: note: expected 'void *' but argument is of type 'const void *'
/kisskb/src/drivers/sh/clk/cpg.c: In function 'r32':
/kisskb/src/drivers/sh/clk/cpg.c:51:2: warning: passing argument 1 of 'ioread32' discards 'const' qualifier from pointer target type [enabled by default]
/kisskb/src/include/asm-generic/iomap.h:32:21: note: expected 'void *' but argument is of type 'const void *'
/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]
Image Name:   Linux-5.4.0+
Created:      Wed Nov 27 11:16:36 2019
Image Type:   SuperH Linux Kernel Image (gzip compressed)
Data Size:    3397835 Bytes = 3318.20 KiB = 3.24 MiB
Load Address: 88001000
Entry Point:  88002000
  Image arch/sh/boot/uImage is ready
Completed OK
# rm -rf /kisskb/build/linus_se7724_defconfig_sh4
# Build took: 0:00:51.406656