# git rev-parse -q --verify 4b820e167bf6f410ace479d8df5b15a574000e75^{commit}
4b820e167bf6f410ace479d8df5b15a574000e75
already have revision, skipping fetch
# git checkout -q -f -B kisskb 4b820e167bf6f410ace479d8df5b15a574000e75
# git clean -qxdf
# < git log -1
# commit 4b820e167bf6f410ace479d8df5b15a574000e75
# Author: Linus Torvalds <torvalds@linux-foundation.org>
# Date:   Fri Jul 2 22:05:52 2021 -0700
# 
#     Revert "ALSA: usb-audio: Reduce latency at playback start"
#     
#     This reverts commit 9ce650a75a3b262c90789b42aedee8fc2ee04d53.
#     
#     This commit causes watchdog lockups on my machine, and while I have no
#     idea what the cause is, it bisected right to this commit, and reverting
#     the change promptly fixes it.
#     
#     At least occasionally one of the watchdog call traces was
#     
#       Call Trace:
#         _raw_spin_lock_irqsave+0x35/0x40
#         snd_pcm_period_elapsed+0x1b/0xa0 [snd_pcm]
#         snd_usb_endpoint_start+0x1a0/0x3c0 [snd_usb_audio]
#         start_endpoints+0x23/0x90 [snd_usb_audio]
#         snd_usb_substream_playback_trigger+0x7b/0x1a0 [snd_usb_audio]
#         snd_pcm_common_ioctl+0x1c44/0x2360 [snd_pcm]
#         snd_pcm_ioctl+0x2e/0x40 [snd_pcm]
#         __se_sys_ioctl+0x72/0xc0
#         do_syscall_64+0x4c/0xa0
#         entry_SYSCALL_64_after_hwframe+0x44/0xae
#     
#     so presumably it's a locking error on that substream spinlock that
#     snd_pcm_period_elapsed() takes.  But at this point I just want to have a
#     working system so that I can continue the merge window work tomorrow.
#     
#     Cc: Takashi Iwai <tiwai@suse.de>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-ld --version
# < git log --format=%s --max-count=1 4b820e167bf6f410ace479d8df5b15a574000e75
# < make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-  m5272c3_defconfig
# < make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-  help
# make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-  olddefconfig
# make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-  
In file included from /kisskb/src/mm/vmscan.c:33:
/kisskb/src/mm/vmscan.c: In function 'shrink_page_list':
/kisskb/src/include/linux/rmap.h:294:34: warning: statement with no effect [-Wunused-value]
 #define try_to_unmap(page, refs) false
                                  ^~~~~
/kisskb/src/mm/vmscan.c:1502:4: note: in expansion of macro 'try_to_unmap'
    try_to_unmap(page, flags);
    ^~~~~~~~~~~~
Completed OK
# rm -rf /kisskb/build/linus_m5272c3_defconfig_m68k-gcc8
# Build took: 0:00:31.177335