# git rev-parse -q --verify fa4b851b4ad632dc673627f38a8a552547568a2c^{commit}
fa4b851b4ad632dc673627f38a8a552547568a2c
already have revision, skipping fetch
# git checkout -q -f -B kisskb fa4b851b4ad632dc673627f38a8a552547568a2c
# git clean -qxdf
# < git log -1
# commit fa4b851b4ad632dc673627f38a8a552547568a2c
# Merge: 210ee636c4ad e5d7c1916562
# Author: Linus Torvalds <torvalds@linux-foundation.org>
# Date:   Sun Mar 10 11:53:21 2024 -0700
# 
#     Merge tag 'trace-ring-buffer-v6.8-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
#     
#     Pull tracing fixes from Steven Rostedt:
#     
#      - Do not allow large strings (> 4096) as single write to trace_marker
#     
#        The size of a string written into trace_marker was determined by the
#        size of the sub-buffer in the ring buffer. That size is dependent on
#        the PAGE_SIZE of the architecture as it can be mapped into user
#        space. But on PowerPC, where PAGE_SIZE is 64K, that made the limit of
#        the string of writing into trace_marker 64K.
#     
#        One of the selftests looks at the size of the ring buffer sub-buffers
#        and writes that plus more into the trace_marker. The write will take
#        what it can and report back what it consumed so that the user space
#        application (like echo) will write the rest of the string. The string
#        is stored in the ring buffer and can be read via the "trace" or
#        "trace_pipe" files.
#     
#        The reading of the ring buffer uses vsnprintf(), which uses a
#        precision "%.*s" to make sure it only reads what is stored in the
#        buffer, as a bug could cause the string to be non terminated.
#     
#        With the combination of the precision change and the PAGE_SIZE of 64K
#        allowing huge strings to be added into the ring buffer, plus the test
#        that would actually stress that limit, a bug was reported that the
#        precision used was too big for "%.*s" as the string was close to 64K
#        in size and the max precision of vsnprintf is 32K.
#     
#        Linus suggested not to have that precision as it could hide a bug if
#        the string was again stored without a nul byte.
#     
#        Another issue that was brought up is that the trace_seq buffer is
#        also based on PAGE_SIZE even though it is not tied to the
#        architecture limit like the ring buffer sub-buffer is. Having it be
#        64K * 2 is simply just too big and wasting memory on systems with 64K
#        page sizes. It is now hardcoded to 8K which is what all other
#        architectures with 4K PAGE_SIZE has.
#     
#        Finally, the write to trace_marker is now limited to 4K as there is
#        no reason to write larger strings into trace_marker.
#     
#      - ring_buffer_wait() should not loop.
#     
#        The ring_buffer_wait() does not have the full context (yet) on if it
#        should loop or not. Just exit the loop as soon as its woken up and
#        let the callers decide to loop or not (they already do, so it's a bit
#        redundant).
#     
#      - Fix shortest_full field to be the smallest amount in the ring buffer
#        that a waiter is waiting for. The "shortest_full" field is updated
#        when a new waiter comes in and wants to wait for a smaller amount of
#        data in the ring buffer than other waiters. But after all waiters are
#        woken up, it's not reset, so if another waiter comes in wanting to
#        wait for more data, it will be woken up when the ring buffer has a
#        smaller amount from what the previous waiters were waiting for.
#     
#      - The wake up all waiters on close is incorrectly called frome
#        .release() and not from .flush() so it will never wake up any waiters
#        as the .release() will not get called until all .read() calls are
#        finished. And the wakeup is for the waiters in those .read() calls.
#     
#     * tag 'trace-ring-buffer-v6.8-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
#       tracing: Use .flush() call to wake up readers
#       ring-buffer: Fix resetting of shortest_full
#       ring-buffer: Fix waking up ring buffer readers
#       tracing: Limit trace_marker writes to just 4K
#       tracing: Limit trace_seq size to just 8K and not depend on architecture PAGE_SIZE
#       tracing: Remove precision vsnprintf() check from print event
# < /opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-ld --version
# < git log --format=%s --max-count=1 fa4b851b4ad632dc673627f38a8a552547568a2c
# make -s -j 160 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-  x86_64_defconfig
# < make -s -j 160 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-  help
# make -s -j 160 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-  olddefconfig
# make -s -j 160 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-  
Completed OK
# rm -rf /kisskb/build/linus_x86_64_defconfig_x86_64-gcc8
# Build took: 0:01:48.250808