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android_kernel_asus_sm8350/kernel
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Steven Rostedt (Google) cf221a7880 ring-buffer: Update "shortest_full" in polling 
commit 1e0cb399c7653462d9dadf8ab9425337c355d358 upstream.

It was discovered that the ring buffer polling was incorrectly stating
that read would not block, but that's because polling did not take into
account that reads will block if the "buffer-percent" was set. Instead,
the ring buffer polling would say reads would not block if there was any
data in the ring buffer. This was incorrect behavior from a user space
point of view. This was fixed by commit 42fb0a1e84ff by having the polling
code check if the ring buffer had more data than what the user specified
"buffer percent" had.

The problem now is that the polling code did not register itself to the
writer that it wanted to wait for a specific "full" value of the ring
buffer. The result was that the writer would wake the polling waiter
whenever there was a new event. The polling waiter would then wake up, see
that there's not enough data in the ring buffer to notify user space and
then go back to sleep. The next event would wake it up again.

Before the polling fix was added, the code would wake up around 100 times
for a hackbench 30 benchmark. After the "fix", due to the constant waking
of the writer, it would wake up over 11,0000 times! It would never leave
the kernel, so the user space behavior was still "correct", but this
definitely is not the desired effect.

To fix this, have the polling code add what it's waiting for to the
"shortest_full" variable, to tell the writer not to wake it up if the
buffer is not as full as it expects to be.

Note, after this fix, it appears that the waiter is now woken up around 2x
the times it was before (~200). This is a tremendous improvement from the
11,000 times, but I will need to spend some time to see why polling is
more aggressive in its wakeups than the read blocking code.

Link: https://lore.kernel.org/linux-trace-kernel/20230929180113.01c2cae3@rorschach.local.home

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Fixes: 42fb0a1e84ff ("tracing/ring-buffer: Have polling block on watermark")
Reported-by: Julia Lawall <julia.lawall@inria.fr>
Tested-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-10-10 21:46:41 +02:00
..
bpf bpf: Avoid deadlock when using queue and stack maps from NMI 2023-10-10 21:46:36 +02:00
cgroup cgroup: Do not corrupt task iteration when rebinding subsystem 2023-06-28 10:18:36 +02:00
configs
debug treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD() 2023-04-20 12:07:32 +02:00
dma treewide: Remove uninitialized_var() usage 2023-06-09 10:29:01 +02:00
events perf: Fix function pointer case 2023-08-11 11:53:54 +02:00
gcov gcov: add support for checksum field 2023-01-18 11:41:42 +01:00
irq genirq: Add IRQF_NO_AUTOEN for request_irq/nmi() 2023-05-17 11:35:46 +02:00
livepatch livepatch: fix race between fork and KLP transition 2022-10-26 13:22:18 +02:00
locking treewide: Remove uninitialized_var() usage 2023-06-09 10:29:01 +02:00
power PM: hibernate: Fix mistake in kerneldoc comment 2023-01-18 11:40:53 +01:00
printk printk: fix return value of printk.devkmsg __setup handler 2022-04-15 14:18:08 +02:00
rcu rcu: Suppress smp_processor_id() complaint in synchronize_rcu_expedited_wait() 2023-03-11 16:43:54 +01:00
sched sched/fair: Don't balance task to its current running CPU 2023-07-27 08:37:42 +02:00
time posix-timers: Ensure timer ID search-loop limit is valid 2023-07-27 08:37:42 +02:00
trace ring-buffer: Update "shortest_full" in polling 2023-10-10 21:46:41 +02:00
.gitignore kbuild: update config_data.gz only when the content of .config is changed 2021-05-11 14:04:16 +02:00
acct.c acct: fix potential integer overflow in encode_comp_t() 2023-01-18 11:41:34 +01:00
async.c treewide: Remove uninitialized_var() usage 2023-06-09 10:29:01 +02:00
audit_fsnotify.c audit: fix potential double free on error path from fsnotify_add_inode_mark 2022-09-05 10:27:38 +02:00
audit_tree.c audit: move put_tree() to avoid trim_trees refcount underflow and UAF 2021-09-03 10:08:16 +02:00
audit_watch.c audit: CONFIG_CHANGE don't log internal bookkeeping as an event 2020-10-01 13:17:32 +02:00
audit.c treewide: Remove uninitialized_var() usage 2023-06-09 10:29:01 +02:00
audit.h audit: log AUDIT_TIME_* records only from rules 2022-04-15 14:18:04 +02:00
auditfilter.c audit: fix a net reference leak in audit_list_rules_send() 2020-06-22 09:30:59 +02:00
auditsc.c audit: fix possible soft lockup in __audit_inode_child() 2023-09-23 10:59:46 +02:00
backtracetest.c treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD() 2023-04-20 12:07:32 +02:00
bounds.c
capability.c
compat.c sched_getaffinity: don't assume 'cpumask_size()' is fully initialized 2023-04-05 11:16:42 +02:00
configs.c kernel/configs: Replace GPL boilerplate code with SPDX identifier 2019-07-30 18:34:15 +02:00
context_tracking.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
cpu_pm.c kernel/cpu_pm: Fix uninitted local in cpu_pm 2020-06-22 09:31:22 +02:00
cpu.c random: clear fast pool, crng, and batches in cpuhp bring up 2022-06-22 14:11:12 +02:00
crash_core.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230 2019-06-19 17:09:06 +02:00
crash_dump.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
cred.c keys: Fix request_key() cache 2020-01-17 19:48:42 +01:00
delayacct.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 25 2019-05-21 11:52:39 +02:00
dma.c
exec_domain.c
exit.c treewide: Remove uninitialized_var() usage 2023-06-09 10:29:01 +02:00
extable.c kernel/extable.c: use address-of operator on section symbols 2023-06-09 10:29:01 +02:00
fail_function.c kernel/fail_function: fix memory leak with using debugfs_lookup() 2023-03-11 16:44:15 +01:00
fork.c kernel/fork: beware of __put_task_struct() calling context 2023-09-23 11:00:03 +02:00
freezer.c Revert "libata, freezer: avoid block device removal while system is frozen" 2019-10-06 09:11:37 -06:00
futex.c treewide: Remove uninitialized_var() usage 2023-06-09 10:29:01 +02:00
gen_kheaders.sh kbuild: add variables for compression tools 2020-09-03 11:27:10 +02:00
groups.c
hung_task.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
iomem.c mm/nvdimm: add is_ioremap_addr and use that to check ioremap address 2019-07-12 11:05:40 -07:00
irq_work.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
jump_label.c jump_label: Don't warn on __exit jump entries 2019-08-29 15:10:10 +01:00
kallsyms.c kallsyms: Refactor kallsyms_show_value() to take cred 2020-07-16 08:16:44 +02:00
kcmp.c exec: Transform exec_update_mutex into a rw_semaphore 2021-01-09 13:44:55 +01:00
Kconfig.freezer treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig.hz treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig.locks treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig.preempt sched/rt, Kconfig: Unbreak def/oldconfig with CONFIG_PREEMPT=y 2019-07-22 18:05:11 +02:00
kcov.c
kexec_core.c kexec: fix a memory leak in crash_shrink_memory() 2023-07-27 08:37:10 +02:00
kexec_elf.c kexec_elf: support 32 bit ELF files 2019-09-06 23:58:44 +02:00
kexec_file.c kexec: support purgatories with .text.hot sections 2023-06-21 15:44:10 +02:00
kexec_internal.h
kexec.c kexec_load: Disable at runtime if the kernel is locked down 2019-08-19 21:54:15 -07:00
kheaders.c kheaders: Use array declaration instead of char 2023-05-17 11:35:33 +02:00
kmod.c kmod: make request_module() return an error when autoloading is disabled 2020-04-17 10:50:22 +02:00
kprobes.c x86/kprobes: Fix arch_check_optimized_kprobe check within optimized_kprobe range 2023-03-11 16:44:02 +01:00
ksysfs.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 170 2019-05-30 11:26:39 -07:00
kthread.c kthread: Fix PF_KTHREAD vs to_kthread() race 2021-09-12 08:56:39 +02:00
latencytop.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
Makefile kbuild: update config_data.gz only when the content of .config is changed 2021-05-11 14:04:16 +02:00
module_signature.c module: harden ELF info handling 2021-04-07 14:47:38 +02:00
module_signing.c module: harden ELF info handling 2021-04-07 14:47:38 +02:00
module-internal.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
module.c modules: only allow symbol_get of EXPORT_SYMBOL_GPL modules 2023-09-23 10:59:36 +02:00
notifier.c kernel/notifier.c: intercept duplicate registrations to avoid infinite loops 2020-10-01 13:17:23 +02:00
nsproxy.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
padata.c padata: add separate cpuhp node for CPUHP_PADATA_DEAD 2020-06-17 16:40:22 +02:00
panic.c exit: Use READ_ONCE() for all oops/warn limit reads 2023-02-06 07:52:50 +01:00
params.c lockdown: Lock down module params that specify hardware parameters (eg. ioport) 2019-08-19 21:54:16 -07:00
pid_namespace.c memcg: enable accounting for pids in nested pid namespaces 2021-09-22 12:26:37 +02:00
pid.c kernel/pid.c: convert struct pid count to refcount_t 2019-07-16 19:23:24 -07:00
profile.c profiling: fix shift too large makes kernel panic 2022-08-25 11:18:02 +02:00
ptrace.c ptrace: Reimplement PTRACE_KILL by always sending SIGKILL 2022-06-14 18:11:24 +02:00
range.c
reboot.c reboot: fix overflow parsing reboot cpu number 2020-11-18 19:20:30 +01:00
relay.c relayfs: fix out-of-bounds access in relay_file_read 2023-05-17 11:35:58 +02:00
resource.c /dev/mem: Revoke mappings when a driver claims the region 2020-06-24 17:50:35 +02:00
rseq.c signal: Remove task parameter from force_sig 2019-05-27 09:36:28 -05:00
seccomp.c seccomp: Invalidate seccomp mode to catch death failures 2022-02-16 12:52:53 +01:00
signal.c signal handling: don't use BUG_ON() for debugging 2022-07-21 20:59:27 +02:00
smp.c smp: Fix offline cpu check in flush_smp_call_function_queue() 2022-04-20 09:19:39 +02:00
smpboot.c kthread: Extract KTHREAD_IS_PER_CPU 2021-02-07 15:35:49 +01:00
smpboot.h
softirq.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 11:01:13 -07:00
stackleak.c
stacktrace.c stacktrace: Don't skip first entry on noncurrent tasks 2019-11-04 21:19:25 +01:00
stop_machine.c stop_machine: Avoid potential race behaviour 2019-10-17 12:47:12 +02:00
sys_ni.c kernel/sys_ni: add compat entry for fadvise64_64 2022-09-05 10:27:38 +02:00
sys.c prlimit: do_prlimit needs to have a speculation check 2023-01-24 07:17:59 +01:00
sysctl_binary.c
sysctl-test.c kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec() 2020-10-01 13:17:10 +02:00
sysctl.c mm: allow a controlled amount of unfairness in the page lock 2023-08-30 16:27:26 +02:00
task_work.c
taskstats.c taskstats: fix data-race 2020-01-09 10:19:54 +01:00
test_kprobes.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 25 2019-05-21 11:52:39 +02:00
torture.c torture: Remove exporting of internal functions 2019-08-01 14:30:22 -07:00
tracepoint.c tracepoint: Add tracepoint_probe_register_may_exist() for BPF tracing 2021-07-14 16:53:08 +02:00
tsacct.c taskstats: Cleanup the use of task->exit_code 2022-02-23 11:59:57 +01:00
ucount.c proc/sysctl: add shared variables for range check 2019-07-18 17:08:07 -07:00
uid16.c
uid16.h
umh.c usermodehelper: reset umask to default before executing user process 2020-10-14 10:32:58 +02:00
up.c smp: Fix smp_call_function_single_async prototype 2021-05-14 09:44:33 +02:00
user_namespace.c Keyrings namespacing 2019-07-08 19:36:47 -07:00
user-return-notifier.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
user.c Keyrings namespacing 2019-07-08 19:36:47 -07:00
utsname_sysctl.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
utsname.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
watchdog_hld.c watchdog/perf: more properly prevent false positives with turbo modes 2023-07-27 08:37:10 +02:00
watchdog.c watchdog: export lockup_detector_reconfigure 2022-08-25 11:18:37 +02:00
workqueue_internal.h sched/core, workqueues: Distangle worker accounting from rq lock 2019-04-16 16:55:15 +02:00
workqueue.c workqueue: clean up WORK_* constant types, clarify masking 2023-07-27 08:37:29 +02:00