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307f56f260
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Steven Rostedt (Google) 307f56f260 ring-buffer: Remove useless update to write_stamp in rb_try_to_discard() 
[ Upstream commit 083e9f65bd ]

When filtering is enabled, a temporary buffer is created to place the
content of the trace event output so that the filter logic can decide
from the trace event output if the trace event should be filtered out or
not. If it is to be filtered out, the content in the temporary buffer is
simply discarded, otherwise it is written into the trace buffer.

But if an interrupt were to come in while a previous event was using that
temporary buffer, the event written by the interrupt would actually go
into the ring buffer itself to prevent corrupting the data on the
temporary buffer. If the event is to be filtered out, the event in the
ring buffer is discarded, or if it fails to discard because another event
were to have already come in, it is turned into padding.

The update to the write_stamp in the rb_try_to_discard() happens after a
fix was made to force the next event after the discard to use an absolute
timestamp by setting the before_stamp to zero so it does not match the
write_stamp (which causes an event to use the absolute timestamp).

But there's an effort in rb_try_to_discard() to put back the write_stamp
to what it was before the event was added. But this is useless and
wasteful because nothing is going to be using that write_stamp for
calculations as it still will not match the before_stamp.

Remove this useless update, and in doing so, we remove another
cmpxchg64()!

Also update the comments to reflect this change as well as remove some
extra white space in another comment.

Link: https://lore.kernel.org/linux-trace-kernel/20231215081810.1f4f38fe@rorschach.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Vincent Donnefort   <vdonnefort@google.com>
Fixes: b2dd797543 ("ring-buffer: Force absolute timestamp on discard of event")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-01-01 12:42:44 +00:00
..
bpf bpf: Fix prog_array_map_poke_run map poke update 2024-01-01 12:42:23 +00:00
cgroup cgroup_freezer: cgroup_freezing: Check if not frozen 2023-12-13 18:45:22 +01:00
configs Kbuild updates for v6.6 2023-09-05 11:01:47 -07:00
debug kgdb: Flush console before entering kgdb on panic 2023-11-28 17:19:47 +00:00
dma swiotlb: fix out-of-bounds TLB allocations with CONFIG_SWIOTLB_DYNAMIC 2023-11-28 17:20:13 +00:00
entry entry: Remove empty addr_limit_user_check() 2023-08-23 10:32:39 +02:00
events perf: Fix perf_event_validate_size() lockdep splat 2023-12-20 17:02:01 +01:00
futex futex: Don't include process MM in futex key on no-MMU 2023-11-20 11:58:53 +01:00
gcov gcov: shut up missing prototype warnings for internal stubs 2023-08-18 10:18:58 -07:00
irq genirq/generic_chip: Make irq_remove_generic_chip() irqdomain aware 2023-11-28 17:19:59 +00:00
kcsan kcsan: Don't expect 64 bits atomic builtins from 32 bits architectures 2023-06-09 23:29:50 +10:00
livepatch livepatch: Fix missing newline character in klp_resolve_symbols() 2023-11-20 11:59:25 +01:00
locking lockdep: Fix block chain corruption 2023-12-03 07:33:06 +01:00
module module/decompress: use kvmalloc() consistently 2023-11-20 11:59:37 +01:00
power PM: hibernate: Clean up sync_read handling in snapshot_write_next() 2023-11-28 17:20:02 +00:00
printk Merge branch 'rework/misc-cleanups' into for-linus 2023-10-11 12:58:14 +02:00
rcu rcu: kmemleak: Ignore kmemleak false positives when RCU-freeing objects 2023-11-28 17:20:02 +00:00
sched sched/fair: Fix the decision for load balance 2023-12-03 07:33:02 +01:00
time hrtimers: Push pending hrtimers away from outgoing CPU earlier 2023-12-13 18:44:56 +01:00
trace ring-buffer: Remove useless update to write_stamp in rb_try_to_discard() 2024-01-01 12:42:44 +00:00
.gitignore
acct.c audit/stable-6.6 PR 20230829 2023-08-30 08:17:35 -07:00
async.c
audit_fsnotify.c
audit_tree.c
audit_watch.c audit: don't WARN_ON_ONCE(!current->mm) in audit_exe_compare() 2023-11-28 17:19:56 +00:00
audit.c audit: move trailing statements to next line 2023-08-15 18:16:14 -04:00
audit.h audit: correct audit_filter_inodes() definition 2023-07-21 12:17:25 -04:00
auditfilter.c audit: move trailing statements to next line 2023-08-15 18:16:14 -04:00
auditsc.c audit,io_uring: io_uring openat triggers audit reference count underflow 2023-10-13 18:34:46 +02:00
backtracetest.c
bounds.c
capability.c lsm: constify the 'target' parameter in security_capget() 2023-08-08 16:48:47 -04:00
cfi.c
compat.c sched_getaffinity: don't assume 'cpumask_size()' is fully initialized 2023-03-14 19:32:38 -07:00
configs.c
context_tracking.c locking/atomic: treewide: use raw_atomic*_<op>() 2023-06-05 09:57:20 +02:00
cpu_pm.c cpuidle, cpu_pm: Remove RCU fiddling from cpu_pm_{enter,exit}() 2023-01-13 11:48:15 +01:00
cpu.c hrtimers: Push pending hrtimers away from outgoing CPU earlier 2023-12-13 18:44:56 +01:00
crash_core.c Crash: add lock to serialize crash hotplug handling 2023-09-29 17:20:48 -07:00
crash_dump.c
cred.c cred: get rid of CONFIG_DEBUG_CREDENTIALS 2023-12-20 17:01:51 +01:00
delayacct.c delayacct: track delays from IRQ/SOFTIRQ 2023-04-18 16:39:34 -07:00
dma.c
exec_domain.c
exit.c cred: get rid of CONFIG_DEBUG_CREDENTIALS 2023-12-20 17:01:51 +01:00
extable.c
fail_function.c kernel/fail_function: fix memory leak with using debugfs_lookup() 2023-02-08 13:36:22 +01:00
fork.c mm: add a NO_INHERIT flag to the PR_SET_MDWE prctl 2023-12-03 07:33:06 +01:00
freezer.c
gen_kheaders.sh Revert "kheaders: substituting --sort in archive creation" 2023-05-28 16:20:21 +09:00
groups.c
hung_task.c kernel/hung_task.c: set some hung_task.c variables storage-class-specifier to static 2023-04-08 13:45:37 -07:00
iomem.c kernel/iomem.c: remove __weak ioremap_cache helper 2023-08-21 13:37:28 -07:00
irq_work.c trace: Add trace_ipi_send_cpu() 2023-03-24 11:01:29 +01:00
jump_label.c jump_label: Prevent key->enabled int overflow 2022-12-01 15:53:05 -08:00
kallsyms_internal.h kallsyms: Reduce the memory occupied by kallsyms_seqs_of_names[] 2022-11-12 18:47:36 -08:00
kallsyms_selftest.c Modules changes for v6.6-rc1 2023-08-29 17:32:32 -07:00
kallsyms_selftest.h kallsyms: Add self-test facility 2022-11-15 00:42:02 -08:00
kallsyms.c kallsyms: Change func signature for cleanup_symbol_name() 2023-08-25 15:00:36 -07:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.kexec kexec: drop dependency on ARCH_SUPPORTS_KEXEC from CRASH_DUMP 2023-12-20 17:02:03 +01:00
Kconfig.locks
Kconfig.preempt
kcov.c kcov: add prototypes for helper functions 2023-06-09 17:44:17 -07:00
kexec_core.c crash: add generic infrastructure for crash hotplug support 2023-08-24 16:25:13 -07:00
kexec_elf.c
kexec_file.c integrity-v6.6 2023-08-30 09:16:56 -07:00
kexec_internal.h
kexec.c kernel: kexec: copy user-array safely 2023-11-28 17:19:40 +00:00
kheaders.c kheaders: Use array declaration instead of char 2023-03-24 20:10:59 -07:00
kprobes.c kprobes: consistent rcu api usage for kretprobe holder 2023-12-13 18:45:31 +01:00
ksyms_common.c kallsyms: make kallsyms_show_value() as generic function 2023-06-08 12:27:20 -07:00
ksysfs.c crash: hotplug support for kexec_load() 2023-08-24 16:25:14 -07:00
kthread.c kthread: unexport __kthread_should_park() 2023-08-18 10:18:59 -07:00
latencytop.c
Makefile v6.5-rc1-modules-next 2023-06-28 15:51:08 -07:00
module_signature.c
notifier.c notifiers: add tracepoints to the notifiers infrastructure 2023-04-08 13:45:38 -07:00
nsproxy.c nsproxy: Convert nsproxy.count to refcount_t 2023-08-21 11:29:12 -07:00
padata.c crypto: pcrypt - Fix hungtask for PADATA_RESET 2023-11-28 17:19:42 +00:00
panic.c panic: Reenable preemption in WARN slowpath 2023-09-15 11:28:08 +02:00
params.c kernel: params: Remove unnecessary ‘0’ values from err 2023-07-10 12:47:01 -07:00
pid_namespace.c memfd: replace ratcheting feature from vm.memfd_noexec with hierarchy 2023-08-21 13:37:59 -07:00
pid_sysctl.h memfd: replace ratcheting feature from vm.memfd_noexec with hierarchy 2023-08-21 13:37:59 -07:00
pid.c pidfd: prevent a kernel-doc warning 2023-09-19 13:21:33 -07:00
profile.c
ptrace.c ptrace: Provide set/get interface for syscall user dispatch 2023-04-16 14:23:07 +02:00
range.c
reboot.c kernel/reboot: emergency_restart: Set correct system_state 2023-11-28 17:20:04 +00:00
regset.c
relay.c kernel: relay: remove unnecessary NULL values from relay_open_buf 2023-08-18 10:18:55 -07:00
resource_kunit.c
resource.c dax/kmem: Fix leak of memory-hotplug resources 2023-02-17 14:58:01 -08:00
rseq.c rseq: Extend struct rseq with per-memory-map concurrency ID 2022-12-27 12:52:12 +01:00
scftorture.c scftorture: Pause testing after memory-allocation failure 2023-07-14 15:02:57 -07:00
scs.c scs: add support for dynamic shadow call stacks 2022-11-09 18:06:35 +00:00
seccomp.c seccomp: Add missing kerndoc notations 2023-08-17 12:32:15 -07:00
signal.c signal: print comm and exe name on fatal signals 2023-08-18 10:18:50 -07:00
smp.c smp,csd: Throw an error if a CSD lock is stuck for too long 2023-11-28 17:19:36 +00:00
smpboot.c cpu/hotplug: Remove unused state functions 2023-05-15 13:45:00 +02:00
smpboot.h
softirq.c sched/core: introduce sched_core_idle_cpu() 2023-07-13 15:21:50 +02:00
stackleak.c stackleak: allow to specify arch specific stackleak poison function 2023-04-20 11:36:35 +02:00
stacktrace.c
static_call_inline.c
static_call.c
stop_machine.c
sys_ni.c x86/shstk: Introduce map_shadow_stack syscall 2023-08-02 15:01:51 -07:00
sys.c prctl: Disable prctl(PR_SET_MDWE) on parisc 2023-12-03 07:33:06 +01:00
sysctl-test.c
sysctl.c v6.5-rc1-sysctl-next 2023-06-28 16:05:21 -07:00
task_work.c task_work: add kerneldoc annotation for 'data' argument 2023-09-19 13:21:32 -07:00
taskstats.c
torture.c rcutorture: Fix stuttering races and other issues 2023-11-28 17:20:08 +00:00
tracepoint.c tracepoint: Allow livepatch module add trace event 2023-02-18 14:34:36 -05:00
tsacct.c
ucount.c sysctl: Add size to register_sysctl 2023-08-15 15:26:17 -07:00
uid16.c
uid16.h
umh.c sysctl: fix unused proc_cap_handler() function warning 2023-06-29 15:19:43 -07:00
up.c
user_namespace.c userns: fix a struct's kernel-doc notation 2023-02-02 22:50:04 -08:00
user-return-notifier.c
user.c kernel/user: Allow user_struct::locked_vm to be usable for iommufd 2022-11-30 20:16:49 -04:00
usermode_driver.c
utsname_sysctl.c utsname: simplify one-level sysctl registration for uts_kern_table 2023-04-13 11:49:35 -07:00
utsname.c
vhost_task.c vhost: Fix worker hangs due to missed wake up calls 2023-06-08 15:43:09 -04:00
watch_queue.c kernel: watch_queue: copy user-array safely 2023-11-28 17:19:40 +00:00
watchdog_buddy.c watchdog/hardlockup: move SMP barriers from common code to buddy code 2023-06-19 16:25:28 -07:00
watchdog_perf.c watchdog/perf: add a weak function for an arch to detect if perf can use NMIs 2023-06-09 17:44:21 -07:00
watchdog.c watchdog: move softlockup_panic back to early_param 2023-11-28 17:19:57 +00:00
workqueue_internal.h workqueue: Drop the special locking rule for worker->flags and worker_pool->flags 2023-08-07 15:57:22 -10:00
workqueue.c workqueue: Make sure that wq_unbound_cpumask is never empty 2023-12-13 18:45:24 +01:00