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Steven Rostedt (Google) da0738f416 tracing: Fix blocked reader of snapshot buffer 
commit 39a7dc23a1ed0fe81141792a09449d124c5953bd upstream.

If an application blocks on the snapshot or snapshot_raw files, expecting
to be woken up when a snapshot occurs, it will not happen. Or it may
happen with an unexpected result.

That result is that the application will be reading the main buffer
instead of the snapshot buffer. That is because when the snapshot occurs,
the main and snapshot buffers are swapped. But the reader has a descriptor
still pointing to the buffer that it originally connected to.

This is fine for the main buffer readers, as they may be blocked waiting
for a watermark to be hit, and when a snapshot occurs, the data that the
main readers want is now on the snapshot buffer.

But for waiters of the snapshot buffer, they are waiting for an event to
occur that will trigger the snapshot and they can then consume it quickly
to save the snapshot before the next snapshot occurs. But to do this, they
need to read the new snapshot buffer, not the old one that is now
receiving new data.

Also, it does not make sense to have a watermark "buffer_percent" on the
snapshot buffer, as the snapshot buffer is static and does not receive new
data except all at once.

Link: https://lore.kernel.org/linux-trace-kernel/20231228095149.77f5b45d@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Fixes: debdd57f5145f ("tracing: Make a snapshot feature available from userspace")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-11-18 12:12:03 +01:00
..
bpf bpf: Fix precision tracking for BPF_ALU | BPF_TO_BE | BPF_END 2024-11-18 11:43:21 +01:00
cgroup cgroup: Remove duplicates in cgroup v1 tasks file 2024-11-08 11:25:51 +01:00
configs Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
debug kgdb: Flush console before entering kgdb on panic 2024-11-18 11:43:15 +01:00
dma Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
entry Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
events perf: Fix perf_event_validate_size() lockdep splat 2024-11-18 12:11:57 +01:00
futex futex: Don't include process MM in futex key on no-MMU 2024-11-18 11:42:47 +01:00
gcov Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irq genirq/generic_chip: Make irq_remove_generic_chip() irqdomain aware 2024-11-18 11:43:25 +01:00
kcsan Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
livepatch livepatch: Fix missing newline character in klp_resolve_symbols() 2024-11-18 11:43:05 +01:00
locking lockdep: Fix block chain corruption 2024-11-18 12:10:56 +01:00
power PM: hibernate: Clean up sync_read handling in snapshot_write_next() 2024-11-18 11:43:24 +01:00
printk printk: Don't allow userspace to write to /dev/kmsg 2024-11-17 17:43:00 +01:00
rcu rcu: kmemleak: Ignore kmemleak false positives when RCU-freeing objects 2024-11-18 11:43:24 +01:00
sched Revert "kernel: ems/ego: Allow CPU frequency changes to be amended before they're set" 2024-11-18 07:48:15 +01:00
time Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
trace tracing: Fix blocked reader of snapshot buffer 2024-11-18 12:12:03 +01:00
acct.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
async.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit_fsnotify.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit_tree.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
audit_watch.c audit: don't WARN_ON_ONCE(!current->mm) in audit_exe_compare() 2024-11-18 11:43:21 +01:00
auditfilter.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
auditsc.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
backtracetest.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
bounds.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
capability.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cfi.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
compat.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
configs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
context_tracking.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpu.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpu_pm.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
crash_core.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
crash_dump.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cred.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
delayacct.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
dma.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
exec_domain.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
exit.c security: samsung: defex_lsm: nuke 2024-06-15 16:20:49 -03:00
extable.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
fail_function.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
fork.c security: samsung: defex_lsm: nuke 2024-06-15 16:20:49 -03:00
freezer.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
gen_kheaders.sh Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
groups.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
hung_task.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
iomem.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irq_work.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
jump_label.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kallsyms.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kcmp.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Kconfig.freezer Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Kconfig.hz Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Kconfig.locks Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Kconfig.preempt Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kcov.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec_core.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec_elf.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec_file.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec_internal.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kheaders.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kmod.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kprobes.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ksysfs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kthread.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
latencytop.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Makefile kernel: Use the stock defconfig for /proc/config.gz 2024-06-15 16:20:14 -03:00
module-internal.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
module.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
module_signature.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
module_signing.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
notifier.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
nsproxy.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
padata.c crypto: pcrypt - Fix hungtask for PADATA_RESET 2024-11-18 11:43:13 +01:00
panic.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
params.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
pid.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
pid_namespace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
profile.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ptrace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
range.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
reboot.c kernel/reboot: emergency_restart: Set correct system_state 2024-11-18 11:43:25 +01:00
regset.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
relay.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
resource.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
rseq.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
scftorture.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
scs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
seccomp.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
signal.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
smp.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
smpboot.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
smpboot.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
softirq.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stackleak.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stacktrace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
static_call.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stop_machine.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sys.c f2fs: Add support for reporting a fake kernel version to fsck 2024-11-17 17:43:26 +01:00
sys_ni.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sysctl-test.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sysctl.c drivers: usb: add toggle for disabling newly added USB devices 2024-10-04 20:09:29 -03:00
task_work.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
taskstats.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
test_kprobes.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
torture.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
tracepoint.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
tsacct.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ucount.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
uid16.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
uid16.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
umh.c security: samsung: defex_lsm: nuke 2024-06-15 16:20:49 -03:00
up.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
user-return-notifier.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
user.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
user_namespace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
usermode_driver.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
utsname.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
utsname_sysctl.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
watch_queue.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
watchdog.c watchdog: move softlockup_panic back to early_param 2024-11-18 11:43:21 +01:00
watchdog_hld.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
workqueue.c Revert "workqueue: remove unused cancel_work()" 2024-11-18 12:11:11 +01:00
workqueue_internal.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00