Steven Rostedt (VMware)
a1de406751
ring-buffer: Zero out time extend if it is nested and not absolute ...
commit 097350d1c6e1f5808cae142006f18a0bbc57018d upstream.
Currently the ring buffer makes events that happen in interrupts that preempt
another event have a delta of zero. (Hopefully we can change this soon). But
this is to deal with the races of updating a global counter with lockless
and nesting functions updating deltas.
With the addition of absolute time stamps, the time extend didn't follow
this rule. A time extend can happen if two events happen longer than 2^27
nanoseconds appart, as the delta time field in each event is only 27 bits.
If that happens, then a time extend is injected with 2^59 bits of
nanoseconds to use (18 years). But if the 2^27 nanoseconds happen between
two events, and as it is writing the event, an interrupt triggers, it will
see the 2^27 difference as well and inject a time extend of its own. But a
recent change made the time extend logic not take into account the nesting,
and this can cause two time extend deltas to happen moving the time stamp
much further ahead than the current time. This gets all reset when the ring
buffer moves to the next page, but that can cause time to appear to go
backwards.
This was observed in a trace-cmd recording, and since the data is saved in a
file, with trace-cmd report --debug, it was possible to see that this indeed
did happen!
bash-52501 110d... 81778.908247: sched_switch: bash:52501 [120] S ==> swapper/110:0 [120] [12770284:0x2e8:64]
<idle>-0 110d... 81778.908757: sched_switch: swapper/110:0 [120] R ==> bash:52501 [120] [509947:0x32c:64]
TIME EXTEND: delta:306454770 length:0
bash-52501 110.... 81779.215212: sched_swap_numa: src_pid=52501 src_tgid=52388 src_ngid=52501 src_cpu=110 src_nid=2 dst_pid=52509 dst_tgid=52388 dst_ngid=52501 dst_cpu=49 dst_nid=1 [0:0x378:48]
TIME EXTEND: delta:306458165 length:0
bash-52501 110dNh. 81779.521670: sched_wakeup: migration/110:565 [0] success=1 CPU:110 [0:0x3b4:40]
and at the next page, caused the time to go backwards:
bash-52504 110d... 81779.685411: sched_switch: bash:52504 [120] S ==> swapper/110:0 [120] [8347057:0xfb4:64]
CPU:110 [SUBBUFFER START] [81779379165886:0x1320000]
<idle>-0 110dN.. 81779.379166: sched_wakeup: bash:52504 [120] success=1 CPU:110 [0:0x10:40]
<idle>-0 110d... 81779.379167: sched_switch: swapper/110:0 [120] R ==> bash:52504 [120] [1168:0x3c:64]
Link: https://lkml.kernel.org/r/20200622151815.345d1bf5@oasis.local.home
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: stable@vger.kernel.org
Fixes: dc4e2801d4
2020-06-30 23:17:17 -04:00
cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled
2020-05-02 17:25:53 +02:00
Revert "cgroup: Add memory barriers to plug cgroup_rstat_updated() race window"
2020-06-07 13:17:53 +02:00
kconfig: tinyconfig: remove stale stack protector fixups
2018-06-15 07:15:28 +09:00
kgdb: Prevent infinite recursive entries to the debugger
2020-06-22 09:05:11 +02:00
dma-debug: add a schedule point in debug_dma_dump_mappings()
2020-01-04 19:12:43 +01:00
perf: Add cond_resched() to task_function_call()
2020-06-22 09:05:08 +02:00
kernel/gcov/fs.c: gcov_seq_next() should increase position index
2020-04-29 16:31:12 +02:00
genirq/irqdomain: Check pointer in irq_domain_alloc_irqs_hierarchy()
2020-04-17 10:48:41 +02:00
livepatch: Nullify obj->mod in klp_module_coming()'s error path
2019-10-07 18:57:10 +02:00
locktorture: Print ratio of acquisitions, not failures
2020-04-23 10:30:23 +02:00
PM: hibernate: Freeze kernel threads in software_resume()
2020-05-06 08:13:28 +02:00
printk: fix exclusive_console replaying
2020-02-11 04:33:51 -08:00
rcu: Avoid data-race in rcu_gp_fqs_check_wake()
2020-02-11 04:33:55 -08:00
sched/core: Fix PI boosting between RT and DEADLINE tasks
2020-06-30 23:17:13 -04:00
clocksource: Prevent double add_timer_on() for watchdog_timer
2020-02-11 04:34:18 -08:00
ring-buffer: Zero out time extend if it is nested and not absolute
2020-06-30 23:17:17 -04:00
acct_on(): don't mess with freeze protection
2019-05-31 06:46:05 -07:00
kernel/async.c: revert "async: simplify lowest_in_progress()"
2018-02-06 18:32:44 -08:00
audit: fix a net reference leak in audit_list_rules_send()
2020-06-22 09:05:13 +02:00
audit: fix a net reference leak in audit_list_rules_send()
2020-06-22 09:05:13 +02:00
fsnotify: add fsnotify_add_inode_mark() wrappers
2018-05-18 14:58:22 +02:00
audit: Embed key into chunk
2019-12-13 08:51:11 +01:00
audit_get_nd(): don't unlock parent too early
2019-12-13 08:51:02 +01:00
audit: fix a net reference leak in audit_list_rules_send()
2020-06-22 09:05:13 +02:00
audit: print empty EXECVE args
2019-12-01 09:17:17 +01:00
kbuild: fix kernel/bounds.c 'W=1' warning
2018-11-13 11:08:47 -08:00
LSM: generalize flag passing to security_capable
2020-01-23 08:21:29 +01:00
make 'user_access_begin()' do 'access_ok()'
2020-06-22 09:04:58 +02:00
sched/core: Fix illegal RCU from offline CPUs
2020-06-22 09:05:14 +02:00
kernel/cpu_pm: Fix uninitted local in cpu_pm
2020-06-22 09:05:28 +02:00
kernel/crash_core.c: print timestamp using time64_t
2018-08-22 10:52:47 -07:00
memcg: account security cred as well to kmemcg
2020-01-09 10:19:00 +01:00
delayacct: Use raw_spinlocks
2018-04-27 14:34:51 +02:00
proc: introduce proc_create_single{,_data}
2018-05-16 07:23:35 +02:00
kernel/elfcore.c: include proper prototypes
2019-10-11 18:21:23 +02:00
proc: introduce proc_create_single{,_data}
2018-05-16 07:23:35 +02:00
exit: Move preemption fixup up, move blocking operations down
2020-06-22 09:05:14 +02:00
extable: Make init_kernel_text() global
2018-02-21 16:54:06 +01:00
bpf/error-inject/kprobes: Clear current_kprobe and enable preempt in kprobe
2018-06-21 12:33:19 +02:00
fork,memcg: alloc_thread_stack_node needs to set tsk->stack
2020-01-27 14:50:58 +01:00
PM / reboot: Eliminate race between reboot and suspend
2018-08-06 12:35:20 +02:00
futex: Unbreak futex hashing
2020-03-25 08:06:14 +01:00
kernel: hung_task.c: disable on suspend
2019-04-20 09:16:02 +02:00
memremap: split devm_memremap_pages() and memremap() infrastructure
2018-05-15 23:08:33 -07:00
irq_work: Do not raise an IPI when queueing work on the local CPU
2019-05-31 06:46:19 -07:00
jump_label: move 'asm goto' support test to Kconfig
2019-06-04 08:02:34 +02:00
kallsyms: Don't let kallsyms_lookup_size_offset() fail on retrieving the first symbol
2019-09-21 07:17:02 +02:00
kconfig: include kernel/Kconfig.preempt from init/Kconfig
2018-08-02 08:06:54 +09:00
kernel/kcov.c: mark write_comp_data() as notrace
2019-02-12 19:47:20 +01:00
kexec: add call to LSM hook in original kexec_load syscall
2018-07-16 12:31:57 -07:00
kexec: Allocate decrypted control pages for kdump if SME is enabled
2019-11-24 08:20:29 +01:00
treewide: Use array_size() in vzalloc()
2018-06-12 16:19:22 -07:00
kmod: make request_module() return an error when autoloading is disabled
2020-04-17 10:48:52 +02:00
kretprobe: Prevent triggering kretprobe from within kprobe_flush_task
2020-06-25 15:33:10 +02:00
Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2018-08-13 11:25:07 -07:00
y2038: futex: Move compat implementation into futex.c
2019-12-01 09:17:38 +01:00
mm/memory_hotplug: shrink zones when offlining memory
2020-01-29 16:43:27 +01:00
modsign: log module name in the event of an error
2018-07-02 11:36:17 +02:00
module: avoid setting info->name early in case we can fall back to info->mod->name
2020-02-24 08:34:49 +01:00
modsign: log module name in the event of an error
2018-07-02 11:36:17 +02:00
x86/mm: split vmalloc_sync_all()
2020-03-25 08:06:13 +01:00
padata: purge get_cpu and reorder_via_wq from padata_do_serial
2020-05-27 17:37:36 +02:00
kernel/panic.c: do not append newline to the stack protector panic string
2019-12-01 09:17:10 +01:00
kernel/params.c: downgrade warning for unsafe parameters
2018-04-11 10:28:37 -07:00
Fix failure path in alloc_pid()
2019-01-13 09:51:06 +01:00
signal/pid_namespace: Fix reboot_pid_ns to use send_sig not force_sig
2019-07-26 09:14:01 +02:00
ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()
2020-01-23 08:21:29 +01:00
PM / reboot: Eliminate race between reboot and suspend
2018-08-06 12:35:20 +02:00
kernel/relay.c: handle alloc_percpu returning NULL in relay_open
2020-06-07 13:17:54 +02:00
resource: fix locking in find_next_iomem_res()
2019-09-16 08:22:20 +02:00
rseq: uapi: Declare rseq_cs field as union, update includes
2018-07-10 22:18:52 +02:00
LSM: generalize flag passing to security_capable
2020-01-23 08:21:29 +01:00
signal: Extend exec_id to 64bits
2020-04-17 10:48:47 +02:00
cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM
2019-02-12 19:47:25 +01:00
smpboot: Remove cpumask from the API
2018-07-03 09:20:44 +02:00
nohz: Fix missing tick reprogram when interrupting an inline softirq
2018-08-03 15:52:10 +02:00
Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2018-08-13 11:25:07 -07:00
kernel/sys.c: prctl: fix false positive in validate_prctl_map()
2019-06-15 11:54:01 +02:00
Merge branch 'core-rseq-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2018-06-10 10:17:09 -07:00
kernel: sysctl: make drop_caches write-only
2020-01-04 19:13:17 +01:00
staging: irda: remove remaining remants of irda code removal
2018-04-16 11:26:49 +02:00
taskstats: fix data-race
2020-01-09 10:18:59 +01:00
kprobes: Remove jprobe API implementation
2018-06-21 12:33:05 +02:00
torture: Keep old-school dmesg format
2018-06-25 11:30:10 -07:00
tracepoint: Fix tracepoint array element size mismatch
2018-10-17 15:35:29 -04:00
headers: untangle kmemleak.h from mm.h
2018-04-05 21:36:27 -07:00
fs: add do_fchownat(), ksys_fchown() helpers and ksys_{,l}chown() wrappers
2018-04-02 20:15:59 +02:00
kernel: provide ksys_*() wrappers for syscalls called by kernel/uid16.c
2018-04-02 20:15:30 +02:00
coredump: fix crash when umh is disabled
2020-05-14 07:57:21 +02:00
userns: use irqsave variant of refcount_dec_and_lock()
2018-08-22 10:52:47 -07:00
userns: also map extents in the reverse map to kernel IDs
2018-11-13 11:09:00 -08:00
uts: create "struct uts_namespace" from kmem_cache
2018-04-11 10:28:35 -07:00
sys: don't hold uts_sem while accessing userspace memory
2018-08-11 02:05:53 -05:00
watchdog/softlockup: Enforce that timestamp is valid on boot
2020-02-24 08:34:49 +01:00
watchdog: Mark watchdog touch functions as notrace
2018-08-30 12:56:40 +02:00
workqueue: don't use wq_select_unbound_cpu() for bound works
2020-03-18 07:14:20 +01:00
workqueue: Set worker->desc to workqueue name by default
2018-05-18 08:47:13 -07:00
a1de406751