tracing/osnoise: Fix possible recursive locking for cpus_read_lock()

Lockdep reports this deadlock log:

osnoise: could not start sampling thread
============================================
WARNING

tracing/osnoise: Fix possible recursive locking for cpus_read_lock()

Lockdep reports this deadlock log:

osnoise: could not start sampling thread
============================================
WARNING: possible recursive locking detected
--------------------------------------------
CPU0
----
lock(cpu_hotplug_lock);
lock(cpu_hotplug_lock);

Call Trace:
<TASK>
print_deadlock_bug+0x282/0x3c0
__lock_acquire+0x1610/0x29a0
lock_acquire+0xcb/0x2d0
cpus_read_lock+0x49/0x120
stop_per_cpu_kthreads+0x7/0x60
start_kthread+0x103/0x120
osnoise_hotplug_workfn+0x5e/0x90
process_one_work+0x44f/0xb30
worker_thread+0x33e/0x5e0
kthread+0x206/0x3b0
ret_from_fork+0x31/0x50
ret_from_fork_asm+0x11/0x20
</TASK>

This is the deadlock scenario:
osnoise_hotplug_workfn()
guard(cpus_read_lock)(); // first lock call
start_kthread(cpu)
if (IS_ERR(kthread)) {
stop_per_cpu_kthreads(); {
cpus_read_lock(); // second lock call. Cause the AA deadlock
}
}

It is not necessary to call stop_per_cpu_kthreads() which stops osnoise
kthread for every other CPUs in the system if a failure occurs during
hotplug of a certain CPU.
For start_per_cpu_kthreads(), if the start_kthread() call fails,
this function calls stop_per_cpu_kthreads() to handle the error.
Therefore, similarly, there is no need to call stop_per_cpu_kthreads()
again within start_kthread().
So just remove stop_per_cpu_kthreads() from start_kthread to solve this issue.

Cc: [email protected]
Link: https://lore.kernel.org/[email protected]
Fixes: c8895e271f79 ("trace/osnoise: Support hotplug operations")
Signed-off-by: Ran Xiaokai <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

osnoise: provide quiescent states

To reduce RCU noise for nohz_full configurations, osnoise depends
on cond_resched() providing quiescent states for PREEMPT_RCU=n
configurations. For PREEMPT_RCU=y c

osnoise: provide quiescent states

To reduce RCU noise for nohz_full configurations, osnoise depends
on cond_resched() providing quiescent states for PREEMPT_RCU=n
configurations. For PREEMPT_RCU=y configurations -- where
cond_resched() is a stub -- we do this by directly calling
rcu_momentary_eqs().

With (PREEMPT_LAZY=y, PREEMPT_DYNAMIC=n), however, we have a
configuration with (PREEMPTION=y, PREEMPT_RCU=n) where neither
of the above can help.

Handle that by providing an explicit quiescent state here for all
configurations.

As mentioned above this is not needed for non-stubbed cond_resched(),
but, providing a quiescent state here just pulls in one that a future
cond_resched() would provide, so doesn't cause any extra work for
this configuration.

Cc: Paul E. McKenney <[email protected]>
Cc: Daniel Bristot de Oliveira <[email protected]>
Cc: Steven Rostedt <[email protected]>
Suggested-by: Paul E. McKenney <[email protected]>
Acked-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Ankur Arora <[email protected]>
Reviewed-by: Frederic Weisbecker <[email protected]>
Acked-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

trace/osnoise: Add trace events for samples

Add trace events that fire at osnoise and timerlat sample generation, in
addition to the already existing noise and threshold events.

This allows process

trace/osnoise: Add trace events for samples

Add trace events that fire at osnoise and timerlat sample generation, in
addition to the already existing noise and threshold events.

This allows processing the samples directly in the kernel, either with
ftrace triggers or with BPF.

Cc: John Kacur <[email protected]>
Cc: Luis Goncalves <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Tomas Glozar <[email protected]>
Tested-by: Gabriele Monaco <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/osnoise: Switch to use hrtimer_setup()

hrtimer_setup() takes the callback function pointer as argument and
initializes the timer completely.

Replace hrtimer_init() and the open coded initia

tracing/osnoise: Switch to use hrtimer_setup()

hrtimer_setup() takes the callback function pointer as argument and
initializes the timer completely.

Replace hrtimer_init() and the open coded initialization of
hrtimer::function with the new setup mechanism.

Patch was created by using Coccinelle.

Signed-off-by: Nam Cao <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Steven Rostedt (Google) <[email protected]>
Link: https://lore.kernel.org/all/ff8e6e11df5f928b2b97619ac847b4fa045376a1.1738746821.git.namcao@linutronix.de

show more ...

tracing/osnoise: Fix resetting of tracepoints

If a timerlat tracer is started with the osnoise option OSNOISE_WORKLOAD
disabled, but then that option is enabled and timerlat is removed, the
tracepoi

tracing/osnoise: Fix resetting of tracepoints

If a timerlat tracer is started with the osnoise option OSNOISE_WORKLOAD
disabled, but then that option is enabled and timerlat is removed, the
tracepoints that were enabled on timerlat registration do not get
disabled. If the option is disabled again and timelat is started, then it
triggers a warning in the tracepoint code due to registering the
tracepoint again without ever disabling it.

Do not use the same user space defined options to know to disable the
tracepoints when timerlat is removed. Instead, set a global flag when it
is enabled and use that flag to know to disable the events.

~# echo NO_OSNOISE_WORKLOAD > /sys/kernel/tracing/osnoise/options
~# echo timerlat > /sys/kernel/tracing/current_tracer
~# echo OSNOISE_WORKLOAD > /sys/kernel/tracing/osnoise/options
~# echo nop > /sys/kernel/tracing/current_tracer
~# echo NO_OSNOISE_WORKLOAD > /sys/kernel/tracing/osnoise/options
~# echo timerlat > /sys/kernel/tracing/current_tracer

Triggers:

------------[ cut here ]------------
WARNING: CPU: 6 PID: 1337 at kernel/tracepoint.c:294 tracepoint_add_func+0x3b6/0x3f0
Modules linked in:
CPU: 6 UID: 0 PID: 1337 Comm: rtla Not tainted 6.13.0-rc4-test-00018-ga867c441128e-dirty #73
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:tracepoint_add_func+0x3b6/0x3f0
Code: 48 8b 53 28 48 8b 73 20 4c 89 04 24 e8 23 59 11 00 4c 8b 04 24 e9 36 fe ff ff 0f 0b b8 ea ff ff ff 45 84 e4 0f 84 68 fe ff ff <0f> 0b e9 61 fe ff ff 48 8b 7b 18 48 85 ff 0f 84 4f ff ff ff 49 8b
RSP: 0018:ffffb9b003a87ca0 EFLAGS: 00010202
RAX: 00000000ffffffef RBX: ffffffff92f30860 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9bf59e91ccd0 RDI: ffffffff913b6410
RBP: 000000000000000a R08: 00000000000005c7 R09: 0000000000000002
R10: ffffb9b003a87ce0 R11: 0000000000000002 R12: 0000000000000001
R13: ffffb9b003a87ce0 R14: ffffffffffffffef R15: 0000000000000008
FS: 00007fce81209240(0000) GS:ffff9bf6fdd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055e99b728000 CR3: 00000001277c0002 CR4: 0000000000172ef0
Call Trace:
<TASK>
? __warn.cold+0xb7/0x14d
? tracepoint_add_func+0x3b6/0x3f0
? report_bug+0xea/0x170
? handle_bug+0x58/0x90
? exc_invalid_op+0x17/0x70
? asm_exc_invalid_op+0x1a/0x20
? __pfx_trace_sched_migrate_callback+0x10/0x10
? tracepoint_add_func+0x3b6/0x3f0
? __pfx_trace_sched_migrate_callback+0x10/0x10
? __pfx_trace_sched_migrate_callback+0x10/0x10
tracepoint_probe_register+0x78/0xb0
? __pfx_trace_sched_migrate_callback+0x10/0x10
osnoise_workload_start+0x2b5/0x370
timerlat_tracer_init+0x76/0x1b0
tracing_set_tracer+0x244/0x400
tracing_set_trace_write+0xa0/0xe0
vfs_write+0xfc/0x570
? do_sys_openat2+0x9c/0xe0
ksys_write+0x72/0xf0
do_syscall_64+0x79/0x1c0
entry_SYSCALL_64_after_hwframe+0x76/0x7e

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Tomas Glozar <[email protected]>
Cc: Gabriele Monaco <[email protected]>
Cc: Luis Goncalves <[email protected]>
Cc: John Kacur <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: e88ed227f639e ("tracing/timerlat: Add user-space interface")
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing: Switch trace_osnoise.c code over to use guard() and __free()

The osnoise_hotplug_workfn() grabs two mutexes and cpu_read_lock(). It has
various gotos to handle unlocking them. Switch them o

tracing: Switch trace_osnoise.c code over to use guard() and __free()

The osnoise_hotplug_workfn() grabs two mutexes and cpu_read_lock(). It has
various gotos to handle unlocking them. Switch them over to guard() and
let the compiler worry about it.

The osnoise_cpus_read() has a temporary mask_str allocated and there's
some gotos to make sure it gets freed on error paths. Switch that over to
__free() to let the compiler worry about it.

Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing: Remove TRACE_EVENT_FL_FILTERED logic

After commit dcb0b5575d24 ("tracing: Remove TRACE_EVENT_FL_USE_CALL_FILTER
logic"), no one's going to set the TRACE_EVENT_FL_FILTERED or change the
cal

tracing: Remove TRACE_EVENT_FL_FILTERED logic

After commit dcb0b5575d24 ("tracing: Remove TRACE_EVENT_FL_USE_CALL_FILTER
logic"), no one's going to set the TRACE_EVENT_FL_FILTERED or change the
call->filter, so remove related logic.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Zheng Yejian <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/timerlat: Fix a race during cpuhp processing

There is another found exception that the "timerlat/1" thread was
scheduled on CPU0, and lead to timer corruption finally:

```
ODEBUG: init acti

tracing/timerlat: Fix a race during cpuhp processing

There is another found exception that the "timerlat/1" thread was
scheduled on CPU0, and lead to timer corruption finally:

```
ODEBUG: init active (active state 0) object: ffff888237c2e108 object type: hrtimer hint: timerlat_irq+0x0/0x220
WARNING: CPU: 0 PID: 426 at lib/debugobjects.c:518 debug_print_object+0x7d/0xb0
Modules linked in:
CPU: 0 UID: 0 PID: 426 Comm: timerlat/1 Not tainted 6.11.0-rc7+ #45
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:debug_print_object+0x7d/0xb0
...
Call Trace:
<TASK>
? __warn+0x7c/0x110
? debug_print_object+0x7d/0xb0
? report_bug+0xf1/0x1d0
? prb_read_valid+0x17/0x20
? handle_bug+0x3f/0x70
? exc_invalid_op+0x13/0x60
? asm_exc_invalid_op+0x16/0x20
? debug_print_object+0x7d/0xb0
? debug_print_object+0x7d/0xb0
? __pfx_timerlat_irq+0x10/0x10
__debug_object_init+0x110/0x150
hrtimer_init+0x1d/0x60
timerlat_main+0xab/0x2d0
? __pfx_timerlat_main+0x10/0x10
kthread+0xb7/0xe0
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2d/0x40
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
```

After tracing the scheduling event, it was discovered that the migration
of the "timerlat/1" thread was performed during thread creation. Further
analysis confirmed that it is because the CPU online processing for
osnoise is implemented through workers, which is asynchronous with the
offline processing. When the worker was scheduled to create a thread, the
CPU may has already been removed from the cpu_online_mask during the offline
process, resulting in the inability to select the right CPU:

T1 | T2
[CPUHP_ONLINE] | cpu_device_down()
osnoise_hotplug_workfn() |
| cpus_write_lock()
| takedown_cpu(1)
| cpus_write_unlock()
[CPUHP_OFFLINE] |
cpus_read_lock() |
start_kthread(1) |
cpus_read_unlock() |

To fix this, skip online processing if the CPU is already offline.

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: c8895e271f79 ("trace/osnoise: Support hotplug operations")
Signed-off-by: Wei Li <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/timerlat: Drop interface_lock in stop_kthread()

stop_kthread() is the offline callback for "trace/osnoise:online", since
commit 5bfbcd1ee57b ("tracing/timerlat: Add interface_lock around cle

tracing/timerlat: Drop interface_lock in stop_kthread()

stop_kthread() is the offline callback for "trace/osnoise:online", since
commit 5bfbcd1ee57b ("tracing/timerlat: Add interface_lock around clearing
of kthread in stop_kthread()"), the following ABBA deadlock scenario is
introduced:

T1 | T2 [BP] | T3 [AP]
osnoise_hotplug_workfn() | work_for_cpu_fn() | cpuhp_thread_fun()
| _cpu_down() | osnoise_cpu_die()
mutex_lock(&interface_lock) | | stop_kthread()
| cpus_write_lock() | mutex_lock(&interface_lock)
cpus_read_lock() | cpuhp_kick_ap() |

As the interface_lock here in just for protecting the "kthread" field of
the osn_var, use xchg() instead to fix this issue. Also use
for_each_online_cpu() back in stop_per_cpu_kthreads() as it can take
cpu_read_lock() again.

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: 5bfbcd1ee57b ("tracing/timerlat: Add interface_lock around clearing of kthread in stop_kthread()")
Signed-off-by: Wei Li <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/timerlat: Fix duplicated kthread creation due to CPU online/offline

osnoise_hotplug_workfn() is the asynchronous online callback for
"trace/osnoise:online". It may be congested when a CPU go

tracing/timerlat: Fix duplicated kthread creation due to CPU online/offline

osnoise_hotplug_workfn() is the asynchronous online callback for
"trace/osnoise:online". It may be congested when a CPU goes online and
offline repeatedly and is invoked for multiple times after a certain
online.

This will lead to kthread leak and timer corruption. Add a check
in start_kthread() to prevent this situation.

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: c8895e271f79 ("trace/osnoise: Support hotplug operations")
Signed-off-by: Wei Li <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/osnoise: Fix build when timerlat is not enabled

To fix some critical section races, the interface_lock was added to a few
locations. One of those locations was above where the interface_lock

tracing/osnoise: Fix build when timerlat is not enabled

To fix some critical section races, the interface_lock was added to a few
locations. One of those locations was above where the interface_lock was
declared, so the declaration was moved up before that usage.
Unfortunately, where it was placed was inside a CONFIG_TIMERLAT_TRACER
ifdef block. As the interface_lock is used outside that config, this broke
the build when CONFIG_OSNOISE_TRACER was enabled but
CONFIG_TIMERLAT_TRACER was not.

Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: "Helena Anna" <[email protected]>
Cc: "Luis Claudio R. Goncalves" <[email protected]>
Cc: Tomas Glozar <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: e6a53481da29 ("tracing/timerlat: Only clear timer if a kthread exists")
Reported-by: "Bityutskiy, Artem" <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/timerlat: Add interface_lock around clearing of kthread in stop_kthread()

The timerlat interface will get and put the task that is part of the
"kthread" field of the osn_var to keep it aroun

tracing/timerlat: Add interface_lock around clearing of kthread in stop_kthread()

The timerlat interface will get and put the task that is part of the
"kthread" field of the osn_var to keep it around until all references are
released. But here's a race in the "stop_kthread()" code that will call
put_task_struct() on the kthread if it is not a kernel thread. This can
race with the releasing of the references to that task struct and the
put_task_struct() can be called twice when it should have been called just
once.

Take the interface_lock() in stop_kthread() to synchronize this change.
But to do so, the function stop_per_cpu_kthreads() needs to change the
loop from for_each_online_cpu() to for_each_possible_cpu() and remove the
cpu_read_lock(), as the interface_lock can not be taken while the cpu
locks are held. The only side effect of this change is that it may do some
extra work, as the per_cpu variables of the offline CPUs would not be set
anyway, and would simply be skipped in the loop.

Remove unneeded "return;" in stop_kthread().

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Tomas Glozar <[email protected]>
Cc: John Kacur <[email protected]>
Cc: "Luis Claudio R. Goncalves" <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: e88ed227f639e ("tracing/timerlat: Add user-space interface")
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/timerlat: Only clear timer if a kthread exists

The timerlat tracer can use user space threads to check for osnoise and
timer latency. If the program using this is killed via a SIGTERM, the
t

tracing/timerlat: Only clear timer if a kthread exists

The timerlat tracer can use user space threads to check for osnoise and
timer latency. If the program using this is killed via a SIGTERM, the
threads are shutdown one at a time and another tracing instance can start
up resetting the threads before they are fully closed. That causes the
hrtimer assigned to the kthread to be shutdown and freed twice when the
dying thread finally closes the file descriptors, causing a use-after-free
bug.

Only cancel the hrtimer if the associated thread is still around. Also add
the interface_lock around the resetting of the tlat_var->kthread.

Note, this is just a quick fix that can be backported to stable. A real
fix is to have a better synchronization between the shutdown of old
threads and the starting of new ones.

Link: https://lore.kernel.org/all/[email protected]/

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: "Luis Claudio R. Goncalves" <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: e88ed227f639e ("tracing/timerlat: Add user-space interface")
Reported-by: Tomas Glozar <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/osnoise: Use a cpumask to know what threads are kthreads

The start_kthread() and stop_thread() code was not always called with the
interface_lock held. This means that the kthread variable c

tracing/osnoise: Use a cpumask to know what threads are kthreads

The start_kthread() and stop_thread() code was not always called with the
interface_lock held. This means that the kthread variable could be
unexpectedly changed causing the kthread_stop() to be called on it when it
should not have been, leading to:

while true; do
rtla timerlat top -u -q & PID=$!;
sleep 5;
kill -INT $PID;
sleep 0.001;
kill -TERM $PID;
wait $PID;
done

Causing the following OOPS:

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 5 UID: 0 PID: 885 Comm: timerlatu/5 Not tainted 6.11.0-rc4-test-00002-gbc754cc76d1b-dirty #125 a533010b71dab205ad2f507188ce8c82203b0254
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:hrtimer_active+0x58/0x300
Code: 48 c1 ee 03 41 54 48 01 d1 48 01 d6 55 53 48 83 ec 20 80 39 00 0f 85 30 02 00 00 49 8b 6f 30 4c 8d 75 10 4c 89 f0 48 c1 e8 03 <0f> b6 3c 10 4c 89 f0 83 e0 07 83 c0 03 40 38 f8 7c 09 40 84 ff 0f
RSP: 0018:ffff88811d97f940 EFLAGS: 00010202
RAX: 0000000000000002 RBX: ffff88823c6b5b28 RCX: ffffed10478d6b6b
RDX: dffffc0000000000 RSI: ffffed10478d6b6c RDI: ffff88823c6b5b28
RBP: 0000000000000000 R08: ffff88823c6b5b58 R09: ffff88823c6b5b60
R10: ffff88811d97f957 R11: 0000000000000010 R12: 00000000000a801d
R13: ffff88810d8b35d8 R14: 0000000000000010 R15: ffff88823c6b5b28
FS: 0000000000000000(0000) GS:ffff88823c680000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000561858ad7258 CR3: 000000007729e001 CR4: 0000000000170ef0
Call Trace:
<TASK>
? die_addr+0x40/0xa0
? exc_general_protection+0x154/0x230
? asm_exc_general_protection+0x26/0x30
? hrtimer_active+0x58/0x300
? __pfx_mutex_lock+0x10/0x10
? __pfx_locks_remove_file+0x10/0x10
hrtimer_cancel+0x15/0x40
timerlat_fd_release+0x8e/0x1f0
? security_file_release+0x43/0x80
__fput+0x372/0xb10
task_work_run+0x11e/0x1f0
? _raw_spin_lock+0x85/0xe0
? __pfx_task_work_run+0x10/0x10
? poison_slab_object+0x109/0x170
? do_exit+0x7a0/0x24b0
do_exit+0x7bd/0x24b0
? __pfx_migrate_enable+0x10/0x10
? __pfx_do_exit+0x10/0x10
? __pfx_read_tsc+0x10/0x10
? ktime_get+0x64/0x140
? _raw_spin_lock_irq+0x86/0xe0
do_group_exit+0xb0/0x220
get_signal+0x17ba/0x1b50
? vfs_read+0x179/0xa40
? timerlat_fd_read+0x30b/0x9d0
? __pfx_get_signal+0x10/0x10
? __pfx_timerlat_fd_read+0x10/0x10
arch_do_signal_or_restart+0x8c/0x570
? __pfx_arch_do_signal_or_restart+0x10/0x10
? vfs_read+0x179/0xa40
? ksys_read+0xfe/0x1d0
? __pfx_ksys_read+0x10/0x10
syscall_exit_to_user_mode+0xbc/0x130
do_syscall_64+0x74/0x110
? __pfx___rseq_handle_notify_resume+0x10/0x10
? __pfx_ksys_read+0x10/0x10
? fpregs_restore_userregs+0xdb/0x1e0
? fpregs_restore_userregs+0xdb/0x1e0
? syscall_exit_to_user_mode+0x116/0x130
? do_syscall_64+0x74/0x110
? do_syscall_64+0x74/0x110
? do_syscall_64+0x74/0x110
entry_SYSCALL_64_after_hwframe+0x71/0x79
RIP: 0033:0x7ff0070eca9c
Code: Unable to access opcode bytes at 0x7ff0070eca72.
RSP: 002b:00007ff006dff8c0 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: 0000000000000000 RBX: 0000000000000005 RCX: 00007ff0070eca9c
RDX: 0000000000000400 RSI: 00007ff006dff9a0 RDI: 0000000000000003
RBP: 00007ff006dffde0 R08: 0000000000000000 R09: 00007ff000000ba0
R10: 00007ff007004b08 R11: 0000000000000246 R12: 0000000000000003
R13: 00007ff006dff9a0 R14: 0000000000000007 R15: 0000000000000008
</TASK>
Modules linked in: snd_hda_intel snd_intel_dspcfg snd_intel_sdw_acpi snd_hda_codec snd_hwdep snd_hda_core
---[ end trace 0000000000000000 ]---

This is because it would mistakenly call kthread_stop() on a user space
thread making it "exit" before it actually exits.

Since kthreads are created based on global behavior, use a cpumask to know
when kthreads are running and that they need to be shutdown before
proceeding to do new work.

Link: https://lore.kernel.org/all/[email protected]/

This was debugged by using the persistent ring buffer:

Link: https://lore.kernel.org/all/[email protected]/

Note, locking was originally used to fix this, but that proved to cause too
many deadlocks to work around:

https://lore.kernel.org/linux-trace-kernel/[email protected]/

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: "Luis Claudio R. Goncalves" <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: e88ed227f639e ("tracing/timerlat: Add user-space interface")
Reported-by: Tomas Glozar <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

rcu: Rename rcu_momentary_dyntick_idle() into rcu_momentary_eqs()

The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, replace "dyntick_idle" into "eqs" to drop the

rcu: Rename rcu_momentary_dyntick_idle() into rcu_momentary_eqs()

The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, replace "dyntick_idle" into "eqs" to drop the dyntick
reference.

Signed-off-by: Valentin Schneider <[email protected]>
Reviewed-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Neeraj Upadhyay <[email protected]>

show more ...

rtla/osnoise: set the default threshold to 1us

Change the default threshold for osnoise to 1us, so that any noise
equal or above this value is recorded. Let the user set a higher
threshold if necess

rtla/osnoise: set the default threshold to 1us

Change the default threshold for osnoise to 1us, so that any noise
equal or above this value is recorded. Let the user set a higher
threshold if necessary.

Link: https://lore.kernel.org/linux-trace-kernel/[email protected]

Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Suggested-by: Daniel Bristot de Oliveira <[email protected]>
Reviewed-by: Clark Williams <[email protected]>
Signed-off-by: Luis Claudio R. Goncalves <[email protected]>
Acked-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/timerlat: Move hrtimer_init to timerlat_fd open()

Currently, the timerlat's hrtimer is initialized at the first read of
timerlat_fd, and destroyed at close(). It works, but it causes an erro

tracing/timerlat: Move hrtimer_init to timerlat_fd open()

Currently, the timerlat's hrtimer is initialized at the first read of
timerlat_fd, and destroyed at close(). It works, but it causes an error
if the user program open() and close() the file without reading.

Here's an example:

# echo NO_OSNOISE_WORKLOAD > /sys/kernel/debug/tracing/osnoise/options
# echo timerlat > /sys/kernel/debug/tracing/current_tracer

# cat <<EOF > ./timerlat_load.py
# !/usr/bin/env python3

timerlat_fd = open("/sys/kernel/tracing/osnoise/per_cpu/cpu0/timerlat_fd", 'r')
timerlat_fd.close();
EOF

# ./taskset -c 0 ./timerlat_load.py
<BOOM>

BUG: kernel NULL pointer dereference, address: 0000000000000010
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 1 PID: 2673 Comm: python3 Not tainted 6.6.13-200.fc39.x86_64 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-1.fc39 04/01/2014
RIP: 0010:hrtimer_active+0xd/0x50
Code: 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 57 30 <8b> 42 10 a8 01 74 09 f3 90 8b 42 10 a8 01 75 f7 80 7f 38 00 75 1d
RSP: 0018:ffffb031009b7e10 EFLAGS: 00010286
RAX: 000000000002db00 RBX: ffff9118f786db08 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9117a0e64400 RDI: ffff9118f786db08
RBP: ffff9118f786db80 R08: ffff9117a0ddd420 R09: ffff9117804d4f70
R10: 0000000000000000 R11: 0000000000000000 R12: ffff9118f786db08
R13: ffff91178fdd5e20 R14: ffff9117840978c0 R15: 0000000000000000
FS: 00007f2ffbab1740(0000) GS:ffff9118f7840000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000010 CR3: 00000001b402e000 CR4: 0000000000750ee0
PKRU: 55555554
Call Trace:
<TASK>
? __die+0x23/0x70
? page_fault_oops+0x171/0x4e0
? srso_alias_return_thunk+0x5/0x7f
? avc_has_extended_perms+0x237/0x520
? exc_page_fault+0x7f/0x180
? asm_exc_page_fault+0x26/0x30
? hrtimer_active+0xd/0x50
hrtimer_cancel+0x15/0x40
timerlat_fd_release+0x48/0xe0
__fput+0xf5/0x290
__x64_sys_close+0x3d/0x80
do_syscall_64+0x60/0x90
? srso_alias_return_thunk+0x5/0x7f
? __x64_sys_ioctl+0x72/0xd0
? srso_alias_return_thunk+0x5/0x7f
? syscall_exit_to_user_mode+0x2b/0x40
? srso_alias_return_thunk+0x5/0x7f
? do_syscall_64+0x6c/0x90
? srso_alias_return_thunk+0x5/0x7f
? exit_to_user_mode_prepare+0x142/0x1f0
? srso_alias_return_thunk+0x5/0x7f
? syscall_exit_to_user_mode+0x2b/0x40
? srso_alias_return_thunk+0x5/0x7f
? do_syscall_64+0x6c/0x90
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
RIP: 0033:0x7f2ffb321594
Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d d5 cd 0d 00 00 74 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 3c c3 0f 1f 00 55 48 89 e5 48 83 ec 10 89 7d
RSP: 002b:00007ffe8d8eef18 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00007f2ffba4e668 RCX: 00007f2ffb321594
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007ffe8d8eef40 R08: 0000000000000000 R09: 0000000000000000
R10: 55c926e3167eae79 R11: 0000000000000202 R12: 0000000000000003
R13: 00007ffe8d8ef030 R14: 0000000000000000 R15: 00007f2ffba4e668
</TASK>
CR2: 0000000000000010
---[ end trace 0000000000000000 ]---

Move hrtimer_init to timerlat_fd open() to avoid this problem.

Link: https://lore.kernel.org/linux-trace-kernel/7324dd3fc0035658c99b825204a66049389c56e3.1706798888.git.bristot@kernel.org

Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: [email protected]
Fixes: e88ed227f639 ("tracing/timerlat: Add user-space interface")
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/timerlat: Add user-space interface

Going a step further, we propose a way to use any user-space
workload as the task waiting for the timerlat timer. This is done
via a per-CPU file named osn

tracing/timerlat: Add user-space interface

Going a step further, we propose a way to use any user-space
workload as the task waiting for the timerlat timer. This is done
via a per-CPU file named osnoise/cpu$id/timerlat_fd file.

The tracef_fd allows a task to open at a time. When a task reads
the file, the timerlat timer is armed for future osnoise/timerlat_period_us
time. When the timer fires, it prints the IRQ latency and
wakes up the user-space thread waiting in the timerlat_fd.

The thread then starts to run, executes the timerlat measurement, prints
the thread scheduling latency and returns to user-space.

When the thread rereads the timerlat_fd, the tracer will print the
user-ret(urn) latency, which is an additional metric.

This additional metric is also traced by the tracer and can be used, for
example of measuring the context switch overhead from kernel-to-user and
user-to-kernel, or the response time for an arbitrary execution in
user-space.

The tracer supports one thread per CPU, the thread must be pinned to
the CPU, and it cannot migrate while holding the timerlat_fd. The reason
is that the tracer is per CPU (nothing prohibits the tracer from
allowing migrations in the future). The tracer monitors the migration
of the thread and disables the tracer if detected.

The timerlat_fd is only available for opening/reading when timerlat
tracer is enabled, and NO_OSNOISE_WORKLOAD is set.

The simplest way to activate this feature from user-space is:

-------------------------------- %< -----------------------------------
int main(void)
{
char buffer[1024];
int timerlat_fd;
int retval;
long cpu = 0; /* place in CPU 0 */
cpu_set_t set;

CPU_ZERO(&set);
CPU_SET(cpu, &set);

if (sched_setaffinity(gettid(), sizeof(set), &set) == -1)
return 1;

snprintf(buffer, sizeof(buffer),
"/sys/kernel/tracing/osnoise/per_cpu/cpu%ld/timerlat_fd",
cpu);

timerlat_fd = open(buffer, O_RDONLY);
if (timerlat_fd < 0) {
printf("error opening %s: %s\n", buffer, strerror(errno));
exit(1);
}

for (;;) {
retval = read(timerlat_fd, buffer, 1024);
if (retval < 0)
break;
}

close(timerlat_fd);
exit(0);
}
-------------------------------- >% -----------------------------------

When disabling timerlat, if there is a workload holding the timerlat_fd,
the SIGKILL will be sent to the thread.

Link: https://lkml.kernel.org/r/69fe66a863d2792ff4c3a149bf9e32e26468bb3a.1686063934.git.bristot@kernel.org

Cc: Juri Lelli <[email protected]>
Cc: William White <[email protected]>
Cc: Daniel Bristot de Oliveira <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/osnoise: Skip running osnoise if all instances are off

In the case of all tracing instances being off, sleep for the entire
period.

Q: Why not kill all threads so?
A: It is valid and usef

tracing/osnoise: Skip running osnoise if all instances are off

In the case of all tracing instances being off, sleep for the entire
period.

Q: Why not kill all threads so?
A: It is valid and useful to start the threads with tracing off.
For example, rtla disables tracing, starts the tracer, applies the
scheduling setup to the threads, e.g., sched priority and cgroup,
and then begin tracing with all set.

Skipping the period helps to speed up rtla setup and save the
trace after a stop tracing.

Link: https://lkml.kernel.org/r/aa4dd9b7e76fcb63901fe5407e15ec002b318599.1686063934.git.bristot@kernel.org

Cc: Juri Lelli <[email protected]>
Cc: William White <[email protected]>
Cc: Daniel Bristot de Oliveira <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/osnoise: Switch from PF_NO_SETAFFINITY to migrate_disable

Currently, osnoise/timerlat threads run with PF_NO_SETAFFINITY set.
It works well, however, cgroups do not allow PF_NO_SETAFFINITY t

tracing/osnoise: Switch from PF_NO_SETAFFINITY to migrate_disable

Currently, osnoise/timerlat threads run with PF_NO_SETAFFINITY set.
It works well, however, cgroups do not allow PF_NO_SETAFFINITY threads
to be accepted, and this creates a limitation to osnoise/timerlat.

To avoid this limitation, disable migration of the threads as soon
as they start to run, and then clean the PF_NO_SETAFFINITY flag (still)
used during thread creation.

If for some reason a thread migration is requested, e.g., via
sched_settafinity, the tracer thread will notice and exit.

Link: https://lkml.kernel.org/r/8ba8bc9c15b3ea40cf73cf67a9bc061a264609f0.1686063934.git.bristot@kernel.org

Cc: Juri Lelli <[email protected]>
Cc: William White <[email protected]>
Cc: Daniel Bristot de Oliveira <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/timerlat: Always wakeup the timerlat thread

While testing rtla timerlat auto analysis, I reach a condition where
the interface was not receiving tracing data. I was able to manually
reproduc

tracing/timerlat: Always wakeup the timerlat thread

While testing rtla timerlat auto analysis, I reach a condition where
the interface was not receiving tracing data. I was able to manually
reproduce the problem with these steps:

# echo 0 > tracing_on # disable trace
# echo 1 > osnoise/stop_tracing_us # stop trace if timerlat irq > 1 us
# echo timerlat > current_tracer # enable timerlat tracer
# sleep 1 # wait... that is the time when rtla
# apply configs like prio or cgroup
# echo 1 > tracing_on # start tracing
# cat trace
# tracer: timerlat
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / _-=> migrate-disable
# |||| / delay
# ||||| ACTIVATION
# TASK-PID CPU# ||||| TIMESTAMP ID CONTEXT LATENCY
# | | | ||||| | | | |
NOTHING!

Then, trying to enable tracing again with echo 1 > tracing_on resulted
in no change: the trace was still not tracing.

This problem happens because the timerlat IRQ hits the stop tracing
condition while tracing is off, and do not wake up the timerlat thread,
so the timerlat threads are kept sleeping forever, resulting in no
trace, even after re-enabling the tracer.

Avoid this condition by always waking up the threads, even after stopping
tracing, allowing the tracer to return to its normal operating after
a new tracing on.

Link: https://lore.kernel.org/linux-trace-kernel/1ed8f830638b20a39d535d27d908e319a9a3c4e2.1683822622.git.bristot@kernel.org

Cc: Juri Lelli <[email protected]>
Cc: [email protected]
Fixes: a955d7eac177 ("trace: Add timerlat tracer")
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing: Rename kvfree_rcu() to kvfree_rcu_mightsleep()

The kvfree_rcu() macro's single-argument form is deprecated. Therefore
switch to the new kvfree_rcu_mightsleep() variant. The goal is to
avoi

tracing: Rename kvfree_rcu() to kvfree_rcu_mightsleep()

The kvfree_rcu() macro's single-argument form is deprecated. Therefore
switch to the new kvfree_rcu_mightsleep() variant. The goal is to
avoid accidental use of the single-argument forms, which can introduce
functionality bugs in atomic contexts and latency bugs in non-atomic
contexts.

Cc: Steven Rostedt (VMware) <[email protected]>
Acked-by: Daniel Bristot de Oliveira <[email protected]>
Acked-by: Paul E. McKenney <[email protected]>
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Joel Fernandes (Google) <[email protected]>

show more ...

tracing/osnoise: Fix notify new tracing_max_latency

osnoise/timerlat tracers are reporting new max latency on instances
where the tracing is off, creating inconsistencies between the max
reported va

tracing/osnoise: Fix notify new tracing_max_latency

osnoise/timerlat tracers are reporting new max latency on instances
where the tracing is off, creating inconsistencies between the max
reported values in the trace and in the tracing_max_latency. Thus
only report new tracing_max_latency on active tracing instances.

Link: https://lkml.kernel.org/r/ecd109fde4a0c24ab0f00ba1e9a144ac19a91322.1680104184.git.bristot@kernel.org

Cc: [email protected]
Fixes: dae181349f1e ("tracing/osnoise: Support a list of trace_array *tr")
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/timerlat: Notify new max thread latency

timerlat is not reporting a new tracing_max_latency for the thread
latency. The reason is that it is not calling notify_new_max_latency()
function aft

tracing/timerlat: Notify new max thread latency

timerlat is not reporting a new tracing_max_latency for the thread
latency. The reason is that it is not calling notify_new_max_latency()
function after the new thread latency is sampled.

Call notify_new_max_latency() after computing the thread latency.

Link: https://lkml.kernel.org/r/16e18d61d69073d0192ace07bf61e405cca96e9c.1680104184.git.bristot@kernel.org

Cc: [email protected]
Fixes: dae181349f1e ("tracing/osnoise: Support a list of trace_array *tr")
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...

tracing/osnoise: set several trace_osnoise.c variables storage-class-specifier to static

smatch reports several similar warnings
kernel/trace/trace_osnoise.c:220:1: warning:
symbol '__pcpu_scope_p

tracing/osnoise: set several trace_osnoise.c variables storage-class-specifier to static

smatch reports several similar warnings
kernel/trace/trace_osnoise.c:220:1: warning:
symbol '__pcpu_scope_per_cpu_osnoise_var' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:243:1: warning:
symbol '__pcpu_scope_per_cpu_timerlat_var' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:335:14: warning:
symbol 'interface_lock' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:2242:5: warning:
symbol 'timerlat_min_period' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:2243:5: warning:
symbol 'timerlat_max_period' was not declared. Should it be static?

These variables are only used in trace_osnoise.c, so it should be static

Link: https://lore.kernel.org/linux-trace-kernel/[email protected]

Signed-off-by: Tom Rix <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

show more ...