linux.git/kernel/torture.c, branch v6.6.132

rcutorture: Fix stuttering races and other issues

2023-11-28T17:20:08+00:00

[ Upstream commit cca42bd8eb1b54a4c9bbf48c79d120e66619a3e4 ]

The stuttering code isn't functioning as expected. Ideally, it should
pause the torture threads for a designated period before resuming. Yet,
it fails to halt the test for the correct duration. Additionally, a race
condition exists, potentially causing the stuttering code to pause for
an extended period if the 'spt' variable is non-zero due to the stutter
orchestration thread's inadequate CPU time.

Moreover, over-stuttering can hinder RCU's progress on TREE07 kernels.
This happens as the stuttering code may run within a softirq due to RCU
callbacks. Consequently, ksoftirqd keeps a CPU busy for several seconds,
thus obstructing RCU's progress. This situation triggers a warning
message in the logs:

[ 2169.481783] rcu_torture_writer: rtort_pipe_count: 9

This warning suggests that an RCU torture object, although invisible to
RCU readers, couldn't make it past the pipe array and be freed -- a
strong indication that there weren't enough grace periods during the
stutter interval.

To address these issues, this patch sets the "stutter end" time to an
absolute point in the future set by the main stutter thread. This is
then used for waiting in stutter_wait(). While the stutter thread still
defines this absolute time, the waiters' waiting logic doesn't rely on
the stutter thread receiving sufficient CPU time to halt the stuttering
as the halting is now self-controlled.

Cc: stable@vger.kernel.org
Signed-off-by: Joel Fernandes (Google) 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Sasha Levin

torture: Make torture_hrtimeout_ns() take an hrtimer mode parameter

2023-11-28T17:20:08+00:00

[ Upstream commit a741deac787f0d2d7068638c067db20af9e63752 ]

The current torture-test sleeps are waiting for a duration, but there
are situations where it is better to wait for an absolute time, for
example, when ending a stutter interval.  This commit therefore adds
an hrtimer mode parameter to torture_hrtimeout_ns().  Why not also the
other torture_hrtimeout_*() functions?  The theory is that most absolute
times will be in nanoseconds, especially not (say) jiffies.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Frederic Weisbecker 
Stable-dep-of: cca42bd8eb1b ("rcutorture: Fix stuttering races and other issues")
Signed-off-by: Sasha Levin

torture: Stop right-shifting torture_random() return values

2023-08-14T22:01:08+00:00

Now that torture_random() uses swahw32(), its callers no longer see
not-so-random low-order bits, as these are now swapped up into the upper
16 bits of the torture_random() function's return value.  This commit
therefore removes the right-shifting of torture_random() return values.

Signed-off-by: Paul E. McKenney

torture: Move stutter_wait() timeouts to hrtimers

2023-08-14T22:01:08+00:00

In order to gain better race coverage, move the test start/stop
waits in stutter_wait() to torture_hrtimeout_jiffies().

Signed-off-by: Paul E. McKenney

torture: Move torture_shuffle() timeouts to hrtimers

2023-08-14T22:01:08+00:00

In order to gain better race coverage, move the CPU-migration timed
waits in torture_shuffle() to torture_hrtimeout_jiffies().

Signed-off-by: Paul E. McKenney

torture: Move torture_onoff() timeouts to hrtimers

2023-08-14T22:01:08+00:00

In order to gain better race coverage, move the CPU-hotplug-related
timed waits in torture_onoff() to torture_hrtimeout_jiffies().

Signed-off-by: Paul E. McKenney

torture: Make torture_hrtimeout_*() use TASK_IDLE

2023-08-14T22:01:07+00:00

Given that it is expected that more code will use torture_hrtimeout_*(),
including for longer timeouts, make it use TASK_IDLE instead of
TASK_UNINTERRUPTIBLE.

Signed-off-by: Paul E. McKenney

torture: Add lock_torture writer_fifo module parameter

2023-08-14T22:01:07+00:00

This commit adds a module parameter that causes the locktorture writer
to run at real-time priority.

To use it:
insmod /lib/modules/torture.ko random_shuffle=1
insmod /lib/modules/locktorture.ko torture_type=mutex_lock rt_boost=1 rt_boost_factor=50 nested_locks=3 writer_fifo=1
													^^^^^^^^^^^^^

A predecessor to this patch has been helpful to uncover issues with the
proxy-execution series.

[ paulmck: Remove locktorture-specific code from kernel/torture.c. ]

Cc: "Paul E. McKenney" 
Cc: Josh Triplett 
Cc: Joel Fernandes 
Cc: Juri Lelli 
Cc: Valentin Schneider 
Cc: kernel-team@android.com
Signed-off-by: Dietmar Eggemann 
[jstultz: Include header change to build, reword commit message]
Signed-off-by: John Stultz 
Acked-by: Davidlohr Bueso 
Signed-off-by: Paul E. McKenney

torture: Add a kthread-creation callback to _torture_create_kthread()

2023-08-14T22:00:37+00:00

This commit adds a kthread-creation callback to the
_torture_create_kthread() function, which allows callers of a new
torture_create_kthread_cb() macro to specify a function to be invoked
after the kthread is created but before it is awakened for the first time.

Signed-off-by: Paul E. McKenney 
Cc: Dietmar Eggemann 
Cc: Josh Triplett 
Cc: Juri Lelli 
Cc: Valentin Schneider 
Cc: Dietmar Eggemann 
Cc: kernel-team@android.com
Reviewed-by: Joel Fernandes (Google) 
Acked-by: John Stultz

torture: Support randomized shuffling for proxy exec testing

2023-07-14T22:04:09+00:00

Currently shuffling sets the same cpu affinities for all tasks,
which makes us less likely to hit paths involving migrating
blocked tasks onto a cpu where they can't run.

This patch adds an element of randomness to allow affinities of
different writer tasks to diverge.

This has helped uncover issues in testing with Proxy Execution

Cc: "Paul E. McKenney" 
Cc: Josh Triplett 
Cc: Joel Fernandes 
Cc: Juri Lelli 
Cc: Valentin Schneider 
Cc: Dietmar Eggemann 
Cc: kernel-team@android.com
Signed-off-by: Connor O'Brien 
Signed-off-by: John Stultz 
Acked-by: Davidlohr Bueso 
Signed-off-by: Paul E. McKenney