linux-toradex.git/kernel/rcutorture.c, branch v3.7

rcu: Prevent initialization race in rcutorture kthreads

2012-09-23T14:42:23+00:00

When you do something like "t = kthread_run(...)", it is possible that
the kthread will start running before the assignment to "t" happens.
If the child kthread expects to find a pointer to its task_struct in "t",
it will then be fatally disappointed.  This commit therefore switches
such cases to kthread_create() followed by wake_up_process(), guaranteeing
that the assignment happens before the child kthread starts running.

Reported-by: Fengguang Wu 
Signed-off-by: Paul E. McKenney

rcu: Switch rcutorture to pr_alert() and friends

2012-09-23T14:42:23+00:00

Drop a few characters by switching kernel/rcutorture.c from
"printk(KERN_ALERT" to "pr_alert(".

Signed-off-by: Paul E. McKenney

rcu: Track CPU-hotplug duration statistics

2012-09-23T14:42:22+00:00

Many rcutorture runs include CPU-hotplug operations in their stress
testing.  This commit accumulates statistics on the durations of these
operations in deference to the recent concern about the overhead and
latency of these operations.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: Update rcutorture defaults

2012-09-23T14:42:22+00:00

A number of new features have been added to rcutorture over the years, but
the defaults have not been updated to include them.  This commit therefore
turns on a couple of them that have proven helpful and trustworthy, namely
periodic progress reports and testing of NO_HZ.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: Fix broken strings in RCU's source code.

2012-07-06T13:01:49+00:00

Although the C language allows you to break strings across lines, doing
this makes it hard for people to find the Linux kernel code corresponding
to a given console message.  This commit therefore fixes broken strings
throughout RCU's source code.

Suggested-by: Josh Triplett 
Suggested-by: Ingo Molnar 
Signed-off-by: Paul E. McKenney

rcu: Fix code-style issues involving "else"

2012-07-06T13:01:48+00:00

The Linux kernel coding style says that single-statement blocks should
omit curly braces unless the other leg of the "if" statement has
multiple statements, in which case the curly braces should be included.
This commit fixes RCU's violations of this rule.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: Make rcutorture fakewriters invoke rcu_barrier()

2012-07-02T19:34:04+00:00

The current rcutorture rcu_barrier() testing never intentionally runs
more than one instance of rcu_barrier() at a given time.  This fails
to test the the shiny new concurrency features of rcu_barrier().  This
commit therefore modifies the rcutorture fakewriter kthread to randomly
invoke rcu_barrier() rather than the usual synchronize_rcu().

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney

rcu: Fix diagnostic-printk typo in rcutorture

2012-07-02T19:34:03+00:00

The rcu_torture_barrier() function has a copy-and-paste typo in the
string passed to rcutorture_shutdown_absorb(), which this commit fixes.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: Fix bug in rcu_barrier() torture test

2012-07-02T19:34:03+00:00

The child threads in the rcu_torture_barrier_cbs() are improperly
synchronized, which can cause the rcu_barrier() tests to hang.  The
failure mode is as follows:

1.	CPU 0 running in rcu_torture_barrier() sets barrier_cbs_count
    	to n_barrier_cbs.

2.	CPU 1 running in rcu_torture_barrier_cbs() wakes up, posts
    	its RCU callback, and atomically decrements barrier_cbs_count.
    	Because barrier_cbs_count is not zero, it does not do the wake_up().

3.	CPU 2 running in rcu_torture_barrier_cbs() wakes up, but
    	finds that barrier_cbs_count is not equal to n_barrier_cbs,
    	and so returns to sleep.

4.	The value of barrier_cbs_count therefore never reaches zero,
    	which causes the test to hang.

This commit therefore uses a phase variable to coordinate the test,
preventing this scenario from occurring.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney

rcu: Test srcu_barrier() from rcutorture test suite

2012-07-02T19:34:03+00:00

SRCU now has a call_srcu() and an srcu_barrier(), but rcutorture does not
test them.  This commit adds the machinery to allow rcutorture's existing
tests for call_rcu() and rcu_barrier() to apply to the SRCU equivalents.

Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett