Currently, rcu_torture_writer() checks only for rcu_gp_is_expedited()
when deciding whether or not to do dynamic control of RCU expediting.
This means that if rcupdate.rcu_normal is specified, rcu_torture_writer()
will attempt to dynamically control RCU expediting, but will nonetheless
only test normal RCU grace periods.  This commit therefore adds a check
for !rcu_gp_is_normal(), and prints a message and desists from testing
dynamic control of RCU expediting when doing so is futile.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

This commit consolidates a couple definitions and several calls for
single-shot ftrace-buffer dumping.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

$ make tags
  GEN     tags
ctags: Warning: drivers/acpi/processor_idle.c:64: null expansion of name pattern "\1"
ctags: Warning: drivers/xen/events/events_2l.c:41: null expansion of name pattern "\1"
ctags: Warning: kernel/locking/lockdep.c:151: null expansion of name pattern "\1"
ctags: Warning: kernel/rcu/rcutorture.c:133: null expansion of name pattern "\1"
ctags: Warning: kernel/rcu/rcutorture.c:135: null expansion of name pattern "\1"
ctags: Warning: kernel/workqueue.c:323: null expansion of name pattern "\1"
ctags: Warning: net/ipv4/syncookies.c:53: null expansion of name pattern "\1"
ctags: Warning: net/ipv6/syncookies.c:44: null expansion of name pattern "\1"
ctags: Warning: net/rds/page.c:45: null expansion of name pattern "\1"

Which are all the result of the DEFINE_PER_CPU pattern:

  scripts/tags.sh:200:	'/\<DEFINE_PER_CPU([^,]*, *\([[:alnum:]_]*\)/\1/v/'
  scripts/tags.sh:201:	'/\<DEFINE_PER_CPU_SHARED_ALIGNED([^,]*, *\([[:alnum:]_]*\)/\1/v/'

The below cures them. All except the workqueue one are within reasonable
distance of the 80 char limit. TJ do you have any preference on how to
fix the wq one, or shall we just not care its too long?
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The "Disabled dynamic grace-period expediting" console message is
currently printed unconditionally.  This commit causes it to be
output only when it is impossible to switch between normal and
expedited grace periods, which was the original intent.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Currently, rcu_torture_writer_state is printed as an integer, which slows
debugging.  This commit therefore prints a symbolic name in addition to
the integer.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: More "const", as suggested by Josh Triplett. ]
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

The torturing_tasks() function is used only in kernels built with
CONFIG_PROVE_RCU=y, so the second definition can result in unused-function
compiler warnings.  This commit adds __maybe_unused to suppress these
warnings.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

The rcutorture module has a list of torture types, and specifying a
type not on this list is supposed to cleanly fail the module load.
Unfortunately, the "fail" happens without the "cleanly".  This commit
therefore adds the needed clean-up after an incorrect torture_type.
Reported-by: NDavid Miller <davem@davemloft.net>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: NDavid Miller <davem@davemloft.net>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

This commit moves cond_resched_rcu_qs() into stutter_wait(), saving
a line and also avoiding RCU CPU stall warnings from all torture
loops containing a stutter_wait().
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

We have had the call_rcu_func_t typedef for a quite awhile, but we still
use explicit function pointer types in some places.  These types can
confuse cscope and can be hard to read.  This patch therefore replaces
these types with the call_rcu_func_t typedef.
Signed-off-by: NBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

As we now have rcu_callback_t typedefs as the type of rcu callbacks, we
should use it in call_rcu*() and friends as the type of parameters. This
could save us a few lines of code and make it clear which function
requires an rcu callbacks rather than other callbacks as its argument.

Besides, this can also help cscope to generate a better database for
code reading.
Signed-off-by: NBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

The get_state_synchronize_rcu() and cond_synchronize_rcu() functions
allow polling for grace-period completion, with an actual wait for a
grace period occurring only when cond_synchronize_rcu() is called too
soon after the corresponding get_state_synchronize_rcu().  However,
these functions work only for vanilla RCU.  This commit adds the
get_state_synchronize_sched() and cond_synchronize_sched(), which provide
the same capability for RCU-sched.
Reported-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Although RCU-tasks isn't really designed to support rcu_dereference()
and list manipulation, that is how rcutorture tests it.  Which means
that lockdep-RCU complains about the rcu_dereference_check() invocations
because RCU-tasks doesn't have read-side markers.  This commit therefore
creates a torturing_tasks() to silence the lockdep-RCU complaints from
rcu_dereference_check() when RCU-tasks is being tortured.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

The rcu_torture_cbflood() function correctly checks for flavors of
RCU that lack analogs to call_rcu() and rcu_barrier(), but in that
case it fails to terminate correctly.  In fact, it terminates so
incorrectly that segfaults can result.  This commit therefore causes
rcu_torture_cbflood() to do the proper wait-for-stop procedure.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Specifying a negative rcutorture.shuffle_interval value will cause a
negative value to be used as a sleep time.  This commit therefore
refuses to start shuffling unless the rcutorture.shuffle_interval
value is greater than zero.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Currently, a negative value for rcutorture.nfakewriters= can cause
rcutorture to pass a negative size to the memory allocator, which
is not really a particularly good thing to do.  This commit therefore
adds bounds checking to this parameter, so that values that are less
than or equal to zero disable fake writing.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

A negative value for rcutorture.n_barrier_cbs can pass a negative value
to the memory allocator, so this commit instead causes rcu_barrier()
testing to be disabled in this case.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

The current rcutorture testing does not do any cleanup operations.
This works because the srcu_struct is statically allocated, but it
does represent a memory leak of the associated dynamically allocated
->per_cpu_ref per-CPU variables.  However, rcutorture currently uses
a statically allocated srcu_struct, which cannot legally be passed to
cleanup_srcu_struct().  Therefore, this commit adds a second form
of srcu (called srcud) that dynamically allocates and frees the
associated per-CPU variables.  This commit also adds a ->cleanup()
member to rcu_torture_ops that is invoked at the end of the test,
after ->cb_barriers().  This ->cleanup() pointer is NULL for all
existing tests, and thus only used for scrud.  Finally, the SRCU-P
torture-test configuration selects scrud instead of srcu, with SRCU-N
continuing to use srcu, thereby testing both static and dynamic
srcu_struct structures.
Reported-by: N"Ahmed, Iftekhar" <ahmedi@onid.oregonstate.edu>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

The rcutorture.c file uses several explicit memory barriers that can
easily be converted to smp_store_release() and smp_load_acquire(), which
improves maintainability and also improves performance a bit.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

By default, with rcutorture.nreaders equal to -1, rcutorture provisions
N-1 reader kthreads, where N is the number of CPUs.  This avoids
rcutorture-induced stalls, but also avoids heavier levels of torture.
This commit therefore allows negative values of rcutorture.nreaders
to specify larger numbers of reader kthreads, so that for example
rcutorture.nreaders=-2 provisions N kthreads and rcutorture.nreaders=-5
provisions N+3 kthreads.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Update documentation, as suggested by Josh Triplett. ]

This commit moves from the old ACCESS_ONCE() API to the new READ_ONCE()
and WRITE_ONCE() APIs.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck:  Updated to include kernel/torture.c as suggested by Jason Low. ]

The "if" statement at the beginning of rcu_torture_writer() should
use the same set of variables.  In theory, this does not matter because
the corresponding variables (gp_sync and gp_sync1) have the same value
at this point in the code, but in practice such puzzles should be
removed.  This commit therefore makes the use of variables consistent.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Currently, rcutorture's Reader Batch checks measure from the end of
the previous grace period to the end of the current one.  This commit
tightens up these checks by measuring from the start and end of the same
grace period.  This involves adding rcu_batches_started() and friends
corresponding to the existing rcu_batches_completed() and friends.

We leave SRCU alone for the moment, as it does not yet have a way of
tracking both ends of its grace periods.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Now that the return type of rcu_batches_completed() and friends matches
that of the rcu_torture_ops structure's ->completed field, the wrapper
functions can be deleted.  This commit carries out that deletion, while
also wiring "sched"'s ->completed field to rcu_batches_completed_sched().
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

The counter returned by the various ->completed functions is subject to
overflow, which means that subtracting two such counters might result
in overflow, which invokes undefined behavior in the C standard.  This
commit therefore changes these functions and variables to unsigned to
avoid this undefined behavior.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Commit 38706bc5 (rcutorture: Add callback-flood test) vmalloc()ed
a bunch of RCU callbacks, but failed to free them.  This commit fixes
that oversight.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>

This commit changes rcutorture_runnable to torture_runnable, which is
consistent with the names of the other parameters and is a bit shorter
as well.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

When performing module cleanups by calling torture_cleanup() the
'torture_type' string in nullified However, callers are not necessarily
done, and might still need to reference the variable. This impacts
both rcutorture and locktorture, causing printing things like:

[   94.226618] (null)-torture: Stopping lock_torture_writer task
[   94.226624] (null)-torture: Stopping lock_torture_stats task

Thus delay this operation until the very end of the cleanup process.
The consequence (which shouldn't matter for this kid of program) is,
of course, that we delay the window between rmmod and modprobing,
for instance in module_torture_begin().
Signed-off-by: NDavidlohr Bueso <dbueso@suse.de>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

This commit adds torture tests for RCU-tasks.  It also fixes a bug that
would segfault for an RCU flavor lacking a callback-barrier function.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

RCU-tasks requires the occasional voluntary context switch
from CPU-bound in-kernel tasks.  In some cases, this requires
instrumenting cond_resched().  However, there is some reluctance
to countenance unconditionally instrumenting cond_resched() (see
http://lwn.net/Articles/603252/), so this commit creates a separate
cond_resched_rcu_qs() that may be used in place of cond_resched() in
locations prone to long-duration in-kernel looping.

This commit currently instruments only RCU-tasks.  Future possibilities
include also instrumenting RCU, RCU-bh, and RCU-sched in order to reduce
IPI usage.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Although RCU is designed to handle arbitrary floods of callbacks, this
capability is not routinely tested.   This commit therefore adds a
cbflood capability in which kthreads repeatedly registers large numbers
of callbacks.  One such kthread is created for each four CPUs (rounding
up), and the test may be controlled by several cbflood_* kernel boot
parameters, which control the number of bursts per flood, the number
of callbacks per burst, the time between bursts, and the time between
floods.  The default values are large enough to exercise RCU's emergency
responses to callback flooding.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Miller <davem@davemloft.net>
Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>

User pr_alert/pr_cont for printing the logs from rcutorture module directly
instead of writing it to a buffer and then printing it. This allows us from not
having to allocate such buffers. Also remove a resulting empty function.

I tested this using the parse-torture.sh script as follows:

$ dmesg | grep torture > log.txt
$ bash parse-torture.sh log.txt test
$

There were no warnings which means that parsing went fine.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NPranith Kumar <bobby.prani@gmail.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

This commit fixes the following sparse warning by marking boost_mutex
static:

kernel/rcu/rcutorture.c:185:1: warning: symbol 'boost_mutex' was not declared. Should it be static?
Signed-off-by: NPranith Kumar <bobby.prani@gmail.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

My IBM email addresses haven't worked for years; also map some
old-but-functional forwarding addresses to my canonical address.

Update my GPG key fingerprint; I moved to 4096R a long time ago.

Update description.
Signed-off-by: NJosh Triplett <josh@joshtriplett.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The torture tests are designed to run in isolation, but do not enforce
this isolation.  This commit therefore checks for concurrent torture
tests, and refuses to start new tests while old tests are running.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

There are usually lots of readers and only one writer, so if there has
to be a choice, we would want rcu_torture_writer to win.  This commit
therefore removes the set_user_nice() from rcu_torture_writer().
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

The rcu_torture_reader() function uses an on-stack timer_list structure
which it initializes with setup_timer_on_stack().  However, it fails to
use destroy_timer_on_stack() before exiting, which results in leaking a
tracking object if DEBUG_OBJECTS is enabled.  This commit therefore
invokes destroy_timer_on_stack() to avoid this leakage.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

The original rcu_torture_writer() avoided testing the synchronous
grace-period primitives because they were simply wrappers around
call_rcu() invocations.  The testing of these synchronous primitives
was delegated to the fake writers.  However, there really is no excuse
not to test them, especially in the case of SRCU, where the wrappering
is somewhat more elaborate.  This commit therefore makes the default
rcutorture parameters cause rcu_torture_writer() to include synchronous
grace-period primitives in its testing.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

This commit adds rcutorture testing for get_state_synchronize_rcu()
and cond_synchronize_rcu().
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>