linux-stable.git/kernel/rcu, branch linux-5.0.y

rcuperf: Fix cleanup path for invalid perf_type strings

2019-05-31T13:45:16+00:00

[ Upstream commit ad092c027713a68a34168942a5ef422e42e039f4 ]

If the specified rcuperf.perf_type is not in the rcu_perf_init()
function's perf_ops[] array, rcuperf prints some console messages and
then invokes rcu_perf_cleanup() to set state so that a future torture
test can run.  However, rcu_perf_cleanup() also attempts to end the
test that didn't actually start, and in doing so relies on the value
of cur_ops, a value that is not particularly relevant in this case.
This can result in confusing output or even follow-on failures due to
attempts to use facilities that have not been properly initialized.

This commit therefore sets the value of cur_ops to NULL in this case and
inserts a check near the beginning of rcu_perf_cleanup(), thus avoiding
relying on an irrelevant cur_ops value.

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

rcutorture: Fix cleanup path for invalid torture_type strings

2019-05-31T13:45:16+00:00

[ Upstream commit b813afae7ab6a5e91b4e16cc567331d9c2ae1f04 ]

If the specified rcutorture.torture_type is not in the rcu_torture_init()
function's torture_ops[] array, rcutorture prints some console messages
and then invokes rcu_torture_cleanup() to set state so that a future
torture test can run.  However, rcu_torture_cleanup() also attempts to
end the test that didn't actually start, and in doing so relies on the
value of cur_ops, a value that is not particularly relevant in this case.
This can result in confusing output or even follow-on failures due to
attempts to use facilities that have not been properly initialized.

This commit therefore sets the value of cur_ops to NULL in this case
and inserts a check near the beginning of rcu_torture_cleanup(),
thus avoiding relying on an irrelevant cur_ops value.

Reported-by: kernel test robot 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Sasha Levin

kprobes: Prohibit probing on RCU debug routine

2019-04-05T20:34:39+00:00

[ Upstream commit a39f15b9644fac3f950f522c39e667c3af25c588 ]

Since kprobe itself depends on RCU, probing on RCU debug
routine can cause recursive breakpoint bugs.

Prohibit probing on RCU debug routines.

int3
 ->do_int3()
   ->ist_enter()
     ->RCU_LOCKDEP_WARN()
       ->debug_lockdep_rcu_enabled() -> int3

Signed-off-by: Masami Hiramatsu 
Cc: Alexander Shishkin 
Cc: Andrea Righi 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Mathieu Desnoyers 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/154998807741.31052.11229157537816341591.stgit@devbox
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

rcu: Do RCU GP kthread self-wakeup from softirq and interrupt

2019-03-23T19:11:38+00:00

commit 1d1f898df6586c5ea9aeaf349f13089c6fa37903 upstream.

The rcu_gp_kthread_wake() function is invoked when it might be necessary
to wake the RCU grace-period kthread.  Because self-wakeups are normally
a useless waste of CPU cycles, if rcu_gp_kthread_wake() is invoked from
this kthread, it naturally refuses to do the wakeup.

Unfortunately, natural though it might be, this heuristic fails when
rcu_gp_kthread_wake() is invoked from an interrupt or softirq handler
that interrupted the grace-period kthread just after the final check of
the wait-event condition but just before the schedule() call.  In this
case, a wakeup is required, even though the call to rcu_gp_kthread_wake()
is within the RCU grace-period kthread's context.  Failing to provide
this wakeup can result in grace periods failing to start, which in turn
results in out-of-memory conditions.

This race window is quite narrow, but it actually did happen during real
testing.  It would of course need to be fixed even if it was strictly
theoretical in nature.

This patch does not Cc stable because it does not apply cleanly to
earlier kernel versions.

Fixes: 48a7639ce80c ("rcu: Make callers awaken grace-period kthread")
Reported-by: "He, Bo" 
Co-developed-by: "Zhang, Jun" 
Co-developed-by: "He, Bo" 
Co-developed-by: "xiao, jin" 
Co-developed-by: Bai, Jie A 
Signed-off: "Zhang, Jun" 
Signed-off: "He, Bo" 
Signed-off: "xiao, jin" 
Signed-off: Bai, Jie A 
Signed-off-by: "Zhang, Jun" 
[ paulmck: Switch from !in_softirq() to "!in_interrupt() &&
  !in_serving_softirq() to avoid redundant wakeups and to also handle the
  interrupt-handler scenario as well as the softirq-handler scenario that
  actually occurred in testing. ]
Signed-off-by: Paul E. McKenney 
Link: https://lkml.kernel.org/r/CD6925E8781EFD4D8E11882D20FC406D52A11F61@SHSMSX104.ccr.corp.intel.com
Signed-off-by: Greg Kroah-Hartman

rcutorture: Don't do busted forward-progress testing

2018-12-01T20:45:42+00:00

The "busted" rcutorture type is an intentionally broken implementation
of RCU.  Doing forward-progress testing on this implementation is not
particularly meaningful on the one hand and can result in fatal abuse
of the memory allocator on the other.  This commit therefore disables
forward-progress testing of the "busted" rcutorture type.

Reported-by: kernel test robot 
Signed-off-by: Paul E. McKenney

rcutorture: Use 100ms buckets for forward-progress callback histograms

2018-12-01T20:45:41+00:00

This commit narrows the scope of each bucket of the forward-progress
callback-invocation histograms from one second to 100 milliseconds, which
aids debugging of forward-progress problems by making shorter-duration
callback-invocation stalls visible.

Signed-off-by: Paul E. McKenney

rcutorture: Recover from OOM during forward-progress tests

2018-12-01T20:45:41+00:00

This commit causes the OOM handler to do rcu_barrier() calls and to
free up forward-progress callbacks in order to recover from OOM events.
The current test is terminated, but subsequent forward-progress tests can
proceed.  This allows a long test to result in multiple forward-progress
failures, greatly reducing the required testing time.

Signed-off-by: Paul E. McKenney

rcutorture: Print forward-progress test age upon failure

2018-12-01T20:45:40+00:00

This commit prints the age of the forward-progress test in jiffies,
in order to allow better interpretation of the callback-invocation
histograms.

Signed-off-by: Paul E. McKenney

rcutorture: Print time since GP end upon forward-progress failure

2018-12-01T20:45:40+00:00

If rcutorture's forward-progress tests fail while a grace period is not
in progress, it is useful to print the time since the last grace period
ended as a way to detect failure to launch a new grace period.  This
commit therefore makes this change.

Signed-off-by: Paul E. McKenney

rcutorture: Print histogram of CB invocation at OOM time

2018-12-01T20:45:39+00:00

One reason why a forward-progress test might fail would be if something
prevented or delayed callback invocation.  This commit therefore adds a
callback-invocation histogram printout when OOM is reported to rcutorture.

Signed-off-by: Paul E. McKenney