linux-stable.git/kernel/rcutorture.c, branch v3.5.3

rcu: Add rcutorture test for call_srcu()

2012-04-30T17:48:26+00:00

Add srcu_torture_deferred_free() for srcu_ops so as to test the new
call_srcu().  Rename the original srcu_ops to srcu_sync_ops.

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

rcu: Direct algorithmic SRCU implementation

2012-04-30T17:48:19+00:00

The current implementation of synchronize_srcu_expedited() can cause
severe OS jitter due to its use of synchronize_sched(), which in turn
invokes try_stop_cpus(), which causes each CPU to be sent an IPI.
This can result in severe performance degradation for real-time workloads
and especially for short-interation-length HPC workloads.  Furthermore,
because only one instance of try_stop_cpus() can be making forward progress
at a given time, only one instance of synchronize_srcu_expedited() can
make forward progress at a time, even if they are all operating on
distinct srcu_struct structures.

This commit, inspired by an earlier implementation by Peter Zijlstra
(https://lkml.org/lkml/2012/1/31/211) and by further offline discussions,
takes a strictly algorithmic bits-in-memory approach.  This has the
disadvantage of requiring one explicit memory-barrier instruction in
each of srcu_read_lock() and srcu_read_unlock(), but on the other hand
completely dispenses with OS jitter and furthermore allows SRCU to be
used freely by CPUs that RCU believes to be idle or offline.

The update-side implementation handles the single read-side memory
barrier by rechecking the per-CPU counters after summing them and
by running through the update-side state machine twice.

This implementation has passed moderate rcutorture testing on both
x86 and Power.  Also updated to use this_cpu_ptr() instead of per_cpu_ptr(),
as suggested by Peter Zijlstra.

Reported-by: Peter Zijlstra 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney 
Acked-by: Peter Zijlstra 
Reviewed-by: Lai Jiangshan

rcu: Introduce rcutorture testing for rcu_barrier()

2012-04-30T17:48:18+00:00

Although rcutorture does invoke rcu_barrier() and friends, it cannot
really be called a torture test given that it invokes them only once
at the end of the test.  This commit therefore introduces heavy-duty
rcutorture testing for rcu_barrier(), which may be carried out
concurrently with normal rcutorture testing.

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

rcu: Fixes to rcutorture error handling and cleanup

2012-04-25T03:55:39+00:00

The rcutorture initialization code ignored the error returns from
rcu_torture_onoff_init() and rcu_torture_stall_init().  The rcutorture
cleanup code failed to NULL out a number of pointers.  These bugs will
normally have no effect, but this commit fixes them nevertheless.

Signed-off-by: Paul E. McKenney

PTR_ERR should be called before its argument is cleared.

2012-02-21T17:06:10+00:00

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// 
@@
expression e,e1;
constant c;
@@

*e = c
... when != e = e1
    when != &e
    when != true IS_ERR(e)
*PTR_ERR(e)
// 

Signed-off-by: Julia Lawall 
Reported-by: Josh Triplett 
Signed-off-by: Paul E. McKenney

rcu: Trace only after NULL-pointer check

2012-02-21T17:06:09+00:00

Fix a bonehead error introduced when adding event tracing to rcutorture.
Move the traces to follow the NULL-pointer checks.

Signed-off-by: Paul E. McKenney

rcu: Add CPU-stall capability to rcutorture

2012-02-21T17:03:52+00:00

Add module parameters to rcutorture that induce a CPU stall.
The stall_cpu parameter specifies how long to stall in seconds,
defaulting to zero, which indicates no stalling is to be undertaken.
The stall_cpu_holdoff parameter specifies how many seconds after
insmod (or boot, if rcutorture is built into the kernel) that this
stall is to start.  The default value for stall_cpu_holdoff is ten
seconds.

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

rcutorture: Permit holding off CPU-hotplug operations during boot

2012-02-21T17:03:50+00:00

When rcutorture is started automatically at boot time, it might well
also start CPU-hotplug operations at that time, which might not be
desirable.  This commit therefore adds an rcutorture parameter that
allows CPU-hotplug operations to be held off for the specified number
of seconds after the start of boot.

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

rcu: Make rcutorture flag online/offline failures

2012-02-21T17:03:35+00:00

Make rcutorture check for CPU-hotplug failures and complain if there
were any.

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

rcu: Add missing __cpuinit annotation in rcutorture code

2012-01-16T17:44:05+00:00

"rcu: Add rcutorture CPU-hotplug capability" adds cpu hotplug operations
to the rcutorture code but produces a false positive warning about section
mismatches:

WARNING: vmlinux.o(.text+0x1e420c): Section mismatch in reference from the
	 function rcu_torture_onoff() to the function .cpuinit.text:cpu_up()
	 The function rcu_torture_onoff() references
	 the function __cpuinit cpu_up().
	 This is often because rcu_torture_onoff lacks a __cpuinit
	 annotation or the annotation of cpu_up is wrong.

This commit therefore adds a __cpuinit annotation so the warning goes away.

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