The __cpuinit type of throwaway sections might have made sense
some time ago when RAM was more constrained, but now the savings
do not offset the cost and complications. For example, the fix in
commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time")
is a good example of the nasty type of bugs that can be created
with improper use of the various __init prefixes.
After a discussion on LKML[1] it was decided that cpuinit should go
the way of devinit and be phased out. Once all the users are gone,
we can then finally remove the macros themselves from linux/init.h.
This removes all the drivers/rcu uses of the __cpuinit macros
from all C files.
[1] https://lkml.org/lkml/2013/5/20/589
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@freedesktop.org>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
These interfaces never did get used, so this commit removes them,
their rcutorture tests, and documentation referencing them.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The uses of trace_clock_local() are dead code when CONFIG_RCU_TRACE=n,
but some compilers might nevertheless generate code calling this function.
This commit therefore ensures that trace_clock_local() is invoked only
when CONFIG_RCU_TRACE=y.
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
doctorture.2013.01.11a: Changes to rcutorture and to RCU documentation.
fixes.2013.01.26a: Miscellaneous fixes.
tagcb.2013.01.24a: Tag RCU callbacks with grace-period number to
simplify callback advancement.
tiny.2013.01.29b: Enhancements to uniprocessor handling in tiny RCU.
A number of kthreads have been added to rcutorture, but the shuffler
task was not informed of them, and thus did not shuffle them. This
commit therefore adds the requisite shuffling, and, while in the area
fixes up some whitespace issues.
However, the shuffling is intended to keep randomly selected CPUs
idle, which means that the RCU priority boosting kthreads need to
avoid waking up every jiffy. This commit also makes that fix.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Currently, rcutorture traces every read-side access. This can be
problematic because even a two-minute rcutorture run on a two-CPU system
can generate 28,853,363 reads. Normally, only a failing read is of
interest, so this commit traces adjusts rcutorture's tracing to only
trace failing reads. The resulting event tracing records the time
and the ->completed value captured at the beginning of the RCU read-side
critical section, allowing correlation with other event-tracing messages.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
[ paulmck: Add fix to build problem located by Randy Dunlap based on
diagnosis by Steven Rostedt. ]
urgent.2012.10.27a: Fix for RCU user-mode transition (already in -tip).
doc.2012.11.08a: Documentation updates, most notably codifying the
memory-barrier guarantees inherent to grace periods.
fixes.2012.11.13a: Miscellaneous fixes.
srcu.2012.10.27a: Allow statically allocated and initialized srcu_struct
structures (courtesy of Lai Jiangshan).
stall.2012.11.13a: Add more diagnostic information to RCU CPU stall
warnings, also decrease from 60 seconds to 21 seconds.
hotplug.2012.11.08a: Minor updates to CPU hotplug handling.
tracing.2012.11.08a: Improved debugfs tracing, courtesy of Michael Wang.
idle.2012.10.24a: Updates to RCU idle/adaptive-idle handling, including
a boot parameter that maps normal grace periods to expedited.
Resolved conflict in kernel/rcutree.c due to side-by-side change.
Several new rcutorture module parameters have been added, but are not
printed to the console at the beginning and end of tests, which makes
it difficult to reproduce a prior test. This commit therefore adds
these new module parameters to the list printed at the beginning and
the end of the tests.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit causes rcutorture to print the errno if cpu_down() fails
when the rcutorture "verbose" module parameter is specified.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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 <fengguang.wu@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Drop a few characters by switching kernel/rcutorture.c from
"printk(KERN_ALERT" to "pr_alert(".
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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 <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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 <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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 <josh@joshtriplett.org>
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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 <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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 <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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 <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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 <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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 <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Move the raw SRCU interfaces out of the middle of the normal SRCU
interfaces.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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 <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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 <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
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 <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
