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There is a need for a non-blocking polling interface for RCU grace
periods, so this commit supplies start_poll_synchronize_rcu() and
poll_state_synchronize_rcu() for this purpose. Note that the existing
get_state_synchronize_rcu() may be used if future grace periods are
inevitable (perhaps due to a later call_rcu() invocation). The new
start_poll_synchronize_rcu() is to be used if future grace periods
might not otherwise happen. Finally, poll_state_synchronize_rcu()
provides a lockless check for a grace period having elapsed since
the corresponding call to either of the get_state_synchronize_rcu()
or start_poll_synchronize_rcu().
As with get_state_synchronize_rcu(), the return value from either
get_state_synchronize_rcu() or start_poll_synchronize_rcu() is passed in
to a later call to either poll_state_synchronize_rcu() or the existing
(might_sleep) cond_synchronize_rcu().
[ paulmck: Revert cond_synchronize_rcu() to might_sleep() per Frederic Weisbecker feedback. ]
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Some versions of grep are happy to interpret a nonsensically placed "-"
within a "[]" pattern as a dash, while others give an error message.
This commit therefore places the "-" at the end of the expression where
it was supposed to be in the first place.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Currently, kvm-again.sh updates the duration in the "seconds=" comment
in the qemu-cmd file, but kvm-transform.sh updates the duration in the
actual qemu command arguments. This is an accident waiting to happen.
This commit therefore consolidates these updates into kvm-transform.sh.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The kvm-again.sh script does not copy over the vmlinux files due to
their large size. This means that a gdb run must use the vmlinux file
from the original "res" directory. This commit therefore finds that
directory and prints it out so that the user can copy and pasted the
gdb command just as for the initial run.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Because the TORTURE_TRUST_MAKE environment variable is not recorded,
kvm-again.sh runs can result in the parse-build.sh script emitting
false-positive "BUG: TREE03 no build" messages. These messages are
intended to complain about any lack of compiler invocations when the
--trust-make flag is not given to kvm.sh. However, when this flag is
given to kvm.sh (and thus when TORTURE_TRUST_MAKE=y), lack of compiler
invocations is expected behavior when rebuilding from identical source
code.
This commit therefore makes kvm-test-1-run.sh record the value of the
TORTURE_TRUST_MAKE environment variable as an additional comment in the
qemu-cmd file, and also makes kvm-again.sh reconstitute that variable
from that comment.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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When rerunning an old run using kvm-again.sh, the jitter commands
will re-use the original "res" directory. This works, but is clearly
an accident waiting to happen. And this accident will happen with
remote runs, where the original directory lives on some other system.
This commit therefore updates the qemu-cmd commands to use the new res
directory created for this specific run.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit adds a --duration argument to kvm-again.sh to allow the user
to override the --duration specified for the original kvm.sh run.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit adds a kvm-again.sh script that, given the results directory
of a torture-test run, re-runs that test. This means that the kernels
need not be rebuilt, but it also is a step towards running torture tests
on remote systems.
This commit also adds a kvm-test-1-run-batch.sh script that runs one
batch out of the torture test. The idea is to copy a results directory
tree to remote systems, then use kvm-test-1-run-batch.sh to run batches
on these systems.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit creates a "batches" file in the res/$ds directory, where $ds
is the datestamp. This file contains the batches and the number of CPUs,
for example:
1 TREE03 16
1 SRCU-P 8
2 TREE07 16
2 TREE01 8
3 TREE02 8
3 TREE04 8
3 TREE05 8
4 SRCU-N 4
4 TRACE01 4
4 TRACE02 4
4 RUDE01 2
4 RUDE01.2 2
4 TASKS01 2
4 TASKS03 2
4 SRCU-t 1
4 SRCU-u 1
4 TASKS02 1
4 TINY01 1
5 TINY02 1
5 TREE09 1
The first column is the batch number, the second the scenario number
(possibly suffixed by a repetition number, as in "RUDE01.2"), and the
third is the number of CPUs required by that scenario. The last line
shows the number of CPUs expected by this batch file, which allows
the run to be re-batched if a different number of CPUs is available.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Although it might be unlikely that someone would name a scenario
"TORTURE_SUITE", they are within their rights to do so. This script
therefore renames the "TORTURE_SUITE" file in the top-level date-stamped
directory within "res" to "torture_suite" to avoid this name collision.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit enforces the defacto restriction on scenario names, which is
that they contain neither "/", ".", nor lowercase alphabetic characters.
This restriction avoids collisions between scenario names and the torture
scripting's files and directories.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The convention that scenario names are all uppercase has two exceptions,
SRCU-t and SRCU-u. This commit therefore renames them to SRCU-T and
SRCU-U, respectively, to bring them in line with this convention. This in
turn permits tighter argument checking in the torture-test scripting.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The cpus2use.sh script complains if the mpstat command is not available,
and instead uses all available CPUs. Unfortunately, this complaint
goes to stdout, where it confuses invokers who expect a single number.
This commit removes this error message in order to avoid this confusion.
The tendency of late has been to give rcutorture a full system, so this
should not cause issues.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit records the process IDs of the kvm-test-1-run.sh and
kvm-test-1-run-qemu.sh scripts to ease monitoring of remotely running
instances of these scripts.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Distributed runs of rcutorture will need to start and stop jittering on
the remote hosts, which means that the commands must be communicated to
those hosts. The commit therefore causes kvm.sh to place these commands
in new TORTURE_JITTER_START and TORTURE_JITTER_STOP environment variables
to communicate them to the scripts that will set this up. In addition,
this commit causes kvm-test-1-run.sh to append these commands to each
generated qemu-cmd file, which allows any remotely executing script to
extract the needed commands from this file.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Currently, kvm-test-1-run.sh both builds and runs an rcutorture kernel,
which is inconvenient when it is necessary to re-run an old run or to
carry out a run on a remote system. This commit therefore extracts the
portion of kvm-test-1-run.sh that invoke qemu to actually run rcutorture
and places it in kvm-test-1-run-qemu.sh.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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When re-running old rcutorture builds, if the original run involved
gdb, the re-run also needs to do so. This commit therefore records the
TORTURE_KCONFIG_GDB_ARG environment variable into the qemu-cmd file so
that the re-run can access it.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit creates jitterstart.sh and jitterstop.sh scripts that handle
the starting and stopping of the jitter.sh scripts. These must be sourced
using the bash "." command to allow the generated script to wait on the
backgrounded jitter.sh scripts.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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There is a need for a non-blocking polling interface for RCU grace
periods, so this commit supplies start_poll_synchronize_rcu() and
poll_state_synchronize_rcu() for this purpose. Note that the existing
get_state_synchronize_rcu() may be used if future grace periods are
inevitable (perhaps due to a later call_rcu() invocation). The new
start_poll_synchronize_rcu() is to be used if future grace periods
might not otherwise happen. Finally, poll_state_synchronize_rcu()
provides a lockless check for a grace period having elapsed since
the corresponding call to either of the get_state_synchronize_rcu()
or start_poll_synchronize_rcu().
As with get_state_synchronize_rcu(), the return value from either
get_state_synchronize_rcu() or start_poll_synchronize_rcu() is passed in
to a later call to either poll_state_synchronize_rcu() or the existing
(might_sleep) cond_synchronize_rcu().
[ paulmck: Remove redundant smp_mb() per Frederic Weisbecker feedback. ]
[ Update poll_state_synchronize_rcu() docbook per Frederic Weisbecker feedback. ]
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Those tracing calls don't need to be under ->nocb_lock. This commit
therefore moves them outside of that lock.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit removes a stale comment claiming that the cblist must be
empty before changing the offloading state. This claim was correct back
when the offloaded state was defined exclusively at boot.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Currently, the bypass is flushed at the very last moment in the
deoffloading procedure. However, this approach leads to a larger state
space than would be preferred. This commit therefore disables the
bypass at soon as the deoffloading procedure begins, then flushes it.
This guarantees that the bypass remains empty and thus out of the way
of the deoffloading procedure.
Symmetrically, this commit waits to enable the bypass until the offloading
procedure has completed.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This sequence of events can lead to a failure to requeue a CPU's
->nocb_timer:
1. There are no callbacks queued for any CPU covered by CPU 0-2's
->nocb_gp_kthread. Note that ->nocb_gp_kthread is associated
with CPU 0.
2. CPU 1 enqueues its first callback with interrupts disabled, and
thus must defer awakening its ->nocb_gp_kthread. It therefore
queues its rcu_data structure's ->nocb_timer. At this point,
CPU 1's rdp->nocb_defer_wakeup is RCU_NOCB_WAKE.
3. CPU 2, which shares the same ->nocb_gp_kthread, also enqueues a
callback, but with interrupts enabled, allowing it to directly
awaken the ->nocb_gp_kthread.
4. The newly awakened ->nocb_gp_kthread associates both CPU 1's
and CPU 2's callbacks with a future grace period and arranges
for that grace period to be started.
5. This ->nocb_gp_kthread goes to sleep waiting for the end of this
future grace period.
6. This grace period elapses before the CPU 1's timer fires.
This is normally improbably given that the timer is set for only
one jiffy, but timers can be delayed. Besides, it is possible
that kernel was built with CONFIG_RCU_STRICT_GRACE_PERIOD=y.
7. The grace period ends, so rcu_gp_kthread awakens the
->nocb_gp_kthread, which in turn awakens both CPU 1's and
CPU 2's ->nocb_cb_kthread. Then ->nocb_gb_kthread sleeps
waiting for more newly queued callbacks.
8. CPU 1's ->nocb_cb_kthread invokes its callback, then sleeps
waiting for more invocable callbacks.
9. Note that neither kthread updated any ->nocb_timer state,
so CPU 1's ->nocb_defer_wakeup is still set to RCU_NOCB_WAKE.
10. CPU 1 enqueues its second callback, this time with interrupts
enabled so it can wake directly ->nocb_gp_kthread.
It does so with calling wake_nocb_gp() which also cancels the
pending timer that got queued in step 2. But that doesn't reset
CPU 1's ->nocb_defer_wakeup which is still set to RCU_NOCB_WAKE.
So CPU 1's ->nocb_defer_wakeup and its ->nocb_timer are now
desynchronized.
11. ->nocb_gp_kthread associates the callback queued in 10 with a new
grace period, arranges for that grace period to start and sleeps
waiting for it to complete.
12. The grace period ends, rcu_gp_kthread awakens ->nocb_gp_kthread,
which in turn wakes up CPU 1's ->nocb_cb_kthread which then
invokes the callback queued in 10.
13. CPU 1 enqueues its third callback, this time with interrupts
disabled so it must queue a timer for a deferred wakeup. However
the value of its ->nocb_defer_wakeup is RCU_NOCB_WAKE which
incorrectly indicates that a timer is already queued. Instead,
CPU 1's ->nocb_timer was cancelled in 10. CPU 1 therefore fails
to queue the ->nocb_timer.
14. CPU 1 has its pending callback and it may go unnoticed until
some other CPU ever wakes up ->nocb_gp_kthread or CPU 1 ever
calls an explicit deferred wakeup, for example, during idle entry.
This commit fixes this bug by resetting rdp->nocb_defer_wakeup everytime
we delete the ->nocb_timer.
It is quite possible that there is a similar scenario involving
->nocb_bypass_timer and ->nocb_defer_wakeup. However, despite some
effort from several people, a failure scenario has not yet been located.
However, that by no means guarantees that no such scenario exists.
Finding a failure scenario is left as an exercise for the reader, and the
"Fixes:" tag below relates to ->nocb_bypass_timer instead of ->nocb_timer.
Fixes: d1b222c6be1f (rcu/nocb: Add bypass callback queueing)
Cc: <stable@vger.kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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RCU triggerse the following sparse warning:
kernel/rcu/tree_plugin.h:1497:5: warning: symbol
'nocb_nobypass_lim_per_jiffy' was not declared. Should it be static?
This commit therefore makes this variable static.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Reported-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit adds a trace event which allows tracing the beginnings of RCU
CPU stall warnings on systems where sysctl_panic_on_rcu_stall is disabled.
The first parameter is the name of RCU flavor like other trace events.
The second parameter indicates whether this is a stall of an expedited
grace period, a self-detected stall of a normal grace period, or a stall
of a normal grace period detected by some CPU other than the one that
is stalled.
RCU CPU stall warnings are often caused by external-to-RCU issues,
for example, in interrupt handling or task scheduling. Therefore,
this event uses TRACE_EVENT, not TRACE_EVENT_RCU, to avoid requiring
those interested in tracing RCU CPU stalls to rebuild their kernels
with CONFIG_RCU_TRACE=y.
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Sangmoon Kim <sangmoon.kim@samsung.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Because preemptible RCU's __rcu_read_unlock() is an external function,
the rough equivalent of an implicit barrier() is inserted by the compiler.
Except that there is a direct call to __rcu_read_unlock() in that same
file, and compilers are getting to the point where they might choose to
inline the fastpath of the __rcu_read_unlock() function.
This commit therefore adds an explicit barrier() to the very beginning
of __rcu_read_unlock().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit replaces "Steve" with the his real name, which is "Stephen".
Reported-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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If there is heavy softirq activity, the softirq system will attempt
to awaken ksoftirqd and will stop the traditional back-of-interrupt
softirq processing. This is all well and good, but only if the
ksoftirqd kthreads already exist, which is not the case during early
boot, in which case the system hangs.
One reproducer is as follows:
tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 2 --configs "TREE03" --kconfig "CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y CONFIG_NO_HZ_IDLE=y CONFIG_HZ_PERIODIC=n" --bootargs "threadirqs=1" --trust-make
This commit therefore adds a couple of existence checks for ksoftirqd
and forces back-of-interrupt softirq processing when ksoftirqd does not
yet exist. With this change, the above test passes.
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: Uladzislau Rezki <urezki@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
[ paulmck: Remove unneeded check per Sebastian Siewior feedback. ]
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Remote rcutorture testing requires that jitter.sh continue to be
invoked from the generated script for local runs, but that it instead
be invoked on the remote system for distributed runs. This argues
for common jitterstart and jitterstop scripts. But it would be good
for jitterstart and jitterstop to control the name and location of the
"jittering" file, while continuing to have the duration controlled by
the caller of these new scripts.
This commit therefore reverses the order of the jittering and duration
parameters for jitter.sh, so that the jittering parameter precedes the
duration parameter.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Now that there is a reliable way to convince the jitter.sh scripts to
stop, the jitter_pids file is not needed, nor is the code that kills all
the PIDs contained in this file. This commit therefore eliminates this
file and the code using it.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Currently, jitter.sh execution is controlled by a time limit and by the
"kill" command. The former allowed jitter.sh to run uselessly past
the end of a set of runs that panicked during boot, and the latter is
vulnerable to PID reuse. This commit therefore introduces a "jittering"
file in the date-stamp directory within "res" that must be present for
the jitter.sh scripts to continue executing. The time limit is still
in place in order to avoid disturbing runs featuring large trace dumps,
but the removal of the "jittering" file handles the panic-during-boot
scenario without relying on PIDs.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Currently, the script generated by kvm.sh does a "wait" to wait on both
the current batch's guest OSes and any jitter.sh scripts. This works,
but makes it hard to abstract the jittering so that common code can be
used for both local and distributed runs. This commit therefore uses
"build.run" files in scenario directories, and these files are removed
after the corresponding scenario's guest OS has completed.
Note that --build-only runs do not create build.run files because they
also do not create guest OSes and do not run any jitter.sh scripts.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Currently the bN.ready and bN.wait files are placed in the
rcutorture directory, which really is not at all a good place
for run-specific files. This commit therefore renames these
files to build.ready and build.wait and then moves them into the
scenario directories within the "res" directory, for example, into
tools/testing/selftests/rcutorture/res/2021.02.10-15.08.23/TINY01.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Given large numbers of threads, the quantity of torture-test output is
sufficient to sometimes result in RCU CPU stall warnings. The probability
of these stall warnings was greatly reduced by batching the output,
but the warnings were not eliminated. However, the actual test only
depends on console output that is printed even when refscale.verbose=0.
This commit therefore causes this test to run with refscale.verbose=0.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Given large numbers of threads, the quantity of torture-test output is
sufficient to sometimes result in RCU CPU stall warnings. The probability
of these stall warnings was greatly reduced by batching the output,
but the warnings were not eliminated. However, the actual test only
depends on console output that is printed even when rcuscale.verbose=0.
This commit therefore causes this test to run with rcuscale.verbose=0.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The testid.txt file was intended for occasional in extremis use, but
now that the new "bare-metal" file references it, it might see more use.
This commit therefore labels sections of output and adds spacing to make
it easier to see what needs to be done to make a bare-metal build tree
match an rcutorture build tree.
Of course, you can avoid this whole issue by building your bare-metal
kernel in the same directory in which you ran rcutorture, but that might
not always be an option.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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In some environments, the torture-testing use of virtualization is
inconvenient. In such cases, the modprobe and rmmod commands may be used
to do torture testing, but significant setup is required to build, boot,
and modprobe a kernel so as to match a given torture-test scenario.
This commit therefore creates a "bare-metal" file in each results
directory containing steps to run the corresponding scenario using the
modprobe command on bare metal. For example, the contents of this file
after using kvm.sh to build an rcutorture TREE01 kernel, perhaps with
the --buildonly argument, is as follows:
To run this scenario on bare metal:
1. Set your bare-metal build tree to the state shown in this file:
/home/git/linux-rcu/tools/testing/selftests/rcutorture/res/2021.02.04-17.10.19/testid.txt
2. Update your bare-metal build tree's .config based on this file:
/home/git/linux-rcu/tools/testing/selftests/rcutorture/res/2021.02.04-17.10.19/TREE01/ConfigFragment
3. Make the bare-metal kernel's build system aware of your .config updates:
$ yes "" | make oldconfig
4. Build your bare-metal kernel.
5. Boot your bare-metal kernel with the following parameters:
maxcpus=8 nr_cpus=43 rcutree.gp_preinit_delay=3 rcutree.gp_init_delay=3 rcutree.gp_cleanup_delay=3 rcu_nocbs=0-1,3-7
6. Start the test with the following command:
$ modprobe rcutorture nocbs_nthreads=8 nocbs_toggle=1000 fwd_progress=0 onoff_interval=1000 onoff_holdoff=30 n_barrier_cbs=4 stat_interval=15 shutdown_secs=120 test_no_idle_hz=1 verbose=1
7. After some time, end the test with the following command:
$ rmmod rcutorture
8. Copy your bare-metal kernel's .config file, overwriting this file:
/home/git/linux-rcu/tools/testing/selftests/rcutorture/res/2021.02.04-17.10.19/TREE01/.config
9. Copy the console output from just before the modprobe to just after
the rmmod into this file:
/home/git/linux-rcu/tools/testing/selftests/rcutorture/res/2021.02.04-17.10.19/TREE01/console.log
10. Check for runtime errors using the following command:
$ tools/testing/selftests/rcutorture/bin/kvm-recheck.sh /home/git/linux-rcu/tools/testing/selftests/rcutorture/res/2021.02.04-17.10.19
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Yes, I do recall a time when 512MB of memory was a lot of mass storage,
much less main memory, but the rcuscale kvfree_rcu() testing invoked by
torture.sh can sometimes exceed it on large systems, resulting in OOM.
This commit therefore causes torture.sh to pase the "--memory 1G"
argument to kvm.sh to reserve a full gigabyte for this purpose.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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If the build fails when running multiple instances of a given rcutorture
scenario, for example, using the kvm.sh --configs "8*RUDE01" argument,
the build will be rerun an additional seven times. This is in some sense
correct, but it can waste significant time. This commit therefore checks
for a prior failed build and simply copies over that build's output.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit replaces a hard-coded "rcu_torture_stall" string in a
pr_alert() format with "%s" and __func__.
Signed-off-by: Stephen Zhang <stephenzhangzsd@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit replaces a hard-coded "torture_init_begin" string in
a pr_alert() format with "%s" and __func__.
Signed-off-by: Stephen Zhang <stephenzhangzsd@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit adds a block comment that gives a high-level overview of
how RCU tasks trace grace periods progress. It also adds a note about
how exiting tasks are handled, plus it gives an overview of the memory
ordering.
Reported-by: Peter Zijlstra <peterz@infradead.org>
Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
[ paulmck: Fix commit log per Mathieu Desnoyers feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The command 'find ./kernel/rcu/ | xargs ./scripts/kernel-doc -none'
reported an issue with the kernel-doc of struct rcu_tasks.
This commit rectifies the kernel-doc, such that no issues remain for
./kernel/rcu/.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The current jitter.sh script expects cpumask bits to fit into whatever
the awk interpreter uses for an integer, which clearly does not hold for
even medium-sized systems these days. This means that on a large system,
only the first 32 or 64 CPUs (depending) are subjected to jitter.sh
CPU-time perturbations. This commit therefore computes a given CPU's
cpumask using text manipulation rather than arithmetic shifts.
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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In kernels built with CONFIG_RCU_STRICT_GRACE_PERIOD=y, every grace
period is an expedited grace period. However, rcu_read_unlock_special()
does not treat them that way, instead allowing the deferred quiescent
state to be reported whenever. This commit therefore adds a check of
this Kconfig option that causes rcu_read_unlock_special() to treat all
grace periods as expedited for CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Currently, rcutorture refuses to test RCU priority boosting in
CONFIG_HOTPLUG_CPU=y kernels, which are the only kind normally built on
x86 these days. This commit therefore updates rcutorture's tests of RCU
priority boosting to make them safe for CPU hotplug. However, these tests
will fail unless TIMER_SOFTIRQ runs at realtime priority, which does not
happen in current mainline. This commit therefore also refuses to test
RCU priority boosting except in kernels built with CONFIG_PREEMPT_RT=y.
While in the area, this commt adds some debug output at boost-fail time
that helps diagnose the cause of the failure, for example, failing to
run TIMER_SOFTIRQ at realtime priority.
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Scott Wood <swood@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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TREE03 tests RCU priority boosting, which is a real-time feature.
It would also be good if it tested something closer to what is
actually used by the real-time folks. This commit therefore adds
tree.use_softirq=0 to the TREE03 kernel boot parameters in TREE03.boot.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Historically, a task that has been subjected to RCU priority boosting is
deboosted at rcu_read_unlock() time. However, with the advent of deferred
quiescent states, if the outermost rcu_read_unlock() was invoked with
either bottom halves, interrupts, or preemption disabled, the deboosting
will be delayed for some time. During this time, a low-priority process
might be incorrectly running at a high real-time priority level.
Fortunately, rcu_read_unlock_special() already provides mechanisms for
forcing a minimal deferral of quiescent states, at least for kernels
built with CONFIG_IRQ_WORK=y. These mechanisms are currently used
when expedited grace periods are pending that might be blocked by the
current task. This commit therefore causes those mechanisms to also be
used in cases where the current task has been or might soon be subjected
to RCU priority boosting. Note that this applies to all kernels built
with CONFIG_RCU_BOOST=y, regardless of whether or not they are also
built with CONFIG_PREEMPT_RT=y.
This approach assumes that kernels build for use with aggressive real-time
applications are built with CONFIG_IRQ_WORK=y. It is likely to be far
simpler to enable CONFIG_IRQ_WORK=y than to implement a fast-deboosting
scheme that works correctly in its absence.
While in the area, alphabetize the rcu_preempt_deferred_qs_handler()
function's local variables.
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Scott Wood <swood@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The name nocb_gp_update_state() is unenlightening, so this commit changes
it to nocb_gp_update_state_deoffloading(). This function now does what
its name says, updates state and returns true if the CPU corresponding to
the specified rcu_data structure is in the process of being de-offloaded.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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At the start of a CPU-hotplug operation, the incoming CPU's callback
list can be in a number of states:
1. Disabled and empty. This is the case when the boot CPU has
not invoked call_rcu(), when a non-boot CPU first comes online,
and when a non-offloaded CPU comes back online. In this case,
it is both necessary and permissible to initialize ->cblist.
Because either the CPU is currently running with interrupts
disabled (boot CPU) or is not yet running at all (other CPUs),
it is not necessary to acquire ->nocb_lock.
In this case, initialization is required.
2. Disabled and non-empty. This cannot occur, because early boot
call_rcu() invocations enable the callback list before enqueuing
their callback.
3. Enabled, whether empty or not. In this case, the callback
list has already been initialized. This case occurs when the
boot CPU has executed an early boot call_rcu() and also when
an offloaded CPU comes back online. In both cases, there is
no need to initialize the callback list: In the boot-CPU case,
the CPU has not (yet) gone offline, and in the offloaded case,
the rcuo kthreads are taking care of business.
Because it is not necessary to initialize the callback list,
it is also not necessary to acquire ->nocb_lock.
Therefore, checking if the segcblist is enabled suffices. This commit
therefore initializes the callback list at rcutree_prepare_cpu() time
only if that list is disabled.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Paul E. McKenney
Frederic Weisbecker
Jiapeng Chong
Sangmoon Kim
Stephen Zhang
Lukas Bulwahn