- 16 Sep, 2014 15 commits
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Paul E. McKenney authored
Merge branches 'doc.2014.09.07a', 'fixes.2014.09.10a', 'nocb-nohz.2014.09.16b' and 'torture.2014.09.07a' into HEAD doc.2014.09.07a: Documentation updates. fixes.2014.09.10a: Miscellaneous fixes. nocb-nohz.2014.09.16b: No-CBs CPUs and NO_HZ_FULL updates. torture.2014.09.07a: Torture-test updates.
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Paul E. McKenney authored
The NOCB follower wakeup ordering depends on the store to the tail pointer happening before the wakeup. However, because atomic_long_add() does not return a value, it does not provide ordering guarantees, and the locking in wake_up() only guarantees that the store will happen before the unlock, which might be too late. Even though this is only a theoretical issue, this commit adds a smp_mb__after_atomic() after the final atomic_long_add() to provide the needed ordering guarantee. Reported-by:
Amit Shah <amit.shah@redhat.com> Signed-off-by:
Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by:
Paul Gortmaker <paul.gortmaker@windriver.com>
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Paul E. McKenney authored
If an RCU callback is queued on a no-CBs CPU from idle code with irqs disabled, and if that CPU stays idle forever after, the callback will never be invoked. This commit therefore adds a check for this situation in ____call_rcu_nocb(), invoking the RCU core solely for the purpose of the ensuing return-to-idle transition. (If the CPU doesn't return to idle, the next scheduling-clock interrupt will fix things up.) Reported-by:
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Paul E. McKenney authored
The NOCB leader wakeup ordering depends on the store to the header happening before the check for the leader already being awake. However, because atomic_long_add() does not return a value, it does not provide ordering guarantees, the incorrect comment in wake_nocb_leader() notwithstanding. This commit therefore adds a smp_mb__after_atomic() after the final atomic_long_add() to provide the needed ordering guarantee. Reported-by:
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Paul E. McKenney authored
If there are no nohz_full= CPUs, then there is currently no reason to track sysidle state. This commit therefore short-circuits this state tracking if !tick_nohz_full_enabled(). Note that these checks will need to be revisited if nohz_full= state can ever be changed at runtime. Signed-off-by:
Frederic Weisbecker <fweisbec@gmail.com> Tested-by:
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Paul E. McKenney authored
Now that we have rcu_state_p, which references rcu_preempt_state for TREE_PREEMPT_RCU and rcu_sched_state for TREE_RCU, we don't need a separate rcu_sysidle_state variable. This commit therefore eliminates rcu_preempt_state in favor of rcu_state_p. Signed-off-by:
Pranith Kumar <bobby.prani@gmail.com> Acked-by:
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Pranith Kumar authored
If we configure a kernel with CONFIG_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_NONE=y and CONFIG_CPUMASK_OFFSTACK=n and do not pass in a rcu_nocb= boot parameter, the cpumask rcu_nocb_mask can be garbage instead of NULL. Hence this commit replaces checks for rcu_nocb_mask == NULL with a check for have_rcu_nocb_mask. Signed-off-by:
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Paul E. McKenney authored
RCU currently uses for_each_possible_cpu() to spawn rcuo kthreads, which can result in more rcuo kthreads than one would expect, for example, derRichard reported 64 CPUs worth of rcuo kthreads on an 8-CPU image. This commit therefore creates rcuo kthreads only for those CPUs that actually come online. This was reported by derRichard on the OFTC IRC network. Reported-by:
Richard Weinberger <richard@nod.at> Signed-off-by:
Josh Triplett <josh@joshtriplett.org> Tested-by:
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Paul E. McKenney authored
Currently, RCU spawns kthreads from several different early_initcall() functions. Although this has served RCU well for quite some time, as more kthreads are added a more deterministic approach is required. This commit therefore causes all of RCU's early-boot kthreads to be spawned from a single early_initcall() function. Signed-off-by:
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Pranith Kumar authored
Return false instead of 0 in rcu_nocb_adopt_orphan_cbs() as this has bool as return type. Signed-off-by:
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Pranith Kumar authored
Return false instead of 0 in __call_rcu_nocb() as this has bool as return type. Signed-off-by:
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Pranith Kumar authored
Return true/false in rcu_nocb_adopt_orphan_cbs() instead of 0/1 as this function has return type of bool. Signed-off-by:
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Pranith Kumar authored
Return true/false instead of 0/1 in __call_rcu_nocb() as this returns a bool type. Signed-off-by:
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Pranith Kumar authored
This commit checks the return value of the zalloc_cpumask_var() used for allocating cpumask for rcu_nocb_mask. Signed-off-by:
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Paul E. McKenney authored
Commit b58cc46c (rcu: Don't offload callbacks unless specifically requested) failed to adjust the callback lists of the CPUs that are known to be no-CBs CPUs only because they are also nohz_full= CPUs. This failure can result in callbacks that are posted during early boot getting stranded on nxtlist for CPUs whose no-CBs property becomes apparent late, and there can also be spurious warnings about offline CPUs posting callbacks. This commit fixes these problems by adding an early-boot rcu_init_nohz() that properly initializes the no-CBs CPUs. Note that kernels built with CONFIG_RCU_NOCB_CPU_ALL=y or with CONFIG_RCU_NOCB_CPU=n do not exhibit this bug. Neither do kernels booted without the nohz_full= boot parameter. Signed-off-by:
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- 07 Sep, 2014 25 commits
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Paul E. McKenney authored
When starting a new torture run while an old one is still running, both qemu processes can be outputting to the same console.out file. This can cause quite a bit of confusion, so this commit checks for this situation, which is normally indicated by nul bytes in the console output. Yes, if your new run uses up an exact number of blocks of the file, this check will be ineffective, but the odds are not bad. Signed-off-by:
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Paul E. McKenney authored
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Paul E. McKenney authored
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:
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Joe Perches authored
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:
Joe Perches <joe@perches.com> Signed-off-by:
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Paul E. McKenney authored
This commit specifies offstack cpumasks in TREE07 in order to catch references to unallocated cpumask_var_t variables. Signed-off-by:
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Paul E. McKenney authored
Setting CONFIG_MAXSMP=y causes cpumasks to be moved offstack, which introduces the possibility of NULL cpumask_var_t pointers. This commit therefore enables CONFIG_MAXSMP=y in TREE01 to increase test coverage. However, because CONFIG_MAXSMP=y implies 8192 CPUs, we need to use the maxcpus= boot parameter to limit the number of CPUs to something reasonable, which in turn requires updating the scripts to handle this. Signed-off-by:
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Paul E. McKenney authored
The current set of tests covers only cases where either all possible CPUs are nohz_full= CPUs or none of them are. Because there have been some recent bug escapes in cases where only some of the CPUs are nohz_full= CPUs, this commit add a configuration where only half of the CPUs are nohz_full= CPUs. Signed-off-by:
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Paul E. McKenney authored
This commit tries to get people into the correct directory before creating the initrd directory. Signed-off-by:
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Pranith Kumar authored
This commit sets the executable bit on test scripts config2frag.sh and kvm.sh. Since #!/bin/bash is set in all the scripts, this commit also drops it from all usage lines because the scripts can now all be invoked directly. Signed-off-by:
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Pranith Kumar authored
Some of the scripts encode a default /bin/sh shell. On systems which use dash as default shell, these scripts fail as they are bash scripts. I encountered this while testing the sprintf() changes on a Debian system where dash is the default shell. This commit changes all such uses to use bash explicitly. Signed-off-by:
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Pranith Kumar authored
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:
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Paul E. McKenney authored
Currently, when RCU awakens from a wait_event_interruptible() that might have awakened prematurely, it does a flush_signals(). This is done on the off-chance that someone figured out how to deliver a signal to a kthread, which is supposed to be impossible. Given that this is supposed to be impossible, this commit changes the flush_signals() calls into WARN_ON(signal_pending()). Reported-by:
Oleg Nesterov <oleg@redhat.com> Signed-off-by:
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Pranith Kumar authored
The rcu_gp_kthread_wake() function checks for three conditions before waking up grace period kthreads: * Is the thread we are trying to wake up the current thread? * Are the gp_flags zero? (all threads wait on non-zero gp_flags condition) * Is there no thread created for this flavour, hence nothing to wake up? If any one of these condition is true, we do not call wake_up(). It was found that there are quite a few avoidable wake ups both during idle time and under stress induced by rcutorture. Idle: Total:66000, unnecessary:66000, case1:61827, case2:66000, case3:0 Total:68000, unnecessary:68000, case1:63696, case2:68000, case3:0 rcutorture: Total:254000, unnecessary:254000, case1:199913, case2:254000, case3:0 Total:256000, unnecessary:256000, case1:201784, case2:256000, case3:0 Here case{1-3} are the cases listed above. We can avoid these wake ups by using rcu_gp_kthread_wake() to conditionally wake up the grace period kthreads. There is a comment about an implied barrier supplied by the wake_up() logic. This barrier is necessary for the awakened thread to see the updated ->gp_flags. This flag is always being updated with the root node lock held. Also, the awakened thread tries to acquire the root node lock before reading ->gp_flags because of which there is proper ordering. Hence this commit tries to avoid calling wake_up() whenever we can by using rcu_gp_kthread_wake() function. Signed-off-by: -
Paul E. McKenney authored
The rcu_idle_enter_common() and rcu_idle_exit_common() functions contain error checks that have to the best of my knowledge have never triggered over the past several years. These are nevertheless valuable when creating new architectures or doing other low-level changes, so the checks should not be deleted. This commit instead places these checks under #ifdef CONFIG_RCU_TRACE so that they are executed only when specifically requested. The savings are significant: Before: text data bss dec hex filename 1749 39 0 1788 6fc /tmp/b/kernel/rcu/tiny.o 632 152 0 784 310 /tmp/b/kernel/rcu/update.o ---- 2572 After: text data bss dec hex filename 1281 37 0 1318 526 /tmp/b/kernel/rcu/tiny.o 632 152 0 784 310 /tmp/b/kernel/rcu/update.o ---- 2102 This amounts to 470 bytes, or 18% of the original. Switched from #ifdef to IS_ENABLED() on Josh Triplett's advice. Signed-off-by:
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Paul E. McKenney authored
Commit 96d3fd0d (rcu: Break call_rcu() deadlock involving scheduler and perf) covered the case where __call_rcu_nocb_enqueue() needs to wake the rcuo kthread due to the queue being initially empty, but did not do anything for the case where the queue was overflowing. This commit therefore also defers wakeup for the overflow case. Signed-off-by:
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Pranith Kumar authored
This commit removes a stale comment in rcu/tree.c which was left out when some code was moved around previously in commit 2036d94a ("rcu: Rework detection of use of RCU by offline CPUs") For reference, the following updated comment exists a few lines below this which means the same: /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ Signed-off-by:
Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by:
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Pranith Kumar authored
This commit updates the references to rcutree.c which is now rcu/tree.c Signed-off-by:
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Ard Biesheuvel authored
Commit f7f7bac9 ("rcu: Have the RCU tracepoints use the tracepoint_string infrastructure") unconditionally populates the __tracepoint_str input section, but this section is not assigned an output section if CONFIG_TRACING is not set. This results in the __tracepoint_str turning up in unexpected places, i.e., after _edata. Signed-off-by:
Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by:
Steven Rostedt <rostedt@goodmis.org> Signed-off-by:
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Oleg Nesterov authored
This commit uninlines rcu_read_lock_held(). According to "size vmlinux" this saves 28549 in .text: - 5541731 3014560 14757888 23314179 + 5513182 3026848 14757888 23297918 Note: it looks as if the data grows by 12288 bytes but this is not true, it does not actually grow. But .data starts with ALIGN(THREAD_SIZE) and since .text shrinks the padding grows, and thus .data grows too as it seen by /bin/size. diff System.map: - ffffffff81510000 D _sdata - ffffffff81510000 D init_thread_union + ffffffff81509000 D _sdata + ffffffff8150c000 D init_thread_union Perhaps we can change vmlinux.lds.S to .data itself, so that /bin/size can't "wrongly" report that .data grows if .text shinks. Signed-off-by:
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Pranith Kumar authored
This commit uses true/false instead of 1/0 for bool types in rcu_gp_fqs() and force_qs_rnp(). Signed-off-by:
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Pranith Kumar authored
Return true instead of 1 in rcu_lockdep_current_cpu_online() as this has bool as return type. Signed-off-by:
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Pranith Kumar authored
Return a bool type instead of 0 in rcu_try_advance_all_cbs(). Signed-off-by:
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Pranith Kumar authored
Use a bool type for return in rcu_is_watching(). Signed-off-by:
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Pranith Kumar authored
fix sparse warning about rcu_batches_completed_preempt() being non-static by marking it as static Signed-off-by:
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Pranith Kumar authored
Change the remaining uses of ACCESS_ONCE() so that each ACCESS_ONCE() either does a load or a store, but not both. Signed-off-by:
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