- 03 5月, 2012 1 次提交
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由 Paul E. McKenney 提交于
Currently, PREEMPT_RCU readers are enqueued upon entry to the scheduler. This is inefficient because enqueuing is required only if there is a context switch, and entry to the scheduler does not guarantee a context switch. The commit therefore moves the enqueuing to immediately precede the call to switch_to() from the scheduler. Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 24 3月, 2012 1 次提交
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由 Jan Beulich 提交于
Due to the alignment of following variables, these typically consume more than just the single byte that 'bool' requires, and as there are a few hundred instances, the cache pollution (not so much the waste of memory) sums up. Put these variables into their own section, outside of any half way frequently used memory range. Do the same also to the __warned variable of rcu_lockdep_assert(). (Don't, however, include the ones used by printk_once() and alike, as they can potentially be hot.) Signed-off-by: NJan Beulich <jbeulich@suse.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 05 3月, 2012 1 次提交
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由 Paul Gortmaker 提交于
If a header file is making use of BUG, BUG_ON, BUILD_BUG_ON, or any other BUG variant in a static inline (i.e. not in a #define) then that header really should be including <linux/bug.h> and not just expecting it to be implicitly present. We can make this change risk-free, since if the files using these headers didn't have exposure to linux/bug.h already, they would have been causing compile failures/warnings. Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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- 22 2月, 2012 6 次提交
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由 Paul E. McKenney 提交于
RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden in the inner idle loop, that is, between the rcu_idle_enter() and the rcu_idle_exit() -- RCU will happily ignore any such read-side critical sections. However, things like powertop need tracepoints in the inner idle loop. This commit therefore provides an RCU_NONIDLE() macro that can be used to wrap code in the idle loop that requires RCU read-side critical sections. Suggested-by: NSteven Rostedt <rostedt@goodmis.org> Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org> Acked-by: NDeepthi Dharwar <deepthi@linux.vnet.ibm.com>
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由 Heiko Carstens 提交于
The WARN_ON_ONCE() in rcu_lock_acquire() results in infinite recursion on S390, and also doesn't print very much information. Remove this. Updated patch to add lockdep-RCU assertions to RCU's read-side primitives. Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Although it is legal to use RCU during early boot, it is anything but legal to use RCU at runtime from an offlined CPU. After all, RCU explicitly ignores offlined CPUs. This commit therefore adds checks for runtime use of RCU from offlined CPUs. These checks are not perfect, in particular, they can be subverted through use of things like rcu_dereference_raw(). Note that it is not possible to put checks in rcu_read_lock() and friends due to the fact that these primitives are used in code that might be used under either RCU or lock-based protection, which means that checking rcu_read_lock() gets you fat piles of false positives. Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
There is no convenient expression for rcu_deference_protected() when it is used in tearing down multilinked structures following a grace period. For example, suppose that an element containing an RCU-protected pointer to a second element is removed from an enclosing RCU-protected data structure, then the write-side lock is released, and finally synchronize_rcu() is invoked to wait for a grace period. Then it is necessary to traverse the pointer in order to free up the second element. But we are not in an RCU read-side critical section and we are holding no locks, so the usual rcu_dereference_check() and rcu_dereference_protected() primitives are not appropriate. Neither is rcu_dereference_raw(), as it is intended for use in data structures where the user defines the locking design (for example, list_head). So this responsibility is added to rcu_access_pointer()'s list, and this commit updates rcu_assign_pointer()'s header comment accordingly. Suggested-by: NDavid Howells <dhowells@redhat.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: NDavid Howells <dhowells@redhat.com>
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由 Paul E. McKenney 提交于
Although it is OK to be preempted in an RCU read-side critical section for TREE_PREEMPT_RCU, it is definitely not OK to be preempted, block, or might_sleep() within an RCU read-side critical section for TREE_RCU. Unfortunately, rcu_might_sleep() currently only checks for RCU-bh and RCU-sched read-side critical sections. This commit therefore makes rcu_might_sleep() check for RCU read-side critical sections, but only in TREE_RCU builds. Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
When CONFIG_RCU_FAST_NO_HZ is enabled, RCU will allow a given CPU to enter dyntick-idle mode even if it still has RCU callbacks queued. RCU avoids system hangs in this case by scheduling a timer for several jiffies in the future. However, if all of the callbacks on that CPU are from kfree_rcu(), there is no reason to wake the CPU up, as it is not a problem to defer freeing of memory. This commit therefore tracks the number of callbacks on a given CPU that are from kfree_rcu(), and avoids scheduling the timer if all of a given CPU's callbacks are from kfree_rcu(). Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 12 12月, 2011 6 次提交
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由 Paul E. McKenney 提交于
The intent is that a given RCU read-side critical section be confined to a single context. For example, it is illegal to invoke rcu_read_lock() in an exception handler and then invoke rcu_read_unlock() from the context of the task that received the exception. Suggested-by: NPeter Zijlstra <peterz@infradead.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Simplify things a bit by substituting the definitions of the single-line rcu_read_acquire(), rcu_read_release(), rcu_read_acquire_bh(), rcu_read_release_bh(), rcu_read_acquire_sched(), and rcu_read_release_sched() functions at their call points. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Frederic Weisbecker 提交于
We are currently able to detect uses of rcu_dereference_check() inside extended quiescent states (such as the RCU-free window in idle). But rcu_read_lock() and friends can be used without rcu_dereference(), so that the earlier commit checking for use of rcu_dereference() and friends while in RCU idle mode miss some error conditions. This commit therefore adds extended quiescent state checking to rcu_read_lock() and friends. Uses of RCU from within RCU-idle mode are totally ignored by RCU, hence the importance of these checks. Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Frederic Weisbecker 提交于
Report that none of the rcu read lock maps are held while in an RCU extended quiescent state (the section between rcu_idle_enter() and rcu_idle_exit()). This helps detect any use of rcu_dereference() and friends from within the section in idle where RCU is not allowed. This way we can guarantee an extended quiescent window where the CPU can be put in dyntick idle mode or can simply aoid to be part of any global grace period completion while in the idle loop. Uses of RCU from such mode are totally ignored by RCU, hence the importance of these checks. Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
Trace the rcutorture RCU accesses and dump the trace buffer when the first failure is detected. Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
Earlier versions of RCU used the scheduling-clock tick to detect idleness by checking for the idle task, but handled idleness differently for CONFIG_NO_HZ=y. But there are now a number of uses of RCU read-side critical sections in the idle task, for example, for tracing. A more fine-grained detection of idleness is therefore required. This commit presses the old dyntick-idle code into full-time service, so that rcu_idle_enter(), previously known as rcu_enter_nohz(), is always invoked at the beginning of an idle loop iteration. Similarly, rcu_idle_exit(), previously known as rcu_exit_nohz(), is always invoked at the end of an idle-loop iteration. This allows the idle task to use RCU everywhere except between consecutive rcu_idle_enter() and rcu_idle_exit() calls, in turn allowing architecture maintainers to specify exactly where in the idle loop that RCU may be used. Because some of the userspace upcall uses can result in what looks to RCU like half of an interrupt, it is not possible to expect that the irq_enter() and irq_exit() hooks will give exact counts. This patch therefore expands the ->dynticks_nesting counter to 64 bits and uses two separate bitfields to count process/idle transitions and interrupt entry/exit transitions. It is presumed that userspace upcalls do not happen in the idle loop or from usermode execution (though usermode might do a system call that results in an upcall). The counter is hard-reset on each process/idle transition, which avoids the interrupt entry/exit error from accumulating. Overflow is avoided by the 64-bitness of the ->dyntick_nesting counter. This commit also adds warnings if a non-idle task asks RCU to enter idle state (and these checks will need some adjustment before applying Frederic's OS-jitter patches (http://lkml.org/lkml/2011/10/7/246). In addition, validation of ->dynticks and ->dynticks_nesting is added. Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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- 29 9月, 2011 8 次提交
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由 Paul E. McKenney 提交于
We only need to constrain the compiler if we are actually exiting the top-level RCU read-side critical section. This commit therefore moves the first barrier() cal in __rcu_read_unlock() to inside the "if" statement, thus avoiding needless register flushes for inner rcu_read_unlock() calls. Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
The differences between rcu_assign_pointer() and RCU_INIT_POINTER() are subtle, and it is easy to use the the cheaper RCU_INIT_POINTER() when the more-expensive rcu_assign_pointer() should have been used instead. The consequences of this mistake are quite severe. This commit therefore carefully lays out the situations in which it it permissible to use RCU_INIT_POINTER(). Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Eric Dumazet 提交于
Recent changes to gcc give warning messages on rcu_assign_pointers()'s checks that allow it to determine when it is OK to omit the memory barrier. Stephen Hemminger tried a number of gcc tricks to silence this warning, but #pragmas and CPP macros do not work together in the way that would be required to make this work. However, we now have RCU_INIT_POINTER(), which already omits this memory barrier, and which therefore may be used when assigning NULL to an RCU-protected pointer that is accessible to readers. This commit therefore makes rcu_assign_pointer() unconditionally emit the memory barrier. Reported-by: NStephen Hemminger <shemminger@vyatta.com> Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com> Acked-by: NDavid S. Miller <davem@davemloft.net> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
The rcu_dereference_bh_protected() and rcu_dereference_sched_protected() macros are synonyms for rcu_dereference_protected() and are not used anywhere in mainline. This commit therefore removes them. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
There was recently some controversy about the overhead of invoking RCU callbacks. Add TRACE_EVENT()s to obtain fine-grained timings for the start and stop of a batch of callbacks and also for each callback invoked. Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Pull the code that waits for an RCU grace period into a single function, which is then called by synchronize_rcu() and friends in the case of TREE_RCU and TREE_PREEMPT_RCU, and from rcu_barrier() and friends in the case of TINY_RCU and TINY_PREEMPT_RCU. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Take a first step towards untangling Linux kernel header files by placing the struct rcu_head definition into include/linux/types.h and including include/linux/types.h in include/linux/rcupdate.h where struct rcu_head used to be defined. The actual inclusion point for include/linux/types.h is with the rest of the #include directives rather than at the point where struct rcu_head used to be defined, as suggested by Mathieu Desnoyers. Once this is in place, then header files that need only rcu_head can include types.h rather than rcupdate.h. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Acked-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com>
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由 Paul E. McKenney 提交于
Long ago, using TREE_RCU with PREEMPT would result in "scheduling while atomic" diagnostics if you blocked in an RCU read-side critical section. However, PREEMPT now implies TREE_PREEMPT_RCU, which defeats this diagnostic. This commit therefore adds a replacement diagnostic based on PROVE_RCU. Because rcu_lockdep_assert() and lockdep_rcu_dereference() are now being used for things that have nothing to do with rcu_dereference(), rename lockdep_rcu_dereference() to lockdep_rcu_suspicious() and add a third argument that is a string indicating what is suspicious. This third argument is passed in from a new third argument to rcu_lockdep_assert(). Update all calls to rcu_lockdep_assert() to add an informative third argument. Also, add a pair of rcu_lockdep_assert() calls from within rcu_note_context_switch(), one complaining if a context switch occurs in an RCU-bh read-side critical section and another complaining if a context switch occurs in an RCU-sched read-side critical section. These are present only if the PROVE_RCU kernel parameter is enabled. Finally, fix some checkpatch whitespace complaints in lockdep.c. Again, you must enable PROVE_RCU to see these new diagnostics. But you are enabling PROVE_RCU to check out new RCU uses in any case, aren't you? Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 10 6月, 2011 1 次提交
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由 Frederic Weisbecker 提交于
Create a new CONFIG_PREEMPT_COUNT that handles the inc/dec of preempt count offset independently. So that the offset can be updated by preempt_disable() and preempt_enable() even without the need for CONFIG_PREEMPT beeing set. This prepares to make CONFIG_DEBUG_SPINLOCK_SLEEP working with !CONFIG_PREEMPT where it currently doesn't detect code that sleeps inside explicit preemption disabled sections. Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com> Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
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- 06 5月, 2011 3 次提交
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由 Lai Jiangshan 提交于
Many rcu callbacks functions just call kfree() on the base structure. These functions are trivial, but their size adds up, and furthermore when they are used in a kernel module, that module must invoke the high-latency rcu_barrier() function at module-unload time. The kfree_rcu() function introduced by this commit addresses this issue. Rather than encoding a function address in the embedded rcu_head structure, kfree_rcu() instead encodes the offset of the rcu_head structure within the base structure. Because the functions are not allowed in the low-order 4096 bytes of kernel virtual memory, offsets up to 4095 bytes can be accommodated. If the offset is larger than 4095 bytes, a compile-time error will be generated in __kfree_rcu(). If this error is triggered, you can either fall back to use of call_rcu() or rearrange the structure to position the rcu_head structure into the first 4096 bytes. Note that the allowable offset might decrease in the future, for example, to allow something like kmem_cache_free_rcu(). The new kfree_rcu() function can replace code as follows: call_rcu(&p->rcu, simple_kfree_callback); where "simple_kfree_callback()" might be defined as follows: void simple_kfree_callback(struct rcu_head *p) { struct foo *q = container_of(p, struct foo, rcu); kfree(q); } with the following: kfree_rcu(&p->rcu, rcu); Note that the "rcu" is the name of a field in the structure being freed. The reason for using this rather than passing in a pointer to the base structure is that the above approach allows better type checking. This commit is based on earlier work by Lai Jiangshan and Manfred Spraul: Lai's V1 patch: http://lkml.org/lkml/2008/9/18/1 Manfred's patch: http://lkml.org/lkml/2009/1/2/115Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NDavid Howells <dhowells@redhat.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
Verify that rcu_head structures are aligned to a four-byte boundary. This check is enabled by CONFIG_DEBUG_OBJECTS_RCU_HEAD. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
It is not possible to accurately correlate rcutorture output with that of debugfs. This patch therefore adds a debugfs file that prints out the rcutorture version number, permitting easy correlation. Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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- 01 4月, 2011 1 次提交
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由 Paul E. McKenney 提交于
The MCE subsystem needs to sample an RCU-protected index outside of any protection for that index. If this was a pointer, we would use rcu_access_pointer(), but there is no corresponding rcu_access_index(). This commit therefore creates an rcu_access_index() and applies it to MCE. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NZdenek Kabelac <zkabelac@redhat.com>
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- 18 12月, 2010 1 次提交
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由 Tejun Heo 提交于
The fix in commit #6a0cc49 requires more than three concurrent instances of synchronize_sched_expedited() before batching is possible. This patch uses a ticket-counter-like approach that is also not unrelated to Lai Jiangshan's Ring RCU to allow sharing of expedited grace periods even when there are only two concurrent instances of synchronize_sched_expedited(). This commit builds on Tejun's original posting, which may be found at http://lkml.org/lkml/2010/11/9/204, adding memory barriers, avoiding overflow of signed integers (other than via atomic_t), and fixing the detection of batching. Signed-off-by: NTejun Heo <tj@kernel.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 30 11月, 2010 1 次提交
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由 Lai Jiangshan 提交于
The first version of synchronize_sched_expedited() used the migration code in the scheduler, and was therefore implemented in kernel/sched.c. However, the more recent version of this code no longer uses the migration code, so this commit moves it to the main RCU source files. Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 18 11月, 2010 1 次提交
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由 Paul E. McKenney 提交于
If RCU priority boosting is to be meaningful, callback invocation must be boosted in addition to preempted RCU readers. Otherwise, in presence of CPU real-time threads, the grace period ends, but the callbacks don't get invoked. If the callbacks don't get invoked, the associated memory doesn't get freed, so the system is still subject to OOM. But it is not reasonable to priority-boost RCU_SOFTIRQ, so this commit moves the callback invocations to a kthread, which can be boosted easily. Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 06 10月, 2010 1 次提交
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由 Paul E. McKenney 提交于
As suggested by Linus, push the irqs_disabled() down to the rcu_read_lock_bh_held() level so that all callers get the benefit of the correct check. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 24 9月, 2010 1 次提交
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由 Paul E. McKenney 提交于
The current version of the __rcu_access_pointer(), __rcu_dereference_check(), and __rcu_dereference_protected() macros evaluate their "p" argument three times, not counting typeof()s. This is bad news if that argument contains a side effect. This commit therefore evaluates this argument only once in normal kernel builds. However, the straightforward approach defeats sparse's RCU-pointer checking, so when __CHECKER__ is defined, the additional pair of evaluations of the "p" argument are performed in order to permit sparse to detect misuse of RCU-protected pointers. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Arnd Bergmann <arnd@arndb.de>
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- 23 9月, 2010 1 次提交
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由 Eric Dumazet 提交于
rcu_dereference_bh() doesnt know yet about hard irq being disabled, so lockdep can trigger in netpoll_rx() after commit f0f9deae (netpoll: Disable IRQ around RCU dereference in netpoll_rx) Reported-by: NMiles Lane <miles.lane@gmail.com> Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com> Tested-by: NMiles Lane <miles.lane@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 21 8月, 2010 3 次提交
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由 Paul E. McKenney 提交于
The CONFIG_PREEMPT_RCU kernel configuration parameter was recently re-introduced, but as an indication of the type of RCU (preemptible vs. non-preemptible) instead of as selecting a given implementation. This commit uses CONFIG_PREEMPT_RCU to combine duplicate code from include/linux/rcutiny.h and include/linux/rcutree.h into include/linux/rcupdate.h. This commit also combines a few other pieces of duplicate code that have accumulated. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Combine the duplicate definitions of ULONG_CMP_GE(), ULONG_CMP_LT(), and rcu_preempt_depth() into include/linux/rcupdate.h. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
The comment says that blocking is illegal in rcu_read_lock()-style RCU read-side critical sections, which is no longer entirely true given preemptible RCU. This commit provides a fix. Suggested-by: NDavid Miller <davem@davemloft.net> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 20 8月, 2010 3 次提交
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由 Paul E. McKenney 提交于
Implement a small-memory-footprint uniprocessor-only implementation of preemptible RCU. This implementation uses but a single blocked-tasks list rather than the combinatorial number used per leaf rcu_node by TREE_PREEMPT_RCU, which reduces memory consumption and greatly simplifies processing. This version also takes advantage of uniprocessor execution to accelerate grace periods in the case where there are no readers. The general design is otherwise broadly similar to that of TREE_PREEMPT_RCU. This implementation is a step towards having RCU implementation driven off of the SMP and PREEMPT kernel configuration variables, which can happen once this implementation has accumulated sufficient experience. Removed ACCESS_ONCE() from __rcu_read_unlock() and added barrier() as suggested by Steve Rostedt in order to avoid the compiler-reordering issue noted by Mathieu Desnoyers (http://lkml.org/lkml/2010/8/16/183). As can be seen below, CONFIG_TINY_PREEMPT_RCU represents almost 5Kbyte savings compared to CONFIG_TREE_PREEMPT_RCU. Of course, for non-real-time workloads, CONFIG_TINY_RCU is even better. CONFIG_TREE_PREEMPT_RCU text data bss dec filename 13 0 0 13 kernel/rcupdate.o 6170 825 28 7023 kernel/rcutree.o ---- 7026 Total CONFIG_TINY_PREEMPT_RCU text data bss dec filename 13 0 0 13 kernel/rcupdate.o 2081 81 8 2170 kernel/rcutiny.o ---- 2183 Total CONFIG_TINY_RCU (non-preemptible) text data bss dec filename 13 0 0 13 kernel/rcupdate.o 719 25 0 744 kernel/rcutiny.o --- 757 Total Requested-by: NLoïc Minier <loic.minier@canonical.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Mathieu Desnoyers 提交于
RCU heads really don't need to be initialized. Their state before call_rcu() really does not matter. We need to keep init/destroy_rcu_head_on_stack() though, since we want debugobjects to be able to keep track of these objects. Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com> Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com> CC: David S. Miller <davem@davemloft.net> CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> CC: akpm@linux-foundation.org CC: mingo@elte.hu CC: laijs@cn.fujitsu.com CC: dipankar@in.ibm.com CC: josh@joshtriplett.org CC: dvhltc@us.ibm.com CC: niv@us.ibm.com CC: tglx@linutronix.de CC: peterz@infradead.org CC: rostedt@goodmis.org CC: Valdis.Kletnieks@vt.edu CC: dhowells@redhat.com CC: eric.dumazet@gmail.com CC: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
Make it explicit that new RCU read-side critical sections that start after call_rcu() and synchronize_rcu() start might still be running after the end of the relevant grace period. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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