- 08 6月, 2017 39 次提交
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由 Paul E. McKenney 提交于
Comments can be helpful, but assertions carry more force. This commit therefore adds lockdep_assert_held() and RCU_LOCKDEP_WARN() calls to enforce lock-held and interrupt-disabled preconditions. Reported-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
This commit makes srcu_bootup_announce() check for non-default values of the auto-expedite holdoff time exp_holdoff and print a message if so. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Because exp_holdoff is not used outside of srcutree.c, it can be static. This commit therefore makes this change. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit updates rcu_bootup_announce_oddness() to check additional Kconfig options and module/boot parameters. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit adds a rcupdate_announce_bootup_oddness() function to print out non-default values of significant kernel boot parameter settings to aid in debugging. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit adds WARN_ON_ONCE() calls that trigger if either rcu_sched_qs() or rcu_bh_qs() are invoked with preemption enabled. In the immortal words of Peter Zijlstra: "these are much harder to ignore than comments". Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit classifies tail recursion as an alternative way to write a loop, with similar limitations. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit documents the auto-expediting requirement satisfied by commits 2da4b2a7 ("srcu: Expedite first synchronize_srcu() when idle") and 22607d66 ("srcu: Specify auto-expedite holdoff time"). Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Currently, when running from a git archive, the testid.txt file contains only the branch name, the output of "git status", and the SHA-1 of the current HEAD. This is useful, but does not uniquely identify the source code that was built. This commit therefore adds the output of "git diff HEAD", which means that if two testid.txt files compare equal, they correspond to exactly the same source code. Give or take the possibility of SHA-1 collisions, that is. ;-) Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit adds a writer_holdoff boot parameter to rcuperf, which is intended to be used to test Tree SRCU's auto-expediting. This boot parameter is in microseconds, and defaults to zero (that is, disabled). Set it to a bit larger than srcutree.exp_holdoff, keeping the nanosecond/microsecond conversion, to force Tree SRCU to auto-expedite more aggressively. This commit also adds documentation for this parameter, and fixes some alphabetization while in the neighborhood. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Priyalee Kushwaha 提交于
Most OS distribution have awk in /usr/bin not in /bin Without this patch, kernel-devsrc fails to build as runtime dependency for srcu-cbmc script /bin/awk is not found. Signed-off-by: NKushwaha, Priyalee <priyalee.kushwaha@intel.com> Acked-by: NLance Roy <ldr709@gmail.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Common-case use of rcuperf must set rcuperf.nreaders=0 and if not built as a module, rcuperf.shutdown. This commit therefore sets the default for rcuperf.nreaders to zero and sets the default for rcuperf.shutdown to zero if rcuperf is built as a module and to one otherwise. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit rearranges Tiny SRCU's srcu_struct structure, substitutes u8 for bool, and shrinks counters down to short. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Given that the plan is to retire Classic SRCU in the near future, this commit reduces the number of CPUs dedicated to testing Classic SRCU. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Currently, the only way to tell whether a given kernel is running Classic, Tiny, or Tree SRCU is to look at the .config file, which can easily be lost or associated with the wrong kernel. This commit therefore has Classic and Tree SRCU identify themselves at boot time. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit adds a TINY rcuperf test scenario, which allows performance testing of Tiny RCU and Tiny SRCU. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Stan Drozd 提交于
This commit changes "architecure" to the correct spelling, "architecture". Signed-off-by: NStan Drozd <drozdziak1@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
There is material describing the ordering guarantees provided by spin_unlock_wait(), but it is not necessarily easy to find. This commit therefore adds a docbook header comment to this function informally describing its semantics. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: NPeter Zijlstra <peterz@infradead.org>
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由 Paul E. McKenney 提交于
This commit explicitly states that surrounding a non-value-returning atomic read-modify atomic operations provides full ordering, just as is provided by value-returning atomic read-modify-write operations. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit adds a perf_type of "srcud", which species that rcuperf test SRCU on a dynamically initialized srcu_struct. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
There was a time when the expedited grace-period primitives (synchronize_rcu_expedited(), synchronize_rcu_bh_expedited(), and synchronize_sched_expedited()) used rather antisocial kernel facilities like try_stop_cpus(). However, they have since been housebroken to use only single-CPU IPIs, and typically cause less disturbance than a scheduling-clock interrupt. Furthermore, this disturbance can be eliminated entirely using NO_HZ_FULL on the one hand or the rcupdate.rcu_normal boot parameter on the other. This commit therefore removes checkpatch's complaints about use of the expedited RCU primitives. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
The sync_rcu_preempt_exp_done() function returns a logical expression, but its return type is nevertheless int. This commit therefore changes the return type to bool. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit adds a Kconfig-fragment file for Classic SRCU to ease performance comparisons with Tree SRCU. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit upgrades rcuperf so that it can do performance testing on asynchronous grace-period primitives such as call_srcu(). There is a new rcuperf.gp_async module parameter that specifies this new behavior, with the pre-existing rcuperf.gp_exp testing expedited grace periods such as synchronize_rcu_expedited, and with the default being to test synchronous non-expedited grace periods such as synchronize_rcu(). There is also a new rcuperf.gp_async_max module parameter that specifies the maximum number of outstanding callbacks per writer kthread, defaulting to 1,000. When this limit is exceeded, the writer thread invokes the appropriate flavor of rcu_barrier() to wait for callbacks to drain. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Removed the redundant initialization noted by Arnd Bergmann. ]
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由 Paul E. McKenney 提交于
The synchronize_kernel() primitive was removed in favor of synchronize_sched() more than a decade ago, and it seems likely that rather few kernel hackers are familiar with it. Its continued presence is therefore providing more confusion than enlightenment. This commit therefore removes the reference from the synchronize_sched() header comment, and adds the corresponding information to the synchronize_rcu(0 header comment. Reported-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
The TREE and TREE54 rcuperf scenarios' Kconfig fragment files specified conflicting values for CONFIG_RCU_TRACE. This commit therefore removes the =n line in favor of the =y line. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Current rcuperf startup checks to see if the user asked to measure only expedited grace periods, yet constrained all grace periods to be normal, or if the user asked to measure only normal grace periods, yet constrained all grace periods to be expedited. Useless tests of this sort are aborted. Unfortunately, making RCU work through the mid-boot dead zone [1] puts RCU into expedited-only mode during that zone. Which happens to also be the exact time that rcuperf carries out the aforementioned check. So if the user asks rcuperf to measure only normal grace periods (the default), rcuperf will now always complain and terminate the test. This commit therefore moves the checks to rcu_perf_cleanup(). This has the disadvantage of failing to abort useless tests, but avoids the need to create yet another kthread and the need to do fiddly checks involving the holdoff time. (Yes, another approach is to do the checks in a late-stage init function, but that would require some way to communicate badness to rcuperf's kthreads, and seems not worth the bother.) [1] https://lwn.net/Articles/716148/Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Although preemptible RCU allows its read-side critical sections to be preempted, general blocking is forbidden. The reason for this is that excessive preemption times can be handled by CONFIG_RCU_BOOST=y, but a voluntarily blocked task doesn't care how high you boost its priority. Because preemptible RCU is a global mechanism, one ill-behaved reader hurts everyone. Hence the prohibition against general blocking in RCU-preempt read-side critical sections. Preemption yes, blocking no. This commit enforces this prohibition. There is a special exception for the -rt patchset (which they kindly volunteered to implement): It is OK to block (as opposed to merely being preempted) within an RCU-preempt read-side critical section, but only if the blocking is subject to priority inheritance. This exception permits CONFIG_RCU_BOOST=y to get -rt RCU readers out of trouble. Why doesn't this exception also apply to mainline's rt_mutex? Because of the possibility that someone does general blocking while holding an rt_mutex. Yes, the priority boosting will affect the rt_mutex, but it won't help with the task doing general blocking while holding that rt_mutex. Reported-by: NThomas Gleixner <tglx@linutronix.de> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Earlier versions of Tree SRCU were subject to a counter overflow bug that could theoretically result in too-short grace periods. This commit eliminates this problem by adding an update-side memory barrier. The short explanation is that if the updater sums the unlock counts too late to see a given __srcu_read_unlock() increment, that CPU's next __srcu_read_lock() must see the new value of ->srcu_idx, thus incrementing the other bank of counters. This eliminates the possibility of destructive counter overflow as long as the srcu_read_lock() nesting level does not exceed floor(ULONG_MAX/NR_CPUS/2), which should be an eminently reasonable nesting limit, especially on 64-bit systems. Reported-by: NLance Roy <ldr709@gmail.com> Suggested-by: NLance Roy <ldr709@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
A number of the rcutorture test scenarios were not using the desired Kconfig options because dependencies were preventing the selections in the Kconfig-fragment files from being honored. This commit therefore updates the Kconfig-fragment files to account for these changes in dependencies. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
The rcutorture scripting handles the CONFIG_*_TORTURE_TEST Kconfig options specially, and therefore greps them out of the Kconfig-fragment files. Unfortunately, a poor choice of grep pattern means that the CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP, CONFIG_RCU_TORTURE_TEST_SLOW_INIT, and CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT Kconfig options are also grepped out, preventing rcutorture from using them. This commit therefore fixes the offending grep pattern to focus only on the CONFIG_*_TORTURE_TEST Kconfig options. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Currently rcu_barrier() uses call_rcu() to enqueue new callbacks on each CPU with a non-empty callback list. This works, but means that rcu_barrier() forces grace periods that are not otherwise needed. The key point is that rcu_barrier() never needs to wait for a grace period, but instead only for all pre-existing callbacks to be invoked. This means that rcu_barrier()'s new callbacks should be placed in the callback-list segment containing the last pre-existing callback. This commit makes this change using the new rcu_segcblist_entrain() function. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
A robust combination of paranoia and cowardice has resulted in retaining Classic SRCU (CONFIG_CLASSIC_SRCU) as a backup for the shiny new Tiny and Tree SRCU implementations. If it is to be a viable backup, it of course needs to be tested. This commit therefore adds an rcutorture scenario named SRCU-C for Classic SRCU. This commit also adds this scenario to the set that are run by default. Once sufficient good experience has accumulated for Tiny and Tree SRCU, this test will be removed, along with the Classic SRCU implementation itself. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit adds an SRCU-t rcutorture scenario for the new Tiny SRCU implementation, removing the need to pass the --bootargs parameter to kvm.sh to run Tiny SRCU tests. This commit also adds SRCU-t to the set of scenarios that are run by default. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Kconfig "select" clauses can defeat Kconfig-fragment file attempts to clear a given Kconfig variable, and dependencies can defeat attempts to set a given Kconfig variable. Because "select" clauses and dependencies can be added at any time, there needs to be a way to verify that the Kconfig-fragment file's requests were honored. And there is, except that it is buggy. This commit therefore provides the needed fix. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit adds a test for a three-level srcu_node tree for Tree SRCU in the existing SRCU-P scenario. This requires enabling CONFIG_RCU_EXPERT, so the CONFIG_RCU_EXPERT=n scenario is now SRCU-N. The reason for using SRCU-P for the tall tree is that preemption raises the possibility of locating more bugs than does the non-preemptive SRCU-N. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Back when SRCU was simpler, there wasn't much need for lockdep. However, with Tree SRCU, it is needed. This commit therefore adds CONFIG_PROVE_LOCKING to the SRCU-P scenario. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paolo Bonzini 提交于
Linu Cherian reported a WARN in cleanup_srcu_struct() when shutting down a guest running iperf on a VFIO assigned device. This happens because irqfd_wakeup() calls srcu_read_lock(&kvm->irq_srcu) in interrupt context, while a worker thread does the same inside kvm_set_irq(). If the interrupt happens while the worker thread is executing __srcu_read_lock(), updates to the Classic SRCU ->lock_count[] field or the Tree SRCU ->srcu_lock_count[] field can be lost. The docs say you are not supposed to call srcu_read_lock() and srcu_read_unlock() from irq context, but KVM interrupt injection happens from (host) interrupt context and it would be nice if SRCU supported the use case. KVM is using SRCU here not really for the "sleepable" part, but rather due to its IPI-free fast detection of grace periods. It is therefore not desirable to switch back to RCU, which would effectively revert commit 719d93cd ("kvm/irqchip: Speed up KVM_SET_GSI_ROUTING", 2014-01-16). However, the docs are overly conservative. You can have an SRCU instance only has users in irq context, and you can mix process and irq context as long as process context users disable interrupts. In addition, __srcu_read_unlock() actually uses this_cpu_dec() on both Tree SRCU and Classic SRCU. For those two implementations, only srcu_read_lock() is unsafe. When Classic SRCU's __srcu_read_unlock() was changed to use this_cpu_dec(), in commit 5a41344a ("srcu: Simplify __srcu_read_unlock() via this_cpu_dec()", 2012-11-29), __srcu_read_lock() did two increments. Therefore it kept __this_cpu_inc(), with preempt_disable/enable in the caller. Tree SRCU however only does one increment, so on most architectures it is more efficient for __srcu_read_lock() to use this_cpu_inc(), and any performance differences appear to be down in the noise. Cc: stable@vger.kernel.org Fixes: 719d93cd ("kvm/irqchip: Speed up KVM_SET_GSI_ROUTING") Reported-by: NLinu Cherian <linuc.decode@gmail.com> Suggested-by: NLinu Cherian <linuc.decode@gmail.com> Cc: kvm@vger.kernel.org Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paolo Bonzini 提交于
Linu Cherian reported a WARN in cleanup_srcu_struct() when shutting down a guest running iperf on a VFIO assigned device. This happens because irqfd_wakeup() calls srcu_read_lock(&kvm->irq_srcu) in interrupt context, while a worker thread does the same inside kvm_set_irq(). If the interrupt happens while the worker thread is executing __srcu_read_lock(), updates to the Classic SRCU ->lock_count[] field or the Tree SRCU ->srcu_lock_count[] field can be lost. The docs say you are not supposed to call srcu_read_lock() and srcu_read_unlock() from irq context, but KVM interrupt injection happens from (host) interrupt context and it would be nice if SRCU supported the use case. KVM is using SRCU here not really for the "sleepable" part, but rather due to its IPI-free fast detection of grace periods. It is therefore not desirable to switch back to RCU, which would effectively revert commit 719d93cd ("kvm/irqchip: Speed up KVM_SET_GSI_ROUTING", 2014-01-16). However, the docs are overly conservative. You can have an SRCU instance only has users in irq context, and you can mix process and irq context as long as process context users disable interrupts. In addition, __srcu_read_unlock() actually uses this_cpu_dec() on both Tree SRCU and Classic SRCU. For those two implementations, only srcu_read_lock() is unsafe. When Classic SRCU's __srcu_read_unlock() was changed to use this_cpu_dec(), in commit 5a41344a ("srcu: Simplify __srcu_read_unlock() via this_cpu_dec()", 2012-11-29), __srcu_read_lock() did two increments. Therefore it kept __this_cpu_inc(), with preempt_disable/enable in the caller. Tree SRCU however only does one increment, so on most architectures it is more efficient for __srcu_read_lock() to use this_cpu_inc(), and any performance differences appear to be down in the noise. Unlike Classic and Tree SRCU, Tiny SRCU does increments and decrements on a single variable. Therefore, as Peter Zijlstra pointed out, Tiny SRCU's implementation already supports mixed-context use of srcu_read_lock() and srcu_read_unlock(), at least as long as uses of srcu_read_lock() and srcu_read_unlock() in each handler are nested and paired properly. In other words, it is still illegal to (say) invoke srcu_read_lock() in an interrupt handler and to invoke the matching srcu_read_unlock() in a softirq handler. Therefore, the only change required for Tiny SRCU is to its comments. Fixes: 719d93cd ("kvm/irqchip: Speed up KVM_SET_GSI_ROUTING") Reported-by: NLinu Cherian <linuc.decode@gmail.com> Suggested-by: NLinu Cherian <linuc.decode@gmail.com> Cc: kvm@vger.kernel.org Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NPaolo Bonzini <pbonzini@redhat.com>
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- 05 6月, 2017 1 次提交
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由 Linus Torvalds 提交于
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