diff options
Diffstat (limited to 'Documentation/RCU')
11 files changed, 66 insertions, 220 deletions
diff --git a/Documentation/RCU/Design/Expedited-Grace-Periods/ExpSchedFlow.svg b/Documentation/RCU/Design/Expedited-Grace-Periods/ExpSchedFlow.svg index e4233ac93c2b..6189ffcc6aff 100644 --- a/Documentation/RCU/Design/Expedited-Grace-Periods/ExpSchedFlow.svg +++ b/Documentation/RCU/Design/Expedited-Grace-Periods/ExpSchedFlow.svg @@ -328,13 +328,13 @@ inkscape:window-height="1148" id="namedview90" showgrid="true" - inkscape:zoom="0.80021373" - inkscape:cx="462.49289" - inkscape:cy="473.6718" + inkscape:zoom="0.69092787" + inkscape:cx="476.34085" + inkscape:cy="712.80957" inkscape:window-x="770" inkscape:window-y="24" inkscape:window-maximized="0" - inkscape:current-layer="g4114-9-3-9" + inkscape:current-layer="g4" inkscape:snap-grids="false" fit-margin-top="5" fit-margin-right="5" @@ -813,14 +813,18 @@ <text sodipodi:linespacing="125%" id="text4110-5-7-6-2-4-0" - y="841.88086" + y="670.74316" x="1460.1007" style="font-size:267.24359131px;font-style:normal;font-weight:normal;text-align:center;line-height:125%;letter-spacing:0px;word-spacing:0px;text-anchor:middle;fill:#000000;fill-opacity:1;stroke:none;font-family:Sans" xml:space="preserve"><tspan - y="841.88086" + y="670.74316" + x="1460.1007" + sodipodi:role="line" + id="tspan4925-1-2-4-5">Request</tspan><tspan + y="1004.7976" x="1460.1007" sodipodi:role="line" - id="tspan4925-1-2-4-5">reched_cpu()</tspan></text> + id="tspan3100">context switch</tspan></text> </g> </g> </svg> diff --git a/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html b/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html index 8e4f873b979f..19e7a5fb6b73 100644 --- a/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html +++ b/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html @@ -72,10 +72,10 @@ will ignore it because idle and offline CPUs are already residing in quiescent states. Otherwise, the expedited grace period will use <tt>smp_call_function_single()</tt> to send the CPU an IPI, which -is handled by <tt>sync_rcu_exp_handler()</tt>. +is handled by <tt>rcu_exp_handler()</tt>. <p> -However, because this is preemptible RCU, <tt>sync_rcu_exp_handler()</tt> +However, because this is preemptible RCU, <tt>rcu_exp_handler()</tt> can check to see if the CPU is currently running in an RCU read-side critical section. If not, the handler can immediately report a quiescent state. @@ -145,19 +145,18 @@ expedited grace period is shown in the following diagram: <p><img src="ExpSchedFlow.svg" alt="ExpSchedFlow.svg" width="55%"> <p> -As with RCU-preempt's <tt>synchronize_rcu_expedited()</tt>, +As with RCU-preempt, RCU-sched's <tt>synchronize_sched_expedited()</tt> ignores offline and idle CPUs, again because they are in remotely detectable quiescent states. -However, the <tt>synchronize_rcu_expedited()</tt> handler -is <tt>sync_sched_exp_handler()</tt>, and because the +However, because the <tt>rcu_read_lock_sched()</tt> and <tt>rcu_read_unlock_sched()</tt> leave no trace of their invocation, in general it is not possible to tell whether or not the current CPU is in an RCU read-side critical section. -The best that <tt>sync_sched_exp_handler()</tt> can do is to check +The best that RCU-sched's <tt>rcu_exp_handler()</tt> can do is to check for idle, on the off-chance that the CPU went idle while the IPI was in flight. -If the CPU is idle, then <tt>sync_sched_exp_handler()</tt> reports +If the CPU is idle, then <tt>rcu_exp_handler()</tt> reports the quiescent state. <p> Otherwise, the handler forces a future context switch by setting the @@ -298,19 +297,18 @@ Instead, the task pushing the grace period forward will include the idle CPUs in the mask passed to <tt>rcu_report_exp_cpu_mult()</tt>. <p> -For RCU-sched, there is an additional check for idle in the IPI -handler, <tt>sync_sched_exp_handler()</tt>. +For RCU-sched, there is an additional check: If the IPI has interrupted the idle loop, then -<tt>sync_sched_exp_handler()</tt> invokes <tt>rcu_report_exp_rdp()</tt> +<tt>rcu_exp_handler()</tt> invokes <tt>rcu_report_exp_rdp()</tt> to report the corresponding quiescent state. <p> For RCU-preempt, there is no specific check for idle in the -IPI handler (<tt>sync_rcu_exp_handler()</tt>), but because +IPI handler (<tt>rcu_exp_handler()</tt>), but because RCU read-side critical sections are not permitted within the -idle loop, if <tt>sync_rcu_exp_handler()</tt> sees that the CPU is within +idle loop, if <tt>rcu_exp_handler()</tt> sees that the CPU is within RCU read-side critical section, the CPU cannot possibly be idle. -Otherwise, <tt>sync_rcu_exp_handler()</tt> invokes +Otherwise, <tt>rcu_exp_handler()</tt> invokes <tt>rcu_report_exp_rdp()</tt> to report the corresponding quiescent state, regardless of whether or not that quiescent state was due to the CPU being idle. @@ -625,6 +623,8 @@ checks, but only during the mid-boot dead zone. <p> With this refinement, synchronous grace periods can now be used from task context pretty much any time during the life of the kernel. +That is, aside from some points in the suspend, hibernate, or shutdown +code path. <h3><a name="Summary"> Summary</a></h3> diff --git a/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html b/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html index e4d94fba6c89..8d21af02b1f0 100644 --- a/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html +++ b/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html @@ -485,13 +485,13 @@ section that the grace period must wait on. noted by <tt>rcu_node_context_switch()</tt> on the left. On the other hand, if the CPU takes a scheduler-clock interrupt while executing in usermode, a quiescent state will be noted by -<tt>rcu_check_callbacks()</tt> on the right. +<tt>rcu_sched_clock_irq()</tt> on the right. Either way, the passage through a quiescent state will be noted in a per-CPU variable. <p>The next time an <tt>RCU_SOFTIRQ</tt> handler executes on this CPU (for example, after the next scheduler-clock -interrupt), <tt>__rcu_process_callbacks()</tt> will invoke +interrupt), <tt>rcu_core()</tt> will invoke <tt>rcu_check_quiescent_state()</tt>, which will notice the recorded quiescent state, and invoke <tt>rcu_report_qs_rdp()</tt>. @@ -651,7 +651,7 @@ to end. These callbacks are identified by <tt>rcu_advance_cbs()</tt>, which is usually invoked by <tt>__note_gp_changes()</tt>. As shown in the diagram below, this invocation can be triggered by -the scheduling-clock interrupt (<tt>rcu_check_callbacks()</tt> on +the scheduling-clock interrupt (<tt>rcu_sched_clock_irq()</tt> on the left) or by idle entry (<tt>rcu_cleanup_after_idle()</tt> on the right, but only for kernels build with <tt>CONFIG_RCU_FAST_NO_HZ=y</tt>). diff --git a/Documentation/RCU/Design/Memory-Ordering/TreeRCU-callback-invocation.svg b/Documentation/RCU/Design/Memory-Ordering/TreeRCU-callback-invocation.svg index 832408313d93..3fcf0c17cef2 100644 --- a/Documentation/RCU/Design/Memory-Ordering/TreeRCU-callback-invocation.svg +++ b/Documentation/RCU/Design/Memory-Ordering/TreeRCU-callback-invocation.svg @@ -349,7 +349,7 @@ font-weight="bold" font-size="192" id="text202-7-5" - style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_check_callbacks()</text> + style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_sched_clock_irq()</text> <rect x="7069.6187" y="5087.4678" diff --git a/Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp.svg b/Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp.svg index acd73c7ad0f4..2bcd742d6e49 100644 --- a/Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp.svg +++ b/Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp.svg @@ -3902,7 +3902,7 @@ font-style="normal" y="-4418.6582" x="3745.7725" - xml:space="preserve">rcu_check_callbacks()</text> + xml:space="preserve">rcu_sched_clock_irq()</text> </g> <g transform="translate(-850.30204,55463.106)" @@ -3924,7 +3924,7 @@ font-style="normal" y="-4418.6582" x="3745.7725" - xml:space="preserve">rcu_process_callbacks()</text> + xml:space="preserve">rcu_core()</text> <text style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier" id="text202-7-5-3-27-0" @@ -3933,7 +3933,7 @@ font-style="normal" y="-4165.7954" x="3745.7725" - xml:space="preserve">rcu_check_quiescent_state())</text> + xml:space="preserve">rcu_check_quiescent_state()</text> <text style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier" id="text202-7-5-3-27-0-9" @@ -4968,7 +4968,7 @@ font-weight="bold" font-size="192" id="text202-7-5-19" - style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_check_callbacks()</text> + style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_sched_clock_irq()</text> <rect x="5314.2671" y="82817.688" diff --git a/Documentation/RCU/Design/Memory-Ordering/TreeRCU-qs.svg b/Documentation/RCU/Design/Memory-Ordering/TreeRCU-qs.svg index 149bec2a4493..779c9ac31a52 100644 --- a/Documentation/RCU/Design/Memory-Ordering/TreeRCU-qs.svg +++ b/Documentation/RCU/Design/Memory-Ordering/TreeRCU-qs.svg @@ -775,7 +775,7 @@ font-style="normal" y="-4418.6582" x="3745.7725" - xml:space="preserve">rcu_check_callbacks()</text> + xml:space="preserve">rcu_sched_clock_irq()</text> </g> <g transform="translate(399.7744,828.86448)" @@ -797,7 +797,7 @@ font-style="normal" y="-4418.6582" x="3745.7725" - xml:space="preserve">rcu_process_callbacks()</text> + xml:space="preserve">rcu_core()</text> <text style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier" id="text202-7-5-3-27-0" @@ -806,7 +806,7 @@ font-style="normal" y="-4165.7954" x="3745.7725" - xml:space="preserve">rcu_check_quiescent_state())</text> + xml:space="preserve">rcu_check_quiescent_state()</text> <text style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier" id="text202-7-5-3-27-0-9" diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index 9fca73e03a98..5a9238a2883c 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.html +++ b/Documentation/RCU/Design/Requirements/Requirements.html @@ -3099,7 +3099,7 @@ If you block forever in one of a given domain's SRCU read-side critical sections, then that domain's grace periods will also be blocked forever. Of course, one good way to block forever is to deadlock, which can happen if any operation in a given domain's SRCU read-side critical -section can block waiting, either directly or indirectly, for that domain's +section can wait, either directly or indirectly, for that domain's grace period to elapse. For example, this results in a self-deadlock: @@ -3139,12 +3139,18 @@ API, which, in combination with <tt>srcu_read_unlock()</tt>, guarantees a full memory barrier. <p> -Also unlike other RCU flavors, SRCU's callbacks-wait function -<tt>srcu_barrier()</tt> may be invoked from CPU-hotplug notifiers, -though this is not necessarily a good idea. -The reason that this is possible is that SRCU is insensitive -to whether or not a CPU is online, which means that <tt>srcu_barrier()</tt> -need not exclude CPU-hotplug operations. +Also unlike other RCU flavors, <tt>synchronize_srcu()</tt> may <b>not</b> +be invoked from CPU-hotplug notifiers, due to the fact that SRCU grace +periods make use of timers and the possibility of timers being temporarily +“stranded” on the outgoing CPU. +This stranding of timers means that timers posted to the outgoing CPU +will not fire until late in the CPU-hotplug process. +The problem is that if a notifier is waiting on an SRCU grace period, +that grace period is waiting on a timer, and that timer is stranded on the +outgoing CPU, then the notifier will never be awakened, in other words, +deadlock has occurred. +This same situation of course also prohibits <tt>srcu_barrier()</tt> +from being invoked from CPU-hotplug notifiers. <p> SRCU also differs from other RCU flavors in that SRCU's expedited and diff --git a/Documentation/RCU/lockdep-splat.txt b/Documentation/RCU/lockdep-splat.txt index 238e9f61352f..9c015976b174 100644 --- a/Documentation/RCU/lockdep-splat.txt +++ b/Documentation/RCU/lockdep-splat.txt @@ -14,9 +14,9 @@ being the real world and all that. So let's look at an example RCU lockdep splat from 3.0-rc5, one that has long since been fixed: -=============================== -[ INFO: suspicious RCU usage. ] -------------------------------- +============================= +WARNING: suspicious RCU usage +----------------------------- block/cfq-iosched.c:2776 suspicious rcu_dereference_protected() usage! other info that might help us debug this: @@ -24,11 +24,11 @@ other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 3 locks held by scsi_scan_6/1552: - #0: (&shost->scan_mutex){+.+.+.}, at: [<ffffffff8145efca>] + #0: (&shost->scan_mutex){+.+.}, at: [<ffffffff8145efca>] scsi_scan_host_selected+0x5a/0x150 - #1: (&eq->sysfs_lock){+.+...}, at: [<ffffffff812a5032>] + #1: (&eq->sysfs_lock){+.+.}, at: [<ffffffff812a5032>] elevator_exit+0x22/0x60 - #2: (&(&q->__queue_lock)->rlock){-.-...}, at: [<ffffffff812b6233>] + #2: (&(&q->__queue_lock)->rlock){-.-.}, at: [<ffffffff812b6233>] cfq_exit_queue+0x43/0x190 stack backtrace: diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 073dbc12d1ea..1ab70c37921f 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -219,17 +219,18 @@ an estimate of the total number of RCU callbacks queued across all CPUs In kernels with CONFIG_RCU_FAST_NO_HZ, more information is printed for each CPU: - 0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 softirq=82/543 last_accelerate: a345/d342 nonlazy_posted: 25 .D + 0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 softirq=82/543 last_accelerate: a345/d342 Nonlazy posted: ..D The "last_accelerate:" prints the low-order 16 bits (in hex) of the jiffies counter when this CPU last invoked rcu_try_advance_all_cbs() from rcu_needs_cpu() or last invoked rcu_accelerate_cbs() from -rcu_prepare_for_idle(). The "nonlazy_posted:" prints the number -of non-lazy callbacks posted since the last call to rcu_needs_cpu(). -Finally, an "L" indicates that there are currently no non-lazy callbacks -("." is printed otherwise, as shown above) and "D" indicates that -dyntick-idle processing is enabled ("." is printed otherwise, for example, -if disabled via the "nohz=" kernel boot parameter). +rcu_prepare_for_idle(). The "Nonlazy posted:" indicates lazy-callback +status, so that an "l" indicates that all callbacks were lazy at the start +of the last idle period and an "L" indicates that there are currently +no non-lazy callbacks (in both cases, "." is printed otherwise, as +shown above) and "D" indicates that dyntick-idle processing is enabled +("." is printed otherwise, for example, if disabled via the "nohz=" +kernel boot parameter). If the grace period ends just as the stall warning starts printing, there will be a spurious stall-warning message, which will include diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt index 55918b54808b..a41a0384d20c 100644 --- a/Documentation/RCU/torture.txt +++ b/Documentation/RCU/torture.txt @@ -10,173 +10,8 @@ status messages via printk(), which can be examined via the dmesg command (perhaps grepping for "torture"). The test is started when the module is loaded, and stops when the module is unloaded. - -MODULE PARAMETERS - -This module has the following parameters: - -fqs_duration Duration (in microseconds) of artificially induced bursts - of force_quiescent_state() invocations. In RCU - implementations having force_quiescent_state(), these - bursts help force races between forcing a given grace - period and that grace period ending on its own. - -fqs_holdoff Holdoff time (in microseconds) between consecutive calls - to force_quiescent_state() within a burst. - -fqs_stutter Wait time (in seconds) between consecutive bursts - of calls to force_quiescent_state(). - -gp_normal Make the fake writers use normal synchronous grace-period - primitives. - -gp_exp Make the fake writers use expedited synchronous grace-period - primitives. If both gp_normal and gp_exp are set, or - if neither gp_normal nor gp_exp are set, then randomly - choose the primitive so that about 50% are normal and - 50% expedited. By default, neither are set, which - gives best overall test coverage. - -irqreader Says to invoke RCU readers from irq level. This is currently - done via timers. Defaults to "1" for variants of RCU that - permit this. (Or, more accurately, variants of RCU that do - -not- permit this know to ignore this variable.) - -n_barrier_cbs If this is nonzero, RCU barrier testing will be conducted, - in which case n_barrier_cbs specifies the number of - RCU callbacks (and corresponding kthreads) to use for - this testing. The value cannot be negative. If you - specify this to be non-zero when torture_type indicates a - synchronous RCU implementation (one for which a member of - the synchronize_rcu() rather than the call_rcu() family is - used -- see the documentation for torture_type below), an - error will be reported and no testing will be carried out. - -nfakewriters This is the number of RCU fake writer threads to run. Fake - writer threads repeatedly use the synchronous "wait for - current readers" function of the interface selected by - torture_type, with a delay between calls to allow for various - different numbers of writers running in parallel. - nfakewriters defaults to 4, which provides enough parallelism - to trigger special cases caused by multiple writers, such as - the synchronize_srcu() early return optimization. - -nreaders This is the number of RCU reading threads supported. - The default is twice the number of CPUs. Why twice? - To properly exercise RCU implementations with preemptible - read-side critical sections. - -onoff_interval - The number of seconds between each attempt to execute a - randomly selected CPU-hotplug operation. Defaults to - zero, which disables CPU hotplugging. In HOTPLUG_CPU=n - kernels, rcutorture will silently refuse to do any - CPU-hotplug operations regardless of what value is - specified for onoff_interval. - -onoff_holdoff The number of seconds to wait until starting CPU-hotplug - operations. This would normally only be used when - rcutorture was built into the kernel and started - automatically at boot time, in which case it is useful - in order to avoid confusing boot-time code with CPUs - coming and going. - -shuffle_interval - The number of seconds to keep the test threads affinitied - to a particular subset of the CPUs, defaults to 3 seconds. - Used in conjunction with test_no_idle_hz. - -shutdown_secs The number of seconds to run the test before terminating - the test and powering off the system. The default is - zero, which disables test termination and system shutdown. - This capability is useful for automated testing. - -stall_cpu The number of seconds that a CPU should be stalled while - within both an rcu_read_lock() and a preempt_disable(). - This stall happens only once per rcutorture run. - If you need multiple stalls, use modprobe and rmmod to - repeatedly run rcutorture. The default for stall_cpu - is zero, which prevents rcutorture from stalling a CPU. - - Note that attempts to rmmod rcutorture while the stall - is ongoing will hang, so be careful what value you - choose for this module parameter! In addition, too-large - values for stall_cpu might well induce failures and - warnings in other parts of the kernel. You have been - warned! - -stall_cpu_holdoff - The number of seconds to wait after rcutorture starts - before stalling a CPU. Defaults to 10 seconds. - -stat_interval The number of seconds between output of torture - statistics (via printk()). Regardless of the interval, - statistics are printed when the module is unloaded. - Setting the interval to zero causes the statistics to - be printed -only- when the module is unloaded, and this - is the default. - -stutter The length of time to run the test before pausing for this - same period of time. Defaults to "stutter=5", so as - to run and pause for (roughly) five-second intervals. - Specifying "stutter=0" causes the test to run continuously - without pausing, which is the old default behavior. - -test_boost Whether or not to test the ability of RCU to do priority - boosting. Defaults to "test_boost=1", which performs - RCU priority-inversion testing only if the selected - RCU implementation supports priority boosting. Specifying - "test_boost=0" never performs RCU priority-inversion - testing. Specifying "test_boost=2" performs RCU - priority-inversion testing even if the selected RCU - implementation does not support RCU priority boosting, - which can be used to test rcutorture's ability to - carry out RCU priority-inversion testing. - -test_boost_interval - The number of seconds in an RCU priority-inversion test - cycle. Defaults to "test_boost_interval=7". It is - usually wise for this value to be relatively prime to - the value selected for "stutter". - -test_boost_duration - The number of seconds to do RCU priority-inversion testing - within any given "test_boost_interval". Defaults to - "test_boost_duration=4". - -test_no_idle_hz Whether or not to test the ability of RCU to operate in - a kernel that disables the scheduling-clock interrupt to - idle CPUs. Boolean parameter, "1" to test, "0" otherwise. - Defaults to omitting this test. - -torture_type The type of RCU to test, with string values as follows: - - "rcu": rcu_read_lock(), rcu_read_unlock() and call_rcu(), - along with expedited, synchronous, and polling - variants. - - "rcu_bh": rcu_read_lock_bh(), rcu_read_unlock_bh(), and - call_rcu_bh(), along with expedited and synchronous - variants. - - "rcu_busted": This tests an intentionally incorrect version - of RCU in order to help test rcutorture itself. - - "srcu": srcu_read_lock(), srcu_read_unlock() and - call_srcu(), along with expedited and - synchronous variants. - - "sched": preempt_disable(), preempt_enable(), and - call_rcu_sched(), along with expedited, - synchronous, and polling variants. - - "tasks": voluntary context switch and call_rcu_tasks(), - along with expedited and synchronous variants. - - Defaults to "rcu". - -verbose Enable debug printk()s. Default is disabled. - +Module parameters are prefixed by "rcutorture." in +Documentation/admin-guide/kernel-parameters.txt. OUTPUT diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index 4a6854318b17..1ace20815bb1 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -302,7 +302,7 @@ rcu_dereference() must prohibit. The rcu_dereference_protected() variant takes a lockdep expression to indicate which locks must be acquired by the caller. If the indicated protection is not provided, - a lockdep splat is emitted. See RCU/Design/Requirements.html + a lockdep splat is emitted. See RCU/Design/Requirements/Requirements.html and the API's code comments for more details and example usage. The following diagram shows how each API communicates among the @@ -560,7 +560,7 @@ presents two such "toy" implementations of RCU, one that is implemented in terms of familiar locking primitives, and another that more closely resembles "classic" RCU. Both are way too simple for real-world use, lacking both functionality and performance. However, they are useful -in getting a feel for how RCU works. See kernel/rcupdate.c for a +in getting a feel for how RCU works. See kernel/rcu/update.c for a production-quality implementation, and see: http://www.rdrop.com/users/paulmck/RCU |
