On Tue, Oct 15, 2019 at 09:18:13PM +0200, Sebastian Andrzej Siewior wrote: > The config option `CONFIG_PREEMPT' is used for the preemption model > "Low-Latency Desktop". The config option `CONFIG_PREEMPTION' is enabled > when kernel preemption is enabled which is true for the `CONFIG_PREEMPT' > and `CONFIG_PREEMPT_RT' preemption models. > > Use `CONFIG_PREEMPTION' if it applies to both preemption models and not > just to `CONFIG_PREEMPT'. > > Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> > Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> > Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> > Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> > Cc: linux-doc@xxxxxxxxxxxxxxx > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Sadly, this one ran afoul of the .txt-to-.rst migration. Even applying it against linus/master and cherry-picking it does not help. I will defer it for the moment -- perhaps Mauro or Joel have some advice. Thanx, Paul > --- > .../Expedited-Grace-Periods.html | 8 +++---- > .../RCU/Design/Requirements/Requirements.html | 24 +++++++++---------- > Documentation/RCU/checklist.txt | 4 ++-- > Documentation/RCU/rcubarrier.txt | 8 +++---- > Documentation/RCU/stallwarn.txt | 4 ++-- > Documentation/RCU/whatisRCU.txt | 7 +++--- > 6 files changed, 28 insertions(+), 27 deletions(-) > > 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 57300db4b5ff6..31c99382994e0 100644 > --- a/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html > +++ b/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html > @@ -56,8 +56,8 @@ sections. > RCU-preempt Expedited Grace Periods</a></h2> > > <p> > -<tt>CONFIG_PREEMPT=y</tt> kernels implement RCU-preempt. > -The overall flow of the handling of a given CPU by an RCU-preempt > +<tt>CONFIG_PREEMPT=y</tt> and <tt>CONFIG_PREEMPT_RT=y</tt> kernels implement > +RCU-preempt. The overall flow of the handling of a given CPU by an RCU-preempt > expedited grace period is shown in the following diagram: > > <p><img src="ExpRCUFlow.svg" alt="ExpRCUFlow.svg" width="55%"> > @@ -140,8 +140,8 @@ or offline, among other things. > RCU-sched Expedited Grace Periods</a></h2> > > <p> > -<tt>CONFIG_PREEMPT=n</tt> kernels implement RCU-sched. > -The overall flow of the handling of a given CPU by an RCU-sched > +<tt>CONFIG_PREEMPT=n</tt> and <tt>CONFIG_PREEMPT_RT=n</tt> kernels implement > +RCU-sched. The overall flow of the handling of a given CPU by an RCU-sched > expedited grace period is shown in the following diagram: > > <p><img src="ExpSchedFlow.svg" alt="ExpSchedFlow.svg" width="55%"> > diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html > index 467251f7fef69..348c5db1ff2bb 100644 > --- a/Documentation/RCU/Design/Requirements/Requirements.html > +++ b/Documentation/RCU/Design/Requirements/Requirements.html > @@ -106,7 +106,7 @@ big RCU read-side critical section. > Production-quality implementations of <tt>rcu_read_lock()</tt> and > <tt>rcu_read_unlock()</tt> are extremely lightweight, and in > fact have exactly zero overhead in Linux kernels built for production > -use with <tt>CONFIG_PREEMPT=n</tt>. > +use with <tt>CONFIG_PREEMPTION=n</tt>. > > <p> > This guarantee allows ordering to be enforced with extremely low > @@ -1499,7 +1499,7 @@ costs have plummeted. > However, as I learned from Matt Mackall's > <a href="http://elinux.org/Linux_Tiny-FAQ";>bloatwatch</a> > efforts, memory footprint is critically important on single-CPU systems with > -non-preemptible (<tt>CONFIG_PREEMPT=n</tt>) kernels, and thus > +non-preemptible (<tt>CONFIG_PREEMPTION=n</tt>) kernels, and thus > <a href="https://lkml.kernel.org/g/20090113221724.GA15307@xxxxxxxxxxxxxxxxxx";>tiny RCU</a> > was born. > Josh Triplett has since taken over the small-memory banner with his > @@ -1887,7 +1887,7 @@ constructs, there are limitations. > <p> > Implementations of RCU for which <tt>rcu_read_lock()</tt> > and <tt>rcu_read_unlock()</tt> generate no code, such as > -Linux-kernel RCU when <tt>CONFIG_PREEMPT=n</tt>, can be > +Linux-kernel RCU when <tt>CONFIG_PREEMPTION=n</tt>, can be > nested arbitrarily deeply. > After all, there is no overhead. > Except that if all these instances of <tt>rcu_read_lock()</tt> > @@ -2229,7 +2229,7 @@ be a no-op. > <p> > However, once the scheduler has spawned its first kthread, this early > boot trick fails for <tt>synchronize_rcu()</tt> (as well as for > -<tt>synchronize_rcu_expedited()</tt>) in <tt>CONFIG_PREEMPT=y</tt> > +<tt>synchronize_rcu_expedited()</tt>) in <tt>CONFIG_PREEMPTION=y</tt> > kernels. > The reason is that an RCU read-side critical section might be preempted, > which means that a subsequent <tt>synchronize_rcu()</tt> really does have > @@ -2568,7 +2568,7 @@ The compiler must not be permitted to transform this source code into > > <p> > If the compiler did make this transformation in a > -<tt>CONFIG_PREEMPT=n</tt> kernel build, and if <tt>get_user()</tt> did > +<tt>CONFIG_PREEMPTION=n</tt> kernel build, and if <tt>get_user()</tt> did > page fault, the result would be a quiescent state in the middle > of an RCU read-side critical section. > This misplaced quiescent state could result in line 4 being > @@ -2906,7 +2906,7 @@ in conjunction with the > The real-time-latency response requirements are such that the > traditional approach of disabling preemption across RCU > read-side critical sections is inappropriate. > -Kernels built with <tt>CONFIG_PREEMPT=y</tt> therefore > +Kernels built with <tt>CONFIG_PREEMPTION=y</tt> therefore > use an RCU implementation that allows RCU read-side critical > sections to be preempted. > This requirement made its presence known after users made it > @@ -3064,7 +3064,7 @@ includes > <tt>rcu_barrier_bh()</tt>, and > <tt>rcu_read_lock_bh_held()</tt>. > However, the update-side APIs are now simple wrappers for other RCU > -flavors, namely RCU-sched in CONFIG_PREEMPT=n kernels and RCU-preempt > +flavors, namely RCU-sched in CONFIG_PREEMPTION=n kernels and RCU-preempt > otherwise. > > <h3><a name="Sched Flavor">Sched Flavor (Historical)</a></h3> > @@ -3088,12 +3088,12 @@ of an RCU read-side critical section can be a quiescent state. > Therefore, <i>RCU-sched</i> was created, which follows “classic” > RCU in that an RCU-sched grace period waits for for pre-existing > interrupt and NMI handlers. > -In kernels built with <tt>CONFIG_PREEMPT=n</tt>, the RCU and RCU-sched > +In kernels built with <tt>CONFIG_PREEMPTION=n</tt>, the RCU and RCU-sched > APIs have identical implementations, while kernels built with > -<tt>CONFIG_PREEMPT=y</tt> provide a separate implementation for each. > +<tt>CONFIG_PREEMPTION=y</tt> provide a separate implementation for each. > > <p> > -Note well that in <tt>CONFIG_PREEMPT=y</tt> kernels, > +Note well that in <tt>CONFIG_PREEMPTION=y</tt> kernels, > <tt>rcu_read_lock_sched()</tt> and <tt>rcu_read_unlock_sched()</tt> > disable and re-enable preemption, respectively. > This means that if there was a preemption attempt during the > @@ -3302,12 +3302,12 @@ The tasks-RCU API is quite compact, consisting only of > <tt>call_rcu_tasks()</tt>, > <tt>synchronize_rcu_tasks()</tt>, and > <tt>rcu_barrier_tasks()</tt>. > -In <tt>CONFIG_PREEMPT=n</tt> kernels, trampolines cannot be preempted, > +In <tt>CONFIG_PREEMPTION=n</tt> kernels, trampolines cannot be preempted, > so these APIs map to > <tt>call_rcu()</tt>, > <tt>synchronize_rcu()</tt>, and > <tt>rcu_barrier()</tt>, respectively. > -In <tt>CONFIG_PREEMPT=y</tt> kernels, trampolines can be preempted, > +In <tt>CONFIG_PREEMPTION=y</tt> kernels, trampolines can be preempted, > and these three APIs are therefore implemented by separate functions > that check for voluntary context switches. > > diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt > index e98ff261a438b..087dc6c22c37c 100644 > --- a/Documentation/RCU/checklist.txt > +++ b/Documentation/RCU/checklist.txt > @@ -210,8 +210,8 @@ over a rather long period of time, but improvements are always welcome! > the rest of the system. > > 7. As of v4.20, a given kernel implements only one RCU flavor, > - which is RCU-sched for PREEMPT=n and RCU-preempt for PREEMPT=y. > - If the updater uses call_rcu() or synchronize_rcu(), > + which is RCU-sched for PREEMPTION=n and RCU-preempt for > + PREEMPTION=y. If the updater uses call_rcu() or synchronize_rcu(), > then the corresponding readers my use rcu_read_lock() and > rcu_read_unlock(), rcu_read_lock_bh() and rcu_read_unlock_bh(), > or any pair of primitives that disables and re-enables preemption, > diff --git a/Documentation/RCU/rcubarrier.txt b/Documentation/RCU/rcubarrier.txt > index a2782df697328..5aa93c215af46 100644 > --- a/Documentation/RCU/rcubarrier.txt > +++ b/Documentation/RCU/rcubarrier.txt > @@ -6,8 +6,8 @@ RCU (read-copy update) is a synchronization mechanism that can be thought > of as a replacement for read-writer locking (among other things), but with > very low-overhead readers that are immune to deadlock, priority inversion, > and unbounded latency. RCU read-side critical sections are delimited > -by rcu_read_lock() and rcu_read_unlock(), which, in non-CONFIG_PREEMPT > -kernels, generate no code whatsoever. > +by rcu_read_lock() and rcu_read_unlock(), which, in > +non-CONFIG_PREEMPTION kernels, generate no code whatsoever. > > This means that RCU writers are unaware of the presence of concurrent > readers, so that RCU updates to shared data must be undertaken quite > @@ -303,10 +303,10 @@ Answer: This cannot happen. The reason is that on_each_cpu() has its last > to smp_call_function() and further to smp_call_function_on_cpu(), > causing this latter to spin until the cross-CPU invocation of > rcu_barrier_func() has completed. This by itself would prevent > - a grace period from completing on non-CONFIG_PREEMPT kernels, > + a grace period from completing on non-CONFIG_PREEMPTION kernels, > since each CPU must undergo a context switch (or other quiescent > state) before the grace period can complete. However, this is > - of no use in CONFIG_PREEMPT kernels. > + of no use in CONFIG_PREEMPTION kernels. > > Therefore, on_each_cpu() disables preemption across its call > to smp_call_function() and also across the local call to > diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt > index f48f4621ccbc2..bd510771b75ec 100644 > --- a/Documentation/RCU/stallwarn.txt > +++ b/Documentation/RCU/stallwarn.txt > @@ -20,7 +20,7 @@ o A CPU looping with preemption disabled. > > o A CPU looping with bottom halves disabled. > > -o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel > +o For !CONFIG_PREEMPTION kernels, a CPU looping anywhere in the kernel > without invoking schedule(). If the looping in the kernel is > really expected and desirable behavior, you might need to add > some calls to cond_resched(). > @@ -39,7 +39,7 @@ o Anything that prevents RCU's grace-period kthreads from running. > result in the "rcu_.*kthread starved for" console-log message, > which will include additional debugging information. > > -o A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might > +o A CPU-bound real-time task in a CONFIG_PREEMPTION kernel, which might > happen to preempt a low-priority task in the middle of an RCU > read-side critical section. This is especially damaging if > that low-priority task is not permitted to run on any other CPU, > diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt > index 7e1a8721637ab..7e03e8f80b293 100644 > --- a/Documentation/RCU/whatisRCU.txt > +++ b/Documentation/RCU/whatisRCU.txt > @@ -648,9 +648,10 @@ Quick Quiz #1: Why is this argument naive? How could a deadlock > > This section presents a "toy" RCU implementation that is based on > "classic RCU". It is also short on performance (but only for updates) and > -on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT > -kernels. The definitions of rcu_dereference() and rcu_assign_pointer() > -are the same as those shown in the preceding section, so they are omitted. > +on features such as hotplug CPU and the ability to run in > +CONFIG_PREEMPTION kernels. The definitions of rcu_dereference() and > +rcu_assign_pointer() are the same as those shown in the preceding > +section, so they are omitted. > > void rcu_read_lock(void) { } > > -- > 2.23.0 >
