[PATCH tip/core/rcu 4/8] docs: Fix typos and drop/fix dead links in RCU documentation

From: paulmck
Date: Tue Jan 05 2021 - 19:55:17 EST

From: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>

It appears the Compaq link moved to a machine at HP for a while
after the merger of the two, but that doesn't work either. A search
of HP for "wiz_2637" (w and w/o html suffix) comes up empty.

Since the references aren't critical to the documents we remove them.

Also, the lkml.kernel.org/g links have been broken for ages, so replace
them with lore.kernel.org/r links - standardize on lore for all links too.

Note that we put off fixing these 4y ago - presumably thinking that a
treewide fixup was pending. Probably safe to go fix the RCU ones now.


Cc: Michael Opdenacker <michael.opdenacker@xxxxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
.../RCU/Design/Requirements/Requirements.rst | 23 +++++++++++-----------
Documentation/RCU/checklist.rst | 8 +++-----
2 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst
index 1e3df77..f32f8fa 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.rst
+++ b/Documentation/RCU/Design/Requirements/Requirements.rst
@@ -321,11 +321,10 @@ do_something_gp_buggy() below:
12 }

However, this temptation must be resisted because there are a
-surprisingly large number of ways that the compiler (to say nothing of
-`DEC Alpha CPUs <https://h71000.www7.hp.com/wizard/wiz_2637.html>`__)
-can trip this code up. For but one example, if the compiler were short
-of registers, it might choose to refetch from ``gp`` rather than keeping
-a separate copy in ``p`` as follows:
+surprisingly large number of ways that the compiler (or weak ordering
+CPUs like the DEC Alpha) can trip this code up. For but one example, if
+the compiler were short of registers, it might choose to refetch from
+``gp`` rather than keeping a separate copy in ``p`` as follows:


@@ -1183,7 +1182,7 @@ costs have plummeted. However, as I learned from Matt Mackall's
`bloatwatch <http://elinux.org/Linux_Tiny-FAQ>`__ efforts, memory
footprint is critically important on single-CPU systems with
non-preemptible (``CONFIG_PREEMPT=n``) kernels, and thus `tiny
-RCU <https://lkml.kernel.org/g/20090113221724.GA15307@xxxxxxxxxxxxxxxxxx>`__
+RCU <https://lore.kernel.org/r/20090113221724.GA15307@xxxxxxxxxxxxxxxxxx>`__
was born. Josh Triplett has since taken over the small-memory banner
with his `Linux kernel tinification <https://tiny.wiki.kernel.org/>`__
project, which resulted in `SRCU <#Sleepable%20RCU>`__ becoming optional
@@ -1624,7 +1623,7 @@ against mishaps and misuse:
init_rcu_head() and cleaned up with destroy_rcu_head().
Mathieu Desnoyers made me aware of this requirement, and also
supplied the needed
- `patch <https://lkml.kernel.org/g/20100319013024.GA28456@Krystal>`__.
+ `patch <https://lore.kernel.org/r/20100319013024.GA28456@Krystal>`__.
#. An infinite loop in an RCU read-side critical section will eventually
trigger an RCU CPU stall warning splat, with the duration of
“eventually” being controlled by the ``RCU_CPU_STALL_TIMEOUT``
@@ -1716,7 +1715,7 @@ requires almost all of them be hidden behind a ``CONFIG_RCU_EXPERT``

This all should be quite obvious, but the fact remains that Linus
Torvalds recently had to
-`remind <https://lkml.kernel.org/g/CA+55aFy4wcCwaL4okTs8wXhGZ5h-ibecy_Meg9C4MNQrUnwMcg@xxxxxxxxxxxxxx>`__
+`remind <https://lore.kernel.org/r/CA+55aFy4wcCwaL4okTs8wXhGZ5h-ibecy_Meg9C4MNQrUnwMcg@xxxxxxxxxxxxxx>`__
me of this requirement.

Firmware Interface
@@ -1837,9 +1836,9 @@ NMI handlers.

The name notwithstanding, some Linux-kernel architectures can have
nested NMIs, which RCU must handle correctly. Andy Lutomirski `surprised
-me <https://lkml.kernel.org/r/CALCETrXLq1y7e_dKFPgou-FKHB6Pu-r8+t-6Ds+8=va7anBWDA@xxxxxxxxxxxxxx>`__
+me <https://lore.kernel.org/r/CALCETrXLq1y7e_dKFPgou-FKHB6Pu-r8+t-6Ds+8=va7anBWDA@xxxxxxxxxxxxxx>`__
with this requirement; he also kindly surprised me with `an
-algorithm <https://lkml.kernel.org/r/CALCETrXSY9JpW3uE6H8WYk81sg56qasA2aqmjMPsq5dOtzso=g@xxxxxxxxxxxxxx>`__
+algorithm <https://lore.kernel.org/r/CALCETrXSY9JpW3uE6H8WYk81sg56qasA2aqmjMPsq5dOtzso=g@xxxxxxxxxxxxxx>`__
that meets this requirement.

Furthermore, NMI handlers can be interrupted by what appear to RCU to be
@@ -2264,7 +2263,7 @@ more extreme measures. Returning to the ``page`` structure, the
``rcu_head`` field shares storage with a great many other structures
that are used at various points in the corresponding page's lifetime. In
order to correctly resolve certain `race
-conditions <https://lkml.kernel.org/g/1439976106-137226-1-git-send-email-kirill.shutemov@xxxxxxxxxxxxxxx>`__,
+conditions <https://lore.kernel.org/r/1439976106-137226-1-git-send-email-kirill.shutemov@xxxxxxxxxxxxxxx>`__,
the Linux kernel's memory-management subsystem needs a particular bit to
remain zero during all phases of grace-period processing, and that bit
happens to map to the bottom bit of the ``rcu_head`` structure's
@@ -2328,7 +2327,7 @@ preempted. This requirement made its presence known after users made it
clear that an earlier `real-time
patch <https://lwn.net/Articles/107930/>`__ did not meet their needs, in
conjunction with some `RCU
-issues <https://lkml.kernel.org/g/20050318002026.GA2693@xxxxxxxxxx>`__
+issues <https://lore.kernel.org/r/20050318002026.GA2693@xxxxxxxxxx>`__
encountered by a very early version of the -rt patchset.

In addition, RCU must make do with a sub-100-microsecond real-time
diff --git a/Documentation/RCU/checklist.rst b/Documentation/RCU/checklist.rst
index bb7128e..2d1dc1d 100644
--- a/Documentation/RCU/checklist.rst
+++ b/Documentation/RCU/checklist.rst
@@ -70,7 +70,7 @@ over a rather long period of time, but improvements are always welcome!
is less readable and prevents lockdep from detecting locking issues.

Letting RCU-protected pointers "leak" out of an RCU read-side
- critical section is every bid as bad as letting them leak out
+ critical section is every bit as bad as letting them leak out
from under a lock. Unless, of course, you have arranged some
other means of protection, such as a lock or a reference count
-before- letting them out of the RCU read-side critical section.
@@ -129,9 +129,7 @@ over a rather long period of time, but improvements are always welcome!
accesses. The rcu_dereference() primitive ensures that
the CPU picks up the pointer before it picks up the data
that the pointer points to. This really is necessary
- on Alpha CPUs. If you don't believe me, see:
- http://www.openvms.compaq.com/wizard/wiz_2637.html
+ on Alpha CPUs.

The rcu_dereference() primitive is also an excellent
documentation aid, letting the person reading the
@@ -216,7 +214,7 @@ over a rather long period of time, but improvements are always welcome!
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(),
- then the corresponding readers my use rcu_read_lock() and
+ then the corresponding readers may 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,
for example, rcu_read_lock_sched() and rcu_read_unlock_sched().