linux-kernel - [PATCH RFC 5/5] rcu: Remove rcu_dereference_raw

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Date:   Fri, 24 May 2019 19:49:33 -0400
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Ingo Molnar <mingo@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Josh Triplett <josh@...htriplett.org>, kvm-ppc@...r.kernel.org,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-doc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Paul Mackerras <paulus@...abs.org>, rcu@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH RFC 5/5] rcu: Remove rcu_dereference_raw_notrace since no users

The series removes all users of the API and with this patch, the API
itself. Also fix documentation.

Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 Documentation/RCU/Design/Requirements/Requirements.html | 6 +++---
 include/linux/rcupdate.h                                | 9 ---------
 2 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html
index 5a9238a2883c..9727278893e6 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.html
+++ b/Documentation/RCU/Design/Requirements/Requirements.html
@@ -2512,9 +2512,9 @@ disabled across the entire RCU read-side critical section.
 <p>
 It is possible to use tracing on RCU code, but tracing itself
 uses RCU.
-For this reason, <tt>rcu_dereference_raw_notrace()</tt>
-is provided for use by tracing, which avoids the destructive
-recursion that could otherwise ensue.
+This is the other reason for using, <tt>rcu_dereference_raw()</tt>,
+for use by tracing, which avoids the destructive recursion that could
+otherwise ensue.
 This API is also used by virtualization in some architectures,
 where RCU readers execute in environments in which tracing
 cannot be used.
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 922bb6848813..f917a27fc115 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -472,15 +472,6 @@ static inline void rcu_preempt_sleep_check(void) { }
 	__rcu_dereference_check((p), (c) || rcu_read_lock_sched_held(), \
 				__rcu)
 
-/*
- * The tracing infrastructure traces RCU (we want that), but unfortunately
- * some of the RCU checks causes tracing to lock up the system.
- *
- * The no-tracing version of rcu_dereference_raw() must not call
- * rcu_read_lock_held().
- */
-#define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu)
-
 /**
  * rcu_dereference_protected() - fetch RCU pointer when updates prevented
  * @p: The pointer to read, prior to dereferencing
-- 
2.22.0.rc1.257.g3120a18244-goog