linux-kernel - [tip:locking/core] jump_label: Sort entries of the same key by the code

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Date:   Mon, 17 Jun 2019 07:14:30 -0700
From:   tip-bot for Daniel Bristot de Oliveira <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     rostedt@...dmis.org, mhiramat@...nel.org, tglx@...utronix.de,
        crecklin@...hat.com, gregkh@...uxfoundation.org, jbaron@...mai.com,
        bp@...en8.de, peterz@...radead.org, jkosina@...e.cz,
        linux-kernel@...r.kernel.org, mingo@...nel.org,
        mtosatti@...hat.com, torvalds@...ux-foundation.org,
        williams@...hat.com, hpa@...or.com, jpoimboe@...hat.com,
        bristot@...hat.com, swood@...hat.com
Subject: [tip:locking/core] jump_label: Sort entries of the same key by the
 code

Commit-ID:  0f133021bd82548a33580bfb7b055e8857f46c2a
Gitweb:     https://git.kernel.org/tip/0f133021bd82548a33580bfb7b055e8857f46c2a
Author:     Daniel Bristot de Oliveira <bristot@...hat.com>
AuthorDate: Wed, 12 Jun 2019 11:57:28 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 17 Jun 2019 12:09:21 +0200

jump_label: Sort entries of the same key by the code

In the batching mode, all the entries of a given key are updated at once.
During the update of a key, a hit in the int3 handler will check if the
hitting code address belongs to one of these keys.

To optimize the search of a given code in the vector of entries being
updated, a binary search is used. The binary search relies on the order
of the entries of a key by its code. Hence the keys need to be sorted
by the code too, so sort the entries of a given key by the code.

Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Chris von Recklinghausen <crecklin@...hat.com>
Cc: Clark Williams <williams@...hat.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Jason Baron <jbaron@...mai.com>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Scott Wood <swood@...hat.com>
Cc: Steven Rostedt (VMware) <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: https://lkml.kernel.org/r/f57ae83e0592418ba269866bb7ade570fc8632e0.1560325897.git.bristot@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/jump_label.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 24f0d3b1526b..ca00ac10d9b9 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -37,12 +37,26 @@ static int jump_label_cmp(const void *a, const void *b)
 	const struct jump_entry *jea = a;
 	const struct jump_entry *jeb = b;
 
+	/*
+	 * Entrires are sorted by key.
+	 */
 	if (jump_entry_key(jea) < jump_entry_key(jeb))
 		return -1;
 
 	if (jump_entry_key(jea) > jump_entry_key(jeb))
 		return 1;
 
+	/*
+	 * In the batching mode, entries should also be sorted by the code
+	 * inside the already sorted list of entries, enabling a bsearch in
+	 * the vector.
+	 */
+	if (jump_entry_code(jea) < jump_entry_code(jeb))
+		return -1;
+
+	if (jump_entry_code(jea) > jump_entry_code(jeb))
+		return 1;
+
 	return 0;
 }