linux-kernel - [tip: sched/core] lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 19 May 2021 08:09:06 -0000
From:   "tip-bot2 for Yejune Deng" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Valentin Schneider <valentin.schneider@....com>,
        Yejune Deng <yejune.deng@...il.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] lib/smp_processor_id: Use is_percpu_thread()
 instead of nr_cpus_allowed

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     0019699518cc026b5bd912425be8e424843d5b33
Gitweb:        https://git.kernel.org/tip/0019699518cc026b5bd912425be8e424843d5b33
Author:        Yejune Deng <yejune.deng@...il.com>
AuthorDate:    Mon, 10 May 2021 16:10:24 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 18 May 2021 12:53:54 +02:00

lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus_allowed

is_percpu_thread() more elegantly handles SMP vs UP, and further checks the
presence of PF_NO_SETAFFINITY. This lets us catch cases where
check_preemption_disabled() can race with a concurrent sched_setaffinity().

[Amended changelog]
Signed-off-by: Valentin Schneider <valentin.schneider@....com>
Signed-off-by: Yejune Deng <yejune.deng@...il.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20210510151024.2448573-3-valentin.schneider@arm.com
---
 lib/smp_processor_id.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/lib/smp_processor_id.c b/lib/smp_processor_id.c
index 1c1dbd3..046ac62 100644
--- a/lib/smp_processor_id.c
+++ b/lib/smp_processor_id.c
@@ -19,11 +19,7 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2)
 	if (irqs_disabled())
 		goto out;
 
-	/*
-	 * Kernel threads bound to a single CPU can safely use
-	 * smp_processor_id():
-	 */
-	if (current->nr_cpus_allowed == 1)
+	if (is_percpu_thread())
 		goto out;
 
 #ifdef CONFIG_SMP