linux-kernel - [PATCH] srcu: Priority check rcu_gp_is_expedited() in synchronize

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-next>] [day] [month] [year] [list]

Message-Id: <20230704070809.31951-1-qiang.zhang1211@gmail.com>
Date:   Tue,  4 Jul 2023 15:08:09 +0800
From:   Zqiang <qiang.zhang1211@...il.com>
To:     paulmck@...nel.org, frederic@...nel.org, quic_neeraju@...cinc.com,
        joel@...lfernandes.org, qiang.zhang1211@...il.com
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] srcu: Priority check rcu_gp_is_expedited() in synchronize_srcu()

Since the atomic variable rcu_expedited_nesting is initialized to
true, so the rcu_gp_is_expedited() is always return true during
system startup until the rcu_end_inkernel_boot() is called. this
means that without setting rcupdate.rcu_normal=1 and before the
rcu_end_inkernel_boot() is executed, regardless of whether the
return value of srcu_might_be_idle() is true, call synchronize_srcu()
always fall back to synchronize_srcu_expedited(), so there is
no need to checking srcu_might_be_idle() return value.

For the rcupdate.rcu_normal=0, rcupdate.rcu_normal_after_boot=0 and
rcupdate.rcu_expedited=1 kernels, there is also no need to checking
srcu_might_be_idle() return value.

This commit therefore priority check rcu_gp_is_expedited() return value
in synchronize_srcu().

Signed-off-by: Zqiang <qiang.zhang1211@...il.com>
---
 kernel/rcu/srcutree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 20d7a238d675..a819f11d9b90 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1435,7 +1435,7 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
  */
 void synchronize_srcu(struct srcu_struct *ssp)
 {
-	if (srcu_might_be_idle(ssp) || rcu_gp_is_expedited())
+	if (rcu_gp_is_expedited() || srcu_might_be_idle(ssp))
 		synchronize_srcu_expedited(ssp);
 	else
 		__synchronize_srcu(ssp, true);
-- 
2.17.1