linux-kernel - Re: [PATCH v3 1/4] rcutorture: Don't disable softirqs with preemption disabled when PREEMPT

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]

Message-ID: <20210817131741.evduh4fw7vyv2dzt@linutronix.de>
Date:   Tue, 17 Aug 2021 15:17:41 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        rcu@...r.kernel.org, linux-rt-users@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Steven Price <steven.price@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Mike Galbraith <efault@....de>
Subject: Re: [PATCH v3 1/4] rcutorture: Don't disable softirqs with
 preemption disabled when PREEMPT_RT

On 2021-08-17 14:13:47 [+0200], To Valentin Schneider wrote:
> > index eecd1caef71d..4f3db1d3170d 100644
> > --- a/kernel/rcu/rcutorture.c
> > +++ b/kernel/rcu/rcutorture.c
> > @@ -1548,6 +1548,8 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
> >  	 * them on non-RT.
> >  	 */
> >  	if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
> > +		/* Can't disable bh in atomic context under PREEMPT_RT */
> > +		mask &= ~(RCUTORTURE_RDR_ATOM_BH | RCUTORTURE_RDR_ATOM_RBH);
> 
> Let me stare at this…

I would fold this

--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1549,6 +1549,13 @@ rcutorture_extend_mask(int oldmask, stru
 	 */
 	if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
 		/*
+		 * Can't disable bh in atomic context if bh was already
+		 * disabled by another task on the same CPU. Instead of
+		 * attempting to track this, just avoid disabling bh in atomic
+		 * context.
+		 */
+		mask &= ~atomic_bhs;
+		/*
 		 * Can't release the outermost rcu lock in an irq disabled
 		 * section without preemption also being disabled, if irqs
 		 * had ever been enabled during this RCU critical section
@@ -1559,16 +1566,6 @@ rcutorture_extend_mask(int oldmask, stru
 		    !(mask & preempts))
 			mask |= RCUTORTURE_RDR_RCU;
 
-		/* Can't modify atomic bh in non-atomic context */
-		if ((oldmask & atomic_bhs) && (mask & atomic_bhs) &&
-		    !(mask & preempts_irq)) {
-			mask |= oldmask & preempts_irq;
-			if (mask & RCUTORTURE_RDR_IRQ)
-				mask |= oldmask & tmp;
-		}
-		if ((mask & atomic_bhs) && !(mask & preempts_irq))
-			mask |= RCUTORTURE_RDR_PREEMPT;
-
 		/* Can't modify non-atomic bh in atomic context */
 		tmp = nonatomic_bhs;
 		if (oldmask & preempts_irq)

into the original patch and forward it upstream…

Sebastian