From: Mark Rutland <mark.rutland@arm.com>
To: Yury Norov <ynorov@caviumnetworks.com>
Cc: James Morse <james.morse@arm.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Will Deacon <will.deacon@arm.com>,
Chris Metcalf <cmetcalf@mellanox.com>,
Christopher Lameter <cl@linux.com>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Alexey Klimov <klimov.linux@gmail.com>,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/5] arm64: entry: isb in el1_irq
Date: Fri, 6 Apr 2018 18:50:27 +0100 [thread overview]
Message-ID: <20180406175027.oxaru6r3zptct7vb@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <20180406172211.r42reit2bnpocab2@lakrids.cambridge.arm.com>
On Fri, Apr 06, 2018 at 06:22:11PM +0100, Mark Rutland wrote:
> Digging a bit, I also thing that our ct_user_exit and ct_user_enter
> usage is on dodgy ground today.
>
> For example, in el0_dbg we call do_debug_exception() *before* calling
> ct_user_exit. Which I believe means we'd use RCU while supposedly in an
> extended quiescent period, which would be bad.
It seems this is the case. I can trigger the following by having GDB
place a SW breakpoint:
[ 51.217947] =============================
[ 51.217953] WARNING: suspicious RCU usage
[ 51.217961] 4.16.0 #4 Not tainted
[ 51.217966] -----------------------------
[ 51.217974] ./include/linux/rcupdate.h:632 rcu_read_lock() used illegally while idle!
[ 51.217980]
[ 51.217980] other info that might help us debug this:
[ 51.217980]
[ 51.217987]
[ 51.217987] RCU used illegally from idle CPU!
[ 51.217987] rcu_scheduler_active = 2, debug_locks = 1
[ 51.217992] RCU used illegally from extended quiescent state!
[ 51.217999] 1 lock held by ls/2412:
[ 51.218004] #0: (rcu_read_lock){....}, at: [<0000000092efbdd5>] brk_handler+0x0/0x198
[ 51.218041]
[ 51.218041] stack backtrace:
[ 51.218049] CPU: 2 PID: 2412 Comm: ls Not tainted 4.16.0 #4
[ 51.218055] Hardware name: ARM Juno development board (r1) (DT)
[ 51.218061] Call trace:
[ 51.218070] dump_backtrace+0x0/0x1c8
[ 51.218078] show_stack+0x14/0x20
[ 51.218087] dump_stack+0xac/0xe4
[ 51.218096] lockdep_rcu_suspicious+0xcc/0x110
[ 51.218103] brk_handler+0x144/0x198
[ 51.218110] do_debug_exception+0x9c/0x190
[ 51.218116] el0_dbg+0x14/0x20
We will need to fix this before we can fiddle with kick_all_cpus_sync().
Thanks,
Mark.
next prev parent reply other threads:[~2018-04-06 17:50 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-05 17:17 [PATCH v2 0/2] smp: don't kick CPUs running idle or nohz_full tasks Yury Norov
2018-04-05 17:17 ` [PATCH 1/5] arm64: entry: isb in el1_irq Yury Norov
2018-04-06 10:02 ` James Morse
2018-04-06 16:54 ` Yury Norov
2018-04-06 17:22 ` Mark Rutland
2018-04-06 17:30 ` James Morse
2018-04-06 17:34 ` Mark Rutland
2018-04-06 17:50 ` Mark Rutland [this message]
2018-04-06 10:57 ` Mark Rutland
2018-04-05 17:17 ` [PATCH 2/5] arm64: entry: introduce restore_syscall_args macro Yury Norov
2018-04-05 17:17 ` [PATCH 3/5] arm64: early ISB at exit from extended quiescent state Yury Norov
2018-04-06 10:06 ` James Morse
2018-04-06 11:07 ` Mark Rutland
2018-04-05 17:17 ` [PATCH 4/5] rcu: arm64: add rcu_dynticks_eqs_exit_sync() Yury Norov
2018-04-05 17:18 ` [PATCH 5/5] smp: Lazy synchronization for EQS CPUs in kick_all_cpus_sync() Yury Norov
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