From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Qian Cai <cai@redhat.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>
Subject: [PATCH 5.9 11/14] powerpc/smp: Call rcu_cpu_starting() earlier
Date: Fri, 20 Nov 2020 12:03:49 +0100 [thread overview]
Message-ID: <20201120104541.719427713@linuxfoundation.org> (raw)
In-Reply-To: <20201120104541.168007611@linuxfoundation.org>
From: Qian Cai <cai@redhat.com>
commit 99f070b62322a4b8c1252952735806d09eb44b68 upstream.
The call to rcu_cpu_starting() in start_secondary() is not early
enough in the CPU-hotplug onlining process, which results in lockdep
splats as follows (with CONFIG_PROVE_RCU_LIST=y):
WARNING: suspicious RCU usage
-----------------------------
kernel/locking/lockdep.c:3497 RCU-list traversed in non-reader section!!
other info that might help us debug this:
RCU used illegally from offline CPU!
rcu_scheduler_active = 1, debug_locks = 1
no locks held by swapper/1/0.
Call Trace:
dump_stack+0xec/0x144 (unreliable)
lockdep_rcu_suspicious+0x128/0x14c
__lock_acquire+0x1060/0x1c60
lock_acquire+0x140/0x5f0
_raw_spin_lock_irqsave+0x64/0xb0
clockevents_register_device+0x74/0x270
register_decrementer_clockevent+0x94/0x110
start_secondary+0x134/0x800
start_secondary_prolog+0x10/0x14
This is avoided by adding a call to rcu_cpu_starting() near the
beginning of the start_secondary() function. Note that the
raw_smp_processor_id() is required in order to avoid calling into
lockdep before RCU has declared the CPU to be watched for readers.
It's safe to call rcu_cpu_starting() in the arch code as well as later
in generic code, as explained by Paul:
It uses a per-CPU variable so that RCU pays attention only to the
first call to rcu_cpu_starting() if there is more than one of them.
This is even intentional, due to there being a generic
arch-independent call to rcu_cpu_starting() in
notify_cpu_starting().
So multiple calls to rcu_cpu_starting() are fine by design.
Fixes: 4d004099a668 ("lockdep: Fix lockdep recursion")
Signed-off-by: Qian Cai <cai@redhat.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
[mpe: Add Fixes tag, reword slightly & expand change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201028182334.13466-1-cai@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/kernel/smp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -1251,7 +1251,7 @@ static bool shared_caches;
/* Activate a secondary processor. */
void start_secondary(void *unused)
{
- unsigned int cpu = smp_processor_id();
+ unsigned int cpu = raw_smp_processor_id();
struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
mmgrab(&init_mm);
next prev parent reply other threads:[~2020-11-20 11:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-20 11:03 [PATCH 5.9 00/14] 5.9.10-rc1 review Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 01/14] selftests/powerpc: rfi_flush: disable entry flush if present Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 02/14] powerpc/64s: flush L1D on kernel entry Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 03/14] powerpc/64s: flush L1D after user accesses Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 04/14] powerpc: Only include kup-radix.h for 64-bit Book3S Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 05/14] selftests/powerpc: entry flush test Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 06/14] leds: lm3697: Fix out-of-bound access Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 07/14] Input: sunkbd - avoid use-after-free in teardown paths Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 08/14] mac80211: always wind down STA state Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 09/14] can: proc: can_remove_proc(): silence remove_proc_entry warning Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 10/14] selftests/harness: prettify SKIP message whitespace again Greg Kroah-Hartman
2020-11-20 11:03 ` Greg Kroah-Hartman [this message]
2020-11-20 11:03 ` [PATCH 5.9 12/14] perf/x86/intel/uncore: Fix Add BW copypasta Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 13/14] KVM: x86: clflushopt should be treated as a no-op by emulation Greg Kroah-Hartman
2020-11-20 11:03 ` [PATCH 5.9 14/14] ACPI: GED: fix -Wformat Greg Kroah-Hartman
2020-11-20 17:52 ` [PATCH 5.9 00/14] 5.9.10-rc1 review Jeffrin Jose T
2020-11-20 22:27 ` Shuah Khan
2020-11-22 9:18 ` Greg Kroah-Hartman
2020-11-21 11:12 ` Naresh Kamboju
2020-11-22 9:18 ` Greg Kroah-Hartman
[not found] ` <20201121183817.GG111877@roeck-us.net>
2020-11-22 9:19 ` Greg Kroah-Hartman
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