Re: [PATCH] mips/smp: Call rcu_cpu_starting() earlier

[Florian Fainelli]

On 1/19/2024 10:38 PM, Greg Kroah-Hartman wrote:
> On Fri, Jan 19, 2024 at 05:38:11PM +0100, Stefan Wiehler wrote:
> > rcu_cpu_starting() must be called before clockevents_register_device() to avoid
> > the following lockdep splat triggered by calling list_add() when
> > CONFIG_PROVE_RCU_LIST=y:
> >
> >    WARNING: suspicious RCU usage
> >    ...
> >    -----------------------------
> >    kernel/locking/lockdep.c:3680 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:
> >    [<ffffffff8012a434>] show_stack+0x64/0x158
> >    [<ffffffff80a93d98>] dump_stack_lvl+0x90/0xc4
> >    [<ffffffff801c9e9c>] __lock_acquire+0x1404/0x2940
> >    [<ffffffff801cbf3c>] lock_acquire+0x14c/0x448
> >    [<ffffffff80aa4260>] _raw_spin_lock_irqsave+0x50/0x88
> >    [<ffffffff8021e0c8>] clockevents_register_device+0x60/0x1e8
> >    [<ffffffff80130ff0>] r4k_clockevent_init+0x220/0x3a0
> >    [<ffffffff801339d0>] start_secondary+0x50/0x3b8
> >
> > raw_smp_processor_id() is required in order to avoid calling into lockdep
> > before RCU has declared the CPU to be watched for readers.
> >
> > See also commit 29368e093921 ("x86/smpboot:  Move rcu_cpu_starting() earlier"),
> > commit de5d9dae150c ("s390/smp: move rcu_cpu_starting() earlier") and commit
> > 99f070b62322 ("powerpc/smp: Call rcu_cpu_starting() earlier").
> >
> > Signed-off-by: Stefan Wiehler <stefan.wiehler@xxxxxxxxx>
> > Reviewed-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> > Signed-off-by: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> > ---
> >   arch/mips/kernel/smp.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
>
> What is the git commit id of this change in Linus's tree?  What
> kernel(s) should this be applied to?

The upstream commit is 55702ec9603ebeffb15e6f7b113623fe1d8872f4 
("mips/smp: Call rcutree_report_cpu_starting() earlier") and this change 
from Stefan should be applied to both the 6.1 stable and 6.6 stable 
branches. Thanks!
--
Florian