Messages in this thread | | | From | Wander Lairson Costa <> | Date | Thu, 1 Jun 2023 14:45:53 -0300 | Subject | Re: [PATCH v9] kernel/fork: beware of __put_task_struct calling context |
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On Mon, May 29, 2023 at 9:23 AM Oleg Nesterov <oleg@redhat.com> wrote: > > On 05/17, Wander Lairson Costa wrote: > > > > On Wed, May 17, 2023 at 12:26 PM Oleg Nesterov <oleg@redhat.com> wrote: > > > > > > LGTM but we still need to understand the possible problems with CONFIG_PROVE_RAW_LOCK_NESTING ... > > > > > > Again, I'll try to investigate when I have time although I am not sure I can really help. > > > > > > Perhaps you too can try to do this ? ;) > > > > > > > FWIW, I tested this patch with CONFIG_PROVE_LOCK_NESTING in RT and > > stock kernels. No splat happened. > > Strange... FYI, I am running the kernel with this patch > > diff --git a/kernel/sys.c b/kernel/sys.c > index 339fee3eff6a..3169cceddf3b 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -2412,6 +2412,17 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, > > error = 0; > switch (option) { > + case 666: { > + static DEFINE_SPINLOCK(l); > + static DEFINE_RAW_SPINLOCK(r); > + > + raw_spin_lock(&r); > + spin_lock(&l); > + spin_unlock(&l); > + raw_spin_unlock(&r); > + > + break; > + } > case PR_SET_PDEATHSIG: > if (!valid_signal(arg2)) { > error = -EINVAL; > > applied (because I am too lazy to compile a module ;) and >
FWIW, I converted it to a module [1]
> # perl -e 'syscall 157,666' > > triggers the lockdep bug > > ============================= > [ BUG: Invalid wait context ] > 6.4.0-rc2-00018-g4d6d4c7f541d-dirty #1176 Not tainted > ----------------------------- > perl/35 is trying to lock: > ffffffff81c4cc18 (l){....}-{3:3}, at: __do_sys_prctl+0x21b/0x87b > other info that might help us debug this: > context-{5:5} > ... > > as expected. >
Yeah, I tried it here and I had the same results, but only in the RT kernel. But running the reproducer for put_task_struct(), works fine.
> Looks like your testing was wrong... Or maybe you missed another lockdep problem ? > Did you check dmesg? Perhaps lockdep detected another bug,say, even at boot time ? > In this case debug_locks_off() sets debug_locks = 0 and this disables lockdep. > > Oleg. >
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