On Tue, Aug 20, 2024 at 04:43:39PM +0200, Frederic Weisbecker wrote:
> Sorry for the html mail, I only have my phone ...
>
> Le mar. 20 août 2024, 13:07, Z qiang <qiang.zhang1211@xxxxxxxxx> a écrit :
>
> > >
> > > Hello, Frederic,
> > >
> > > I have seen this once on Neeraj's tree with a few commits on top (-rcu
> > > commit 46774278c74f ("rcutorture: Test start-poll primitives with
> > > interrupts disabled"). But only the once so far.
> > >
> > > This is the WARN_ON_ONCE(rcu_segcblist_n_cbs(&rdp->cblist)) in
> > > rcu_nocb_rdp_deoffload().
> > >
> > > Thoughts?
> > >
> >
> > The rcu_segcblist_extract_done_cbs() doesn't reduce the count of
> > rsclp->len,
> > in rcu_do_bacth(). this may cause that after we execute the barrier rcu
> > callback, before decrementing the count of rsclp->len, the rcu_barrier()
> > returns and makes a judgment of rcu_segcblist_n_cbs(&rdp->cblist) in
> > rcu_nocb_rdp_deoffload().
> >
>
> That sounds plausible! You just unlocked my thoughts running in circle
> since yesterday.
>
>
> > maybe can use WARN_ON_ONCE(rcu_segcblist_n_segment_cbs()) instead
> > of WARN_ON_ONCE(rcu_segcblist_n_cbs())
> >
> > Thoughts?
>
> I'll test that once I'm back from vacation the september 2nd. Thanks!
Thank you both!!!
Running -next over last night hit a number of boot-time splats, so I
have no idea if this reproduces nicely. Can't have everything! ;-)
Thanx, Paul
> > Thanks
> > Zqiang
> >
> >
> >
> >
> > > Thanx, Paul
> > >
> > > ------------------------------------------------------------------------
> > >
> > > [18839.499664] ------------[ cut here ]------------
> > > [18839.500993] WARNING: CPU: 19 PID: 100 at kernel/rcu/tree_nocb.h:1061
> > rcu_nocb_rdp_deoffload+0x292/0x2a0
> > > [18839.503545] Modules linked in:
> > > [18839.504443] CPU: 19 UID: 0 PID: 100 Comm: rcu_nocb_toggle Not tainted
> > 6.11.0-rc3-00459-gba3eb80edec7-dirty #1553
> > > [18839.507190] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
> > rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> > > [18839.510002] RIP: 0010:rcu_nocb_rdp_deoffload+0x292/0x2a0
> > > [18839.511451] Code: e9 3c ff ff ff 4c 89 e6 48 89 ef e8 98 0d e1 00 e9
> > 3b fe ff ff 90 0f 0b 90 48 8b 83 c0 00 00 00 48 85 c0 0f 84 0b fe ff ff 90
> > <0f> 0b 90 e9 02 fe ff ff e8 e1 60 e0 00 90 90 90 90 90 90 90 90 90
> > > [18839.516469] RSP: 0000:ffffa05a8049be30 EFLAGS: 00010006
> > > [18839.517908] RAX: 0000000000000081 RBX: ffff956c5eaaf480 RCX:
> > 0000000000000000
> > > [18839.519849] RDX: 0000000000000001 RSI: 0000000000000287 RDI:
> > ffff956c5eaaf5f0
> > > [18839.521804] RBP: ffff956c5eaaf5f0 R08: 0000112269aee7fd R09:
> > 0000000000000001
> > > [18839.523747] R10: 00000000000020e8 R11: 0000000000000000 R12:
> > 0000000000000292
> > > [18839.525623] R13: 0000000000000000 R14: ffff956c5ea2f480 R15:
> > 0000000000000001
> > > [18839.527557] FS: 0000000000000000(0000) GS:ffff956c5eec0000(0000)
> > knlGS:0000000000000000
> > > [18839.529917] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > [18839.531556] CR2: 0000000000000000 CR3: 0000000001cfa000 CR4:
> > 00000000000006f0
> > > [18839.533495] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> > 0000000000000000
> > > [18839.535395] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> > 0000000000000400
> > > [18839.537322] Call Trace:
> > > [18839.538006] <TASK>
> > > [18839.538596] ? __warn+0x7e/0x120
> > > [18839.539491] ? rcu_nocb_rdp_deoffload+0x292/0x2a0
> > > [18839.540757] ? report_bug+0x18e/0x1a0
> > > [18839.541805] ? handle_bug+0x3d/0x70
> > > [18839.542837] ? exc_invalid_op+0x18/0x70
> > > [18839.543959] ? asm_exc_invalid_op+0x1a/0x20
> > > [18839.545165] ? rcu_nocb_rdp_deoffload+0x292/0x2a0
> > > [18839.546547] rcu_nocb_cpu_deoffload+0x70/0xa0
> > > [18839.547814] rcu_nocb_toggle+0x136/0x1c0
> > > [18839.548960] ? __pfx_rcu_nocb_toggle+0x10/0x10
> > > [18839.550073] kthread+0xd1/0x100
> > > [18839.550958] ? __pfx_kthread+0x10/0x10
> > > [18839.552008] ret_from_fork+0x2f/0x50
> > > [18839.553002] ? __pfx_kthread+0x10/0x10
> > > [18839.553968] ret_from_fork_asm+0x1a/0x30
> > > [18839.555038] </TASK>
> > >
> > >
> >
> >
