* kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
@ 2017-04-25 20:13 Ross Zwisler
2017-04-25 20:28 ` Paul E. McKenney
0 siblings, 1 reply; 6+ messages in thread
From: Ross Zwisler @ 2017-04-25 20:13 UTC (permalink / raw)
To: linux-ext4, Jan Kara, Theodore Ts'o
Cc: linux-kernel, Paul E. McKenney, Josh Triplett
I hit this RCU warning while running mkfs.ext4 on a PMEM namespace with
an unmodified v4.11-rc8 (passed through kasan_symbolize.py):
===============================
[ ERR: suspicious RCU usage. ]
4.11.0-rc8 #1 Not tainted
-------------------------------
kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 0
no locks held by mkfs.ext4/18493.
stack backtrace:
CPU: 10 PID: 18493 Comm: mkfs.ext4 Not tainted 4.11.0-rc8 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014
Call Trace:
[< inline >] __dump_stack project/linux/lib/dump_stack.c:16
[< none >] dump_stack+0x86/0xc3 project/linux/lib/dump_stack.c:52
[< none >] lockdep_rcu_suspicious+0xd7/0x110 project/linux/kernel/locking/lockdep.c:4461
[< none >] rcu_irq_enter+0x74/0x80 project/linux/kernel/rcu/tree.c:1031
[< none >] kvm_async_pf_task_wait+0x1af/0x240 project/linux/arch/x86/kernel/kvm.c:164
[< none >] do_async_page_fault+0x63/0x90 project/linux/arch/x86/kernel/kvm.c:269
?[< none >] do_async_page_fault+0x63/0x90 project/linux/arch/x86/kernel/kvm.c:269
[< none >] async_page_fault+0x28/0x30 project/linux_2/arch/x86/entry/entry_64.S:1014
RIP: 0010:copy_user_enhanced_fast_string+0x5/0x10
RSP: 0018:ffffc90008777c90 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000001000 RCX: 0000000000001000
RDX: 0000000000001000 RSI: 00007f42a5d88010 RDI: ffff88007e82d000
RBP: ffffc90008777ce0 R08: ffff88007e82d000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffea0001fa0b40 R12: 0000000000001000
R13: ffffc90008777e50 R14: ffff88007e82e000 R15: 0000000000001000
?[< inline >] copy_user_generic project/linux/./arch/x86/include/asm/uaccess_64.h:37
?[< inline >] __copy_from_user_nocheck project/linux/./arch/x86/include/asm/uaccess_64.h:59
?[< inline >] __copy_from_user_inatomic project/linux/./arch/x86/include/asm/uaccess_64.h:251
?[< none >] iov_iter_copy_from_user_atomic+0xbb/0x350 project/linux/lib/iov_iter.c:721
[< none >] generic_perform_write+0xf2/0x1d0 project/linux/mm/filemap.c:2843
[< none >] __generic_file_write_iter+0x185/0x1c0 project/linux/mm/filemap.c:2960
[< none >] blkdev_write_iter+0x96/0x110 project/linux/fs/block_dev.c:2008
[< inline >] call_write_iter project/linux/./include/linux/fs.h:1733
[< inline >] new_sync_write project/linux/fs/read_write.c:497
[< none >] __vfs_write+0xe8/0x160 project/linux/fs/read_write.c:510
?[< inline >] call_write_iter project/linux/./include/linux/fs.h:1733
?[< inline >] new_sync_write project/linux/fs/read_write.c:497
?[< none >] __vfs_write+0xe8/0x160 project/linux/fs/read_write.c:510
[< none >] vfs_write+0xcb/0x1f0 project/linux/fs/read_write.c:558
[< inline >] SYSC_pwrite64 project/linux/fs/read_write.c:647
[< none >] SyS_pwrite64+0x98/0xc0 project/linux/fs/read_write.c:634
[< none >] entry_SYSCALL_64_fastpath+0x1f/0xc2 project/linux_2/arch/x86/entry/entry_64.S:204
RIP: 0033:0x7f42acd4d213
RSP: 002b:00007ffc846e4e38 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f42acd4d213
RDX: 00000000001e0000 RSI: 00007f42a5c9f010 RDI: 0000000000000003
RBP: 0000559bd6c46380 R08: 00007f42a5c9f010 R09: 0000000000000200
R10: 0000000680820000 R11: 0000000000000246 R12: 00007ffc846e4f9c
R13: 0000000000000425 R14: 0000000000000200 R15: 0000559bd6c46380
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
2017-04-25 20:13 kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!! Ross Zwisler
@ 2017-04-25 20:28 ` Paul E. McKenney
2017-04-26 7:16 ` Jan Kara
0 siblings, 1 reply; 6+ messages in thread
From: Paul E. McKenney @ 2017-04-25 20:28 UTC (permalink / raw)
To: Ross Zwisler
Cc: linux-ext4, Jan Kara, Theodore Ts'o, linux-kernel, Josh Triplett
On Tue, Apr 25, 2017 at 02:13:45PM -0600, Ross Zwisler wrote:
> I hit this RCU warning while running mkfs.ext4 on a PMEM namespace with
> an unmodified v4.11-rc8 (passed through kasan_symbolize.py):
>
> ===============================
> [ ERR: suspicious RCU usage. ]
> 4.11.0-rc8 #1 Not tainted
> -------------------------------
> kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
Just in case there is any doubt, invoking rcu_irq_enter() with irqs
enabled voids your kernel's RCU warranty. ;-)
So please don't do that.
Thanx, Paul
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 2, debug_locks = 0
> no locks held by mkfs.ext4/18493.
>
> stack backtrace:
> CPU: 10 PID: 18493 Comm: mkfs.ext4 Not tainted 4.11.0-rc8 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014
> Call Trace:
> [< inline >] __dump_stack project/linux/lib/dump_stack.c:16
> [< none >] dump_stack+0x86/0xc3 project/linux/lib/dump_stack.c:52
> [< none >] lockdep_rcu_suspicious+0xd7/0x110 project/linux/kernel/locking/lockdep.c:4461
> [< none >] rcu_irq_enter+0x74/0x80 project/linux/kernel/rcu/tree.c:1031
> [< none >] kvm_async_pf_task_wait+0x1af/0x240 project/linux/arch/x86/kernel/kvm.c:164
> [< none >] do_async_page_fault+0x63/0x90 project/linux/arch/x86/kernel/kvm.c:269
> ?[< none >] do_async_page_fault+0x63/0x90 project/linux/arch/x86/kernel/kvm.c:269
> [< none >] async_page_fault+0x28/0x30 project/linux_2/arch/x86/entry/entry_64.S:1014
> RIP: 0010:copy_user_enhanced_fast_string+0x5/0x10
> RSP: 0018:ffffc90008777c90 EFLAGS: 00010202
> RAX: 0000000000000001 RBX: 0000000000001000 RCX: 0000000000001000
> RDX: 0000000000001000 RSI: 00007f42a5d88010 RDI: ffff88007e82d000
> RBP: ffffc90008777ce0 R08: ffff88007e82d000 R09: 0000000000000000
> R10: 0000000000000000 R11: ffffea0001fa0b40 R12: 0000000000001000
> R13: ffffc90008777e50 R14: ffff88007e82e000 R15: 0000000000001000
> ?[< inline >] copy_user_generic project/linux/./arch/x86/include/asm/uaccess_64.h:37
> ?[< inline >] __copy_from_user_nocheck project/linux/./arch/x86/include/asm/uaccess_64.h:59
> ?[< inline >] __copy_from_user_inatomic project/linux/./arch/x86/include/asm/uaccess_64.h:251
> ?[< none >] iov_iter_copy_from_user_atomic+0xbb/0x350 project/linux/lib/iov_iter.c:721
> [< none >] generic_perform_write+0xf2/0x1d0 project/linux/mm/filemap.c:2843
> [< none >] __generic_file_write_iter+0x185/0x1c0 project/linux/mm/filemap.c:2960
> [< none >] blkdev_write_iter+0x96/0x110 project/linux/fs/block_dev.c:2008
> [< inline >] call_write_iter project/linux/./include/linux/fs.h:1733
> [< inline >] new_sync_write project/linux/fs/read_write.c:497
> [< none >] __vfs_write+0xe8/0x160 project/linux/fs/read_write.c:510
> ?[< inline >] call_write_iter project/linux/./include/linux/fs.h:1733
> ?[< inline >] new_sync_write project/linux/fs/read_write.c:497
> ?[< none >] __vfs_write+0xe8/0x160 project/linux/fs/read_write.c:510
> [< none >] vfs_write+0xcb/0x1f0 project/linux/fs/read_write.c:558
> [< inline >] SYSC_pwrite64 project/linux/fs/read_write.c:647
> [< none >] SyS_pwrite64+0x98/0xc0 project/linux/fs/read_write.c:634
> [< none >] entry_SYSCALL_64_fastpath+0x1f/0xc2 project/linux_2/arch/x86/entry/entry_64.S:204
> RIP: 0033:0x7f42acd4d213
> RSP: 002b:00007ffc846e4e38 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f42acd4d213
> RDX: 00000000001e0000 RSI: 00007f42a5c9f010 RDI: 0000000000000003
> RBP: 0000559bd6c46380 R08: 00007f42a5c9f010 R09: 0000000000000200
> R10: 0000000680820000 R11: 0000000000000246 R12: 00007ffc846e4f9c
> R13: 0000000000000425 R14: 0000000000000200 R15: 0000559bd6c46380
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
2017-04-25 20:28 ` Paul E. McKenney
@ 2017-04-26 7:16 ` Jan Kara
2017-04-26 14:18 ` Radim Krčmář
0 siblings, 1 reply; 6+ messages in thread
From: Jan Kara @ 2017-04-26 7:16 UTC (permalink / raw)
To: Paul E. McKenney
Cc: Ross Zwisler, linux-ext4, Jan Kara, Theodore Ts'o,
linux-kernel, Josh Triplett, kvm, Paolo Bonzini,
Radim Krčmář
On Tue 25-04-17 13:28:41, Paul E. McKenney wrote:
> On Tue, Apr 25, 2017 at 02:13:45PM -0600, Ross Zwisler wrote:
> > I hit this RCU warning while running mkfs.ext4 on a PMEM namespace with
> > an unmodified v4.11-rc8 (passed through kasan_symbolize.py):
> >
> > ===============================
> > [ ERR: suspicious RCU usage. ]
> > 4.11.0-rc8 #1 Not tainted
> > -------------------------------
> > kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
>
> Just in case there is any doubt, invoking rcu_irq_enter() with irqs
> enabled voids your kernel's RCU warranty. ;-)
>
> So please don't do that.
OK, but looking at the stack trace, this has nothing to do with ext4. The
problem seems to be in KVM - relevant CCs added.
Honza
>
> > other info that might help us debug this:
> >
> >
> > rcu_scheduler_active = 2, debug_locks = 0
> > no locks held by mkfs.ext4/18493.
> >
> > stack backtrace:
> > CPU: 10 PID: 18493 Comm: mkfs.ext4 Not tainted 4.11.0-rc8 #1
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014
> > Call Trace:
> > [< inline >] __dump_stack project/linux/lib/dump_stack.c:16
> > [< none >] dump_stack+0x86/0xc3 project/linux/lib/dump_stack.c:52
> > [< none >] lockdep_rcu_suspicious+0xd7/0x110 project/linux/kernel/locking/lockdep.c:4461
> > [< none >] rcu_irq_enter+0x74/0x80 project/linux/kernel/rcu/tree.c:1031
> > [< none >] kvm_async_pf_task_wait+0x1af/0x240 project/linux/arch/x86/kernel/kvm.c:164
> > [< none >] do_async_page_fault+0x63/0x90 project/linux/arch/x86/kernel/kvm.c:269
> > ?[< none >] do_async_page_fault+0x63/0x90 project/linux/arch/x86/kernel/kvm.c:269
> > [< none >] async_page_fault+0x28/0x30 project/linux_2/arch/x86/entry/entry_64.S:1014
> > RIP: 0010:copy_user_enhanced_fast_string+0x5/0x10
> > RSP: 0018:ffffc90008777c90 EFLAGS: 00010202
> > RAX: 0000000000000001 RBX: 0000000000001000 RCX: 0000000000001000
> > RDX: 0000000000001000 RSI: 00007f42a5d88010 RDI: ffff88007e82d000
> > RBP: ffffc90008777ce0 R08: ffff88007e82d000 R09: 0000000000000000
> > R10: 0000000000000000 R11: ffffea0001fa0b40 R12: 0000000000001000
> > R13: ffffc90008777e50 R14: ffff88007e82e000 R15: 0000000000001000
> > ?[< inline >] copy_user_generic project/linux/./arch/x86/include/asm/uaccess_64.h:37
> > ?[< inline >] __copy_from_user_nocheck project/linux/./arch/x86/include/asm/uaccess_64.h:59
> > ?[< inline >] __copy_from_user_inatomic project/linux/./arch/x86/include/asm/uaccess_64.h:251
> > ?[< none >] iov_iter_copy_from_user_atomic+0xbb/0x350 project/linux/lib/iov_iter.c:721
> > [< none >] generic_perform_write+0xf2/0x1d0 project/linux/mm/filemap.c:2843
> > [< none >] __generic_file_write_iter+0x185/0x1c0 project/linux/mm/filemap.c:2960
> > [< none >] blkdev_write_iter+0x96/0x110 project/linux/fs/block_dev.c:2008
> > [< inline >] call_write_iter project/linux/./include/linux/fs.h:1733
> > [< inline >] new_sync_write project/linux/fs/read_write.c:497
> > [< none >] __vfs_write+0xe8/0x160 project/linux/fs/read_write.c:510
> > ?[< inline >] call_write_iter project/linux/./include/linux/fs.h:1733
> > ?[< inline >] new_sync_write project/linux/fs/read_write.c:497
> > ?[< none >] __vfs_write+0xe8/0x160 project/linux/fs/read_write.c:510
> > [< none >] vfs_write+0xcb/0x1f0 project/linux/fs/read_write.c:558
> > [< inline >] SYSC_pwrite64 project/linux/fs/read_write.c:647
> > [< none >] SyS_pwrite64+0x98/0xc0 project/linux/fs/read_write.c:634
> > [< none >] entry_SYSCALL_64_fastpath+0x1f/0xc2 project/linux_2/arch/x86/entry/entry_64.S:204
> > RIP: 0033:0x7f42acd4d213
> > RSP: 002b:00007ffc846e4e38 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
> > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f42acd4d213
> > RDX: 00000000001e0000 RSI: 00007f42a5c9f010 RDI: 0000000000000003
> > RBP: 0000559bd6c46380 R08: 00007f42a5c9f010 R09: 0000000000000200
> > R10: 0000000680820000 R11: 0000000000000246 R12: 00007ffc846e4f9c
> > R13: 0000000000000425 R14: 0000000000000200 R15: 0000559bd6c46380
> >
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
2017-04-26 7:16 ` Jan Kara
@ 2017-04-26 14:18 ` Radim Krčmář
2017-04-26 14:29 ` Paolo Bonzini
0 siblings, 1 reply; 6+ messages in thread
From: Radim Krčmář @ 2017-04-26 14:18 UTC (permalink / raw)
To: Jan Kara
Cc: Paul E. McKenney, Ross Zwisler, linux-ext4, Theodore Ts'o,
linux-kernel, Josh Triplett, kvm, Paolo Bonzini
2017-04-26 09:16+0200, Jan Kara:
> On Tue 25-04-17 13:28:41, Paul E. McKenney wrote:
> > On Tue, Apr 25, 2017 at 02:13:45PM -0600, Ross Zwisler wrote:
> > > I hit this RCU warning while running mkfs.ext4 on a PMEM namespace with
> > > an unmodified v4.11-rc8 (passed through kasan_symbolize.py):
> > >
> > > ===============================
> > > [ ERR: suspicious RCU usage. ]
> > > 4.11.0-rc8 #1 Not tainted
> > > -------------------------------
> > > kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
> >
> > Just in case there is any doubt, invoking rcu_irq_enter() with irqs
> > enabled voids your kernel's RCU warranty. ;-)
> >
> > So please don't do that.
>
> OK, but looking at the stack trace, this has nothing to do with ext4. The
> problem seems to be in KVM - relevant CCs added.
The path begins with async_page_fault interrupt gate and the hardware
should clear the interrupt flag before executing it. I don't see a
change that would break the assumption that interrupts are disabled ...
Paul, is it a regression since v4.10?
It might be a fault of the host KVM that interrupts are enabled -- what
is the host cpu and kernel version?
Thanks.
>
> Honza
>
> >
> > > other info that might help us debug this:
> > >
> > >
> > > rcu_scheduler_active = 2, debug_locks = 0
> > > no locks held by mkfs.ext4/18493.
> > >
> > > stack backtrace:
> > > CPU: 10 PID: 18493 Comm: mkfs.ext4 Not tainted 4.11.0-rc8 #1
> > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014
> > > Call Trace:
> > > [< inline >] __dump_stack project/linux/lib/dump_stack.c:16
> > > [< none >] dump_stack+0x86/0xc3 project/linux/lib/dump_stack.c:52
> > > [< none >] lockdep_rcu_suspicious+0xd7/0x110 project/linux/kernel/locking/lockdep.c:4461
> > > [< none >] rcu_irq_enter+0x74/0x80 project/linux/kernel/rcu/tree.c:1031
> > > [< none >] kvm_async_pf_task_wait+0x1af/0x240 project/linux/arch/x86/kernel/kvm.c:164
> > > [< none >] do_async_page_fault+0x63/0x90 project/linux/arch/x86/kernel/kvm.c:269
> > > ?[< none >] do_async_page_fault+0x63/0x90 project/linux/arch/x86/kernel/kvm.c:269
> > > [< none >] async_page_fault+0x28/0x30 project/linux_2/arch/x86/entry/entry_64.S:1014
> > > RIP: 0010:copy_user_enhanced_fast_string+0x5/0x10
> > > RSP: 0018:ffffc90008777c90 EFLAGS: 00010202
> > > RAX: 0000000000000001 RBX: 0000000000001000 RCX: 0000000000001000
> > > RDX: 0000000000001000 RSI: 00007f42a5d88010 RDI: ffff88007e82d000
> > > RBP: ffffc90008777ce0 R08: ffff88007e82d000 R09: 0000000000000000
> > > R10: 0000000000000000 R11: ffffea0001fa0b40 R12: 0000000000001000
> > > R13: ffffc90008777e50 R14: ffff88007e82e000 R15: 0000000000001000
> > > ?[< inline >] copy_user_generic project/linux/./arch/x86/include/asm/uaccess_64.h:37
> > > ?[< inline >] __copy_from_user_nocheck project/linux/./arch/x86/include/asm/uaccess_64.h:59
> > > ?[< inline >] __copy_from_user_inatomic project/linux/./arch/x86/include/asm/uaccess_64.h:251
> > > ?[< none >] iov_iter_copy_from_user_atomic+0xbb/0x350 project/linux/lib/iov_iter.c:721
> > > [< none >] generic_perform_write+0xf2/0x1d0 project/linux/mm/filemap.c:2843
> > > [< none >] __generic_file_write_iter+0x185/0x1c0 project/linux/mm/filemap.c:2960
> > > [< none >] blkdev_write_iter+0x96/0x110 project/linux/fs/block_dev.c:2008
> > > [< inline >] call_write_iter project/linux/./include/linux/fs.h:1733
> > > [< inline >] new_sync_write project/linux/fs/read_write.c:497
> > > [< none >] __vfs_write+0xe8/0x160 project/linux/fs/read_write.c:510
> > > ?[< inline >] call_write_iter project/linux/./include/linux/fs.h:1733
> > > ?[< inline >] new_sync_write project/linux/fs/read_write.c:497
> > > ?[< none >] __vfs_write+0xe8/0x160 project/linux/fs/read_write.c:510
> > > [< none >] vfs_write+0xcb/0x1f0 project/linux/fs/read_write.c:558
> > > [< inline >] SYSC_pwrite64 project/linux/fs/read_write.c:647
> > > [< none >] SyS_pwrite64+0x98/0xc0 project/linux/fs/read_write.c:634
> > > [< none >] entry_SYSCALL_64_fastpath+0x1f/0xc2 project/linux_2/arch/x86/entry/entry_64.S:204
> > > RIP: 0033:0x7f42acd4d213
> > > RSP: 002b:00007ffc846e4e38 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
> > > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f42acd4d213
> > > RDX: 00000000001e0000 RSI: 00007f42a5c9f010 RDI: 0000000000000003
> > > RBP: 0000559bd6c46380 R08: 00007f42a5c9f010 R09: 0000000000000200
> > > R10: 0000000680820000 R11: 0000000000000246 R12: 00007ffc846e4f9c
> > > R13: 0000000000000425 R14: 0000000000000200 R15: 0000559bd6c46380
> > >
> >
> --
> Jan Kara <jack@suse.com>
> SUSE Labs, CR
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
2017-04-26 14:18 ` Radim Krčmář
@ 2017-04-26 14:29 ` Paolo Bonzini
2017-04-26 14:39 ` Radim Krčmář
0 siblings, 1 reply; 6+ messages in thread
From: Paolo Bonzini @ 2017-04-26 14:29 UTC (permalink / raw)
To: Radim Krčmář, Jan Kara
Cc: Paul E. McKenney, Ross Zwisler, linux-ext4, Theodore Ts'o,
linux-kernel, Josh Triplett, kvm
On 26/04/2017 16:18, Radim Krčmář wrote:
>> OK, but looking at the stack trace, this has nothing to do with ext4. The
>> problem seems to be in KVM - relevant CCs added.
> The path begins with async_page_fault interrupt gate and the hardware
> should clear the interrupt flag before executing it. I don't see a
> change that would break the assumption that interrupts are disabled ...
native_safe_halt enables interrupts. I think this is it:
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 14f65a5f938e..2a7835932b71 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -161,8 +161,8 @@ void kvm_async_pf_task_wait(u32 token)
*/
rcu_irq_exit();
native_safe_halt();
- rcu_irq_enter();
local_irq_disable();
+ rcu_irq_enter();
}
}
if (!n.halted)
Paolo
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!!
2017-04-26 14:29 ` Paolo Bonzini
@ 2017-04-26 14:39 ` Radim Krčmář
0 siblings, 0 replies; 6+ messages in thread
From: Radim Krčmář @ 2017-04-26 14:39 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Jan Kara, Paul E. McKenney, Ross Zwisler, linux-ext4,
Theodore Ts'o, linux-kernel, Josh Triplett, kvm
2017-04-26 16:29+0200, Paolo Bonzini:
> On 26/04/2017 16:18, Radim Krčmář wrote:
>>> OK, but looking at the stack trace, this has nothing to do with ext4. The
>>> problem seems to be in KVM - relevant CCs added.
>> The path begins with async_page_fault interrupt gate and the hardware
>> should clear the interrupt flag before executing it. I don't see a
>> change that would break the assumption that interrupts are disabled ...
>
> native_safe_halt enables interrupts. I think this is it:
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 14f65a5f938e..2a7835932b71 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -161,8 +161,8 @@ void kvm_async_pf_task_wait(u32 token)
> */
> rcu_irq_exit();
> native_safe_halt();
> - rcu_irq_enter();
> local_irq_disable();
> + rcu_irq_enter();
> }
> }
> if (!n.halted)
We called rcu_irq_enter() there twice, *facepalm*.
Yes, that patch should fix it.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-04-26 14:39 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2017-04-25 20:13 kernel/rcu/tree.c:1031 rcu_irq_enter() invoked with irqs enabled!!!! Ross Zwisler
2017-04-25 20:28 ` Paul E. McKenney
2017-04-26 7:16 ` Jan Kara
2017-04-26 14:18 ` Radim Krčmář
2017-04-26 14:29 ` Paolo Bonzini
2017-04-26 14:39 ` Radim Krčmář
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