drivers/xen/preempt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
For support of long running hypercalls xen_maybe_preempt_hcall() is
calling cond_resched() in case a hypercall marked as preemptible has
been interrupted.
Normally this is no problem, as only hypercalls done via some ioctl()s
are marked to be preemptible. In rare cases when during such a
preemptible hypercall an interrupt occurs and any softirq action is
started from irq_exit(), a further hypercall issued by the softirq
handler will be regarded to be preemptible, too. This might lead to
rescheduling in spite of the softirq handler potentially having set
preempt_disable(), leading to splats like:
BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl
INFO: lockdep is turned off.
CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1
Call Trace:
<IRQ>
dump_stack+0x8f/0xd0
___might_sleep.cold.76+0xb2/0x103
xen_maybe_preempt_hcall+0x48/0x70
xen_do_hypervisor_callback+0x37/0x40
RIP: e030:xen_hypercall_xen_version+0xa/0x20
Code: ...
RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246
RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a
RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0
R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000
? xen_hypercall_xen_version+0xa/0x20
? xen_force_evtchn_callback+0x9/0x10
? check_events+0x12/0x20
? xen_restore_fl_direct+0x1f/0x20
? _raw_spin_unlock_irqrestore+0x53/0x60
? debug_dma_sync_single_for_cpu+0x91/0xc0
? _raw_spin_unlock_irqrestore+0x53/0x60
? xen_swiotlb_sync_single_for_cpu+0x3d/0x140
? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en]
? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en]
? net_rx_action+0x151/0x4a0
? __do_softirq+0xed/0x55b
? irq_exit+0xea/0x100
? xen_evtchn_do_upcall+0x2c/0x40
? xen_do_hypervisor_callback+0x29/0x40
</IRQ>
? xen_hypercall_domctl+0xa/0x20
? xen_hypercall_domctl+0x8/0x20
? privcmd_ioctl+0x221/0x990 [xen_privcmd]
? do_vfs_ioctl+0xa5/0x6f0
? ksys_ioctl+0x60/0x90
? trace_hardirqs_off_thunk+0x1a/0x20
? __x64_sys_ioctl+0x16/0x20
? do_syscall_64+0x62/0x250
? entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fix that by testing preempt_count() before calling cond_resched().
In kernel 5.8 this can't happen any more due to the entry code rework
(more than 100 patches, so not a candidate for backporting).
The issue was introduced in kernel 4.3, so this patch should go into
all stable kernels in [4.3 ... 5.7].
Reported-by: Sarah Newman <srn@prgmr.com>
Fixes: 0fa2f5cb2b0ecd8 ("sched/preempt, xen: Use need_resched() instead of should_resched()")
Cc: Sarah Newman <srn@prgmr.com>
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Chris Brannon <cmb@prgmr.com>
---
drivers/xen/preempt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/xen/preempt.c b/drivers/xen/preempt.c
index 17240c5325a3..6ad87b5c95ed 100644
--- a/drivers/xen/preempt.c
+++ b/drivers/xen/preempt.c
@@ -27,7 +27,7 @@ EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall);
asmlinkage __visible void xen_maybe_preempt_hcall(void)
{
if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
- && need_resched())) {
+ && need_resched() && !preempt_count())) {
/*
* Clear flag as we may be rescheduled on a different
* cpu.
--
2.26.2
On Thu, Aug 20, 2020 at 08:59:08AM +0200, Juergen Gross wrote: > For support of long running hypercalls xen_maybe_preempt_hcall() is > calling cond_resched() in case a hypercall marked as preemptible has > been interrupted. > > Normally this is no problem, as only hypercalls done via some ioctl()s > are marked to be preemptible. In rare cases when during such a > preemptible hypercall an interrupt occurs and any softirq action is > started from irq_exit(), a further hypercall issued by the softirq > handler will be regarded to be preemptible, too. This might lead to > rescheduling in spite of the softirq handler potentially having set > preempt_disable(), leading to splats like: > > BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37 > in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl > INFO: lockdep is turned off. > CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1 > Call Trace: > <IRQ> > dump_stack+0x8f/0xd0 > ___might_sleep.cold.76+0xb2/0x103 > xen_maybe_preempt_hcall+0x48/0x70 > xen_do_hypervisor_callback+0x37/0x40 > RIP: e030:xen_hypercall_xen_version+0xa/0x20 > Code: ... > RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246 > RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a > RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001 > R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0 > R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000 > ? xen_hypercall_xen_version+0xa/0x20 > ? xen_force_evtchn_callback+0x9/0x10 > ? check_events+0x12/0x20 > ? xen_restore_fl_direct+0x1f/0x20 > ? _raw_spin_unlock_irqrestore+0x53/0x60 > ? debug_dma_sync_single_for_cpu+0x91/0xc0 > ? _raw_spin_unlock_irqrestore+0x53/0x60 > ? xen_swiotlb_sync_single_for_cpu+0x3d/0x140 > ? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en] > ? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en] > ? net_rx_action+0x151/0x4a0 > ? __do_softirq+0xed/0x55b > ? irq_exit+0xea/0x100 > ? xen_evtchn_do_upcall+0x2c/0x40 > ? xen_do_hypervisor_callback+0x29/0x40 > </IRQ> > ? xen_hypercall_domctl+0xa/0x20 > ? xen_hypercall_domctl+0x8/0x20 > ? privcmd_ioctl+0x221/0x990 [xen_privcmd] > ? do_vfs_ioctl+0xa5/0x6f0 > ? ksys_ioctl+0x60/0x90 > ? trace_hardirqs_off_thunk+0x1a/0x20 > ? __x64_sys_ioctl+0x16/0x20 > ? do_syscall_64+0x62/0x250 > ? entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Fix that by testing preempt_count() before calling cond_resched(). > > In kernel 5.8 this can't happen any more due to the entry code rework > (more than 100 patches, so not a candidate for backporting). > > The issue was introduced in kernel 4.3, so this patch should go into > all stable kernels in [4.3 ... 5.7]. Now queued up, thanks! greg k-h
This is a note to let you know that I've just added the patch titled
xen: don't reschedule in preemption off sections
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-don-t-reschedule-in-preemption-off-sections.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
From jgross@suse.com Mon Aug 24 10:12:00 2020
From: Juergen Gross <jgross@suse.com>
Date: Thu, 20 Aug 2020 08:59:08 +0200
Subject: xen: don't reschedule in preemption off sections
To: stable@vger.kernel.org
Cc: xen-devel@lists.xenproject.org, Juergen Gross <jgross@suse.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Stefano Stabellini <sstabellini@kernel.org>, Sarah Newman <srn@prgmr.com>, Chris Brannon <cmb@prgmr.com>
Message-ID: <20200820065908.20592-1-jgross@suse.com>
From: Juergen Gross <jgross@suse.com>
For support of long running hypercalls xen_maybe_preempt_hcall() is
calling cond_resched() in case a hypercall marked as preemptible has
been interrupted.
Normally this is no problem, as only hypercalls done via some ioctl()s
are marked to be preemptible. In rare cases when during such a
preemptible hypercall an interrupt occurs and any softirq action is
started from irq_exit(), a further hypercall issued by the softirq
handler will be regarded to be preemptible, too. This might lead to
rescheduling in spite of the softirq handler potentially having set
preempt_disable(), leading to splats like:
BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl
INFO: lockdep is turned off.
CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1
Call Trace:
<IRQ>
dump_stack+0x8f/0xd0
___might_sleep.cold.76+0xb2/0x103
xen_maybe_preempt_hcall+0x48/0x70
xen_do_hypervisor_callback+0x37/0x40
RIP: e030:xen_hypercall_xen_version+0xa/0x20
Code: ...
RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246
RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a
RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0
R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000
? xen_hypercall_xen_version+0xa/0x20
? xen_force_evtchn_callback+0x9/0x10
? check_events+0x12/0x20
? xen_restore_fl_direct+0x1f/0x20
? _raw_spin_unlock_irqrestore+0x53/0x60
? debug_dma_sync_single_for_cpu+0x91/0xc0
? _raw_spin_unlock_irqrestore+0x53/0x60
? xen_swiotlb_sync_single_for_cpu+0x3d/0x140
? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en]
? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en]
? net_rx_action+0x151/0x4a0
? __do_softirq+0xed/0x55b
? irq_exit+0xea/0x100
? xen_evtchn_do_upcall+0x2c/0x40
? xen_do_hypervisor_callback+0x29/0x40
</IRQ>
? xen_hypercall_domctl+0xa/0x20
? xen_hypercall_domctl+0x8/0x20
? privcmd_ioctl+0x221/0x990 [xen_privcmd]
? do_vfs_ioctl+0xa5/0x6f0
? ksys_ioctl+0x60/0x90
? trace_hardirqs_off_thunk+0x1a/0x20
? __x64_sys_ioctl+0x16/0x20
? do_syscall_64+0x62/0x250
? entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fix that by testing preempt_count() before calling cond_resched().
In kernel 5.8 this can't happen any more due to the entry code rework
(more than 100 patches, so not a candidate for backporting).
The issue was introduced in kernel 4.3, so this patch should go into
all stable kernels in [4.3 ... 5.7].
Reported-by: Sarah Newman <srn@prgmr.com>
Fixes: 0fa2f5cb2b0ecd8 ("sched/preempt, xen: Use need_resched() instead of should_resched()")
Cc: Sarah Newman <srn@prgmr.com>
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Chris Brannon <cmb@prgmr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/xen/preempt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/xen/preempt.c
+++ b/drivers/xen/preempt.c
@@ -31,7 +31,7 @@ EXPORT_SYMBOL_GPL(xen_in_preemptible_hca
asmlinkage __visible void xen_maybe_preempt_hcall(void)
{
if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
- && need_resched())) {
+ && need_resched() && !preempt_count())) {
/*
* Clear flag as we may be rescheduled on a different
* cpu.
Patches currently in stable-queue which might be from jgross@suse.com are
queue-4.4/xen-don-t-reschedule-in-preemption-off-sections.patch
This is a note to let you know that I've just added the patch titled
xen: don't reschedule in preemption off sections
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-don-t-reschedule-in-preemption-off-sections.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
From jgross@suse.com Mon Aug 24 10:12:00 2020
From: Juergen Gross <jgross@suse.com>
Date: Thu, 20 Aug 2020 08:59:08 +0200
Subject: xen: don't reschedule in preemption off sections
To: stable@vger.kernel.org
Cc: xen-devel@lists.xenproject.org, Juergen Gross <jgross@suse.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Stefano Stabellini <sstabellini@kernel.org>, Sarah Newman <srn@prgmr.com>, Chris Brannon <cmb@prgmr.com>
Message-ID: <20200820065908.20592-1-jgross@suse.com>
From: Juergen Gross <jgross@suse.com>
For support of long running hypercalls xen_maybe_preempt_hcall() is
calling cond_resched() in case a hypercall marked as preemptible has
been interrupted.
Normally this is no problem, as only hypercalls done via some ioctl()s
are marked to be preemptible. In rare cases when during such a
preemptible hypercall an interrupt occurs and any softirq action is
started from irq_exit(), a further hypercall issued by the softirq
handler will be regarded to be preemptible, too. This might lead to
rescheduling in spite of the softirq handler potentially having set
preempt_disable(), leading to splats like:
BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl
INFO: lockdep is turned off.
CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1
Call Trace:
<IRQ>
dump_stack+0x8f/0xd0
___might_sleep.cold.76+0xb2/0x103
xen_maybe_preempt_hcall+0x48/0x70
xen_do_hypervisor_callback+0x37/0x40
RIP: e030:xen_hypercall_xen_version+0xa/0x20
Code: ...
RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246
RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a
RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0
R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000
? xen_hypercall_xen_version+0xa/0x20
? xen_force_evtchn_callback+0x9/0x10
? check_events+0x12/0x20
? xen_restore_fl_direct+0x1f/0x20
? _raw_spin_unlock_irqrestore+0x53/0x60
? debug_dma_sync_single_for_cpu+0x91/0xc0
? _raw_spin_unlock_irqrestore+0x53/0x60
? xen_swiotlb_sync_single_for_cpu+0x3d/0x140
? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en]
? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en]
? net_rx_action+0x151/0x4a0
? __do_softirq+0xed/0x55b
? irq_exit+0xea/0x100
? xen_evtchn_do_upcall+0x2c/0x40
? xen_do_hypervisor_callback+0x29/0x40
</IRQ>
? xen_hypercall_domctl+0xa/0x20
? xen_hypercall_domctl+0x8/0x20
? privcmd_ioctl+0x221/0x990 [xen_privcmd]
? do_vfs_ioctl+0xa5/0x6f0
? ksys_ioctl+0x60/0x90
? trace_hardirqs_off_thunk+0x1a/0x20
? __x64_sys_ioctl+0x16/0x20
? do_syscall_64+0x62/0x250
? entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fix that by testing preempt_count() before calling cond_resched().
In kernel 5.8 this can't happen any more due to the entry code rework
(more than 100 patches, so not a candidate for backporting).
The issue was introduced in kernel 4.3, so this patch should go into
all stable kernels in [4.3 ... 5.7].
Reported-by: Sarah Newman <srn@prgmr.com>
Fixes: 0fa2f5cb2b0ecd8 ("sched/preempt, xen: Use need_resched() instead of should_resched()")
Cc: Sarah Newman <srn@prgmr.com>
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Chris Brannon <cmb@prgmr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/xen/preempt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/xen/preempt.c
+++ b/drivers/xen/preempt.c
@@ -31,7 +31,7 @@ EXPORT_SYMBOL_GPL(xen_in_preemptible_hca
asmlinkage __visible void xen_maybe_preempt_hcall(void)
{
if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
- && need_resched())) {
+ && need_resched() && !preempt_count())) {
/*
* Clear flag as we may be rescheduled on a different
* cpu.
Patches currently in stable-queue which might be from jgross@suse.com are
queue-4.9/xen-don-t-reschedule-in-preemption-off-sections.patch
This is a note to let you know that I've just added the patch titled
xen: don't reschedule in preemption off sections
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-don-t-reschedule-in-preemption-off-sections.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
From jgross@suse.com Mon Aug 24 10:12:00 2020
From: Juergen Gross <jgross@suse.com>
Date: Thu, 20 Aug 2020 08:59:08 +0200
Subject: xen: don't reschedule in preemption off sections
To: stable@vger.kernel.org
Cc: xen-devel@lists.xenproject.org, Juergen Gross <jgross@suse.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Stefano Stabellini <sstabellini@kernel.org>, Sarah Newman <srn@prgmr.com>, Chris Brannon <cmb@prgmr.com>
Message-ID: <20200820065908.20592-1-jgross@suse.com>
From: Juergen Gross <jgross@suse.com>
For support of long running hypercalls xen_maybe_preempt_hcall() is
calling cond_resched() in case a hypercall marked as preemptible has
been interrupted.
Normally this is no problem, as only hypercalls done via some ioctl()s
are marked to be preemptible. In rare cases when during such a
preemptible hypercall an interrupt occurs and any softirq action is
started from irq_exit(), a further hypercall issued by the softirq
handler will be regarded to be preemptible, too. This might lead to
rescheduling in spite of the softirq handler potentially having set
preempt_disable(), leading to splats like:
BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl
INFO: lockdep is turned off.
CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1
Call Trace:
<IRQ>
dump_stack+0x8f/0xd0
___might_sleep.cold.76+0xb2/0x103
xen_maybe_preempt_hcall+0x48/0x70
xen_do_hypervisor_callback+0x37/0x40
RIP: e030:xen_hypercall_xen_version+0xa/0x20
Code: ...
RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246
RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a
RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0
R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000
? xen_hypercall_xen_version+0xa/0x20
? xen_force_evtchn_callback+0x9/0x10
? check_events+0x12/0x20
? xen_restore_fl_direct+0x1f/0x20
? _raw_spin_unlock_irqrestore+0x53/0x60
? debug_dma_sync_single_for_cpu+0x91/0xc0
? _raw_spin_unlock_irqrestore+0x53/0x60
? xen_swiotlb_sync_single_for_cpu+0x3d/0x140
? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en]
? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en]
? net_rx_action+0x151/0x4a0
? __do_softirq+0xed/0x55b
? irq_exit+0xea/0x100
? xen_evtchn_do_upcall+0x2c/0x40
? xen_do_hypervisor_callback+0x29/0x40
</IRQ>
? xen_hypercall_domctl+0xa/0x20
? xen_hypercall_domctl+0x8/0x20
? privcmd_ioctl+0x221/0x990 [xen_privcmd]
? do_vfs_ioctl+0xa5/0x6f0
? ksys_ioctl+0x60/0x90
? trace_hardirqs_off_thunk+0x1a/0x20
? __x64_sys_ioctl+0x16/0x20
? do_syscall_64+0x62/0x250
? entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fix that by testing preempt_count() before calling cond_resched().
In kernel 5.8 this can't happen any more due to the entry code rework
(more than 100 patches, so not a candidate for backporting).
The issue was introduced in kernel 4.3, so this patch should go into
all stable kernels in [4.3 ... 5.7].
Reported-by: Sarah Newman <srn@prgmr.com>
Fixes: 0fa2f5cb2b0ecd8 ("sched/preempt, xen: Use need_resched() instead of should_resched()")
Cc: Sarah Newman <srn@prgmr.com>
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Chris Brannon <cmb@prgmr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/xen/preempt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/xen/preempt.c
+++ b/drivers/xen/preempt.c
@@ -31,7 +31,7 @@ EXPORT_SYMBOL_GPL(xen_in_preemptible_hca
asmlinkage __visible void xen_maybe_preempt_hcall(void)
{
if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
- && need_resched())) {
+ && need_resched() && !preempt_count())) {
/*
* Clear flag as we may be rescheduled on a different
* cpu.
Patches currently in stable-queue which might be from jgross@suse.com are
queue-4.14/xen-don-t-reschedule-in-preemption-off-sections.patch
This is a note to let you know that I've just added the patch titled
xen: don't reschedule in preemption off sections
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-don-t-reschedule-in-preemption-off-sections.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
From jgross@suse.com Mon Aug 24 10:12:00 2020
From: Juergen Gross <jgross@suse.com>
Date: Thu, 20 Aug 2020 08:59:08 +0200
Subject: xen: don't reschedule in preemption off sections
To: stable@vger.kernel.org
Cc: xen-devel@lists.xenproject.org, Juergen Gross <jgross@suse.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Stefano Stabellini <sstabellini@kernel.org>, Sarah Newman <srn@prgmr.com>, Chris Brannon <cmb@prgmr.com>
Message-ID: <20200820065908.20592-1-jgross@suse.com>
From: Juergen Gross <jgross@suse.com>
For support of long running hypercalls xen_maybe_preempt_hcall() is
calling cond_resched() in case a hypercall marked as preemptible has
been interrupted.
Normally this is no problem, as only hypercalls done via some ioctl()s
are marked to be preemptible. In rare cases when during such a
preemptible hypercall an interrupt occurs and any softirq action is
started from irq_exit(), a further hypercall issued by the softirq
handler will be regarded to be preemptible, too. This might lead to
rescheduling in spite of the softirq handler potentially having set
preempt_disable(), leading to splats like:
BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl
INFO: lockdep is turned off.
CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1
Call Trace:
<IRQ>
dump_stack+0x8f/0xd0
___might_sleep.cold.76+0xb2/0x103
xen_maybe_preempt_hcall+0x48/0x70
xen_do_hypervisor_callback+0x37/0x40
RIP: e030:xen_hypercall_xen_version+0xa/0x20
Code: ...
RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246
RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a
RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0
R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000
? xen_hypercall_xen_version+0xa/0x20
? xen_force_evtchn_callback+0x9/0x10
? check_events+0x12/0x20
? xen_restore_fl_direct+0x1f/0x20
? _raw_spin_unlock_irqrestore+0x53/0x60
? debug_dma_sync_single_for_cpu+0x91/0xc0
? _raw_spin_unlock_irqrestore+0x53/0x60
? xen_swiotlb_sync_single_for_cpu+0x3d/0x140
? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en]
? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en]
? net_rx_action+0x151/0x4a0
? __do_softirq+0xed/0x55b
? irq_exit+0xea/0x100
? xen_evtchn_do_upcall+0x2c/0x40
? xen_do_hypervisor_callback+0x29/0x40
</IRQ>
? xen_hypercall_domctl+0xa/0x20
? xen_hypercall_domctl+0x8/0x20
? privcmd_ioctl+0x221/0x990 [xen_privcmd]
? do_vfs_ioctl+0xa5/0x6f0
? ksys_ioctl+0x60/0x90
? trace_hardirqs_off_thunk+0x1a/0x20
? __x64_sys_ioctl+0x16/0x20
? do_syscall_64+0x62/0x250
? entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fix that by testing preempt_count() before calling cond_resched().
In kernel 5.8 this can't happen any more due to the entry code rework
(more than 100 patches, so not a candidate for backporting).
The issue was introduced in kernel 4.3, so this patch should go into
all stable kernels in [4.3 ... 5.7].
Reported-by: Sarah Newman <srn@prgmr.com>
Fixes: 0fa2f5cb2b0ecd8 ("sched/preempt, xen: Use need_resched() instead of should_resched()")
Cc: Sarah Newman <srn@prgmr.com>
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Chris Brannon <cmb@prgmr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/xen/preempt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/xen/preempt.c
+++ b/drivers/xen/preempt.c
@@ -31,7 +31,7 @@ EXPORT_SYMBOL_GPL(xen_in_preemptible_hca
asmlinkage __visible void xen_maybe_preempt_hcall(void)
{
if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
- && need_resched())) {
+ && need_resched() && !preempt_count())) {
/*
* Clear flag as we may be rescheduled on a different
* cpu.
Patches currently in stable-queue which might be from jgross@suse.com are
queue-4.19/fix-build-error-when-config_acpi-is-not-set-enabled.patch
queue-4.19/xen-don-t-reschedule-in-preemption-off-sections.patch
queue-4.19/efi-avoid-error-message-when-booting-under-xen.patch
This is a note to let you know that I've just added the patch titled
xen: don't reschedule in preemption off sections
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-don-t-reschedule-in-preemption-off-sections.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
From jgross@suse.com Mon Aug 24 10:12:00 2020
From: Juergen Gross <jgross@suse.com>
Date: Thu, 20 Aug 2020 08:59:08 +0200
Subject: xen: don't reschedule in preemption off sections
To: stable@vger.kernel.org
Cc: xen-devel@lists.xenproject.org, Juergen Gross <jgross@suse.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Stefano Stabellini <sstabellini@kernel.org>, Sarah Newman <srn@prgmr.com>, Chris Brannon <cmb@prgmr.com>
Message-ID: <20200820065908.20592-1-jgross@suse.com>
From: Juergen Gross <jgross@suse.com>
For support of long running hypercalls xen_maybe_preempt_hcall() is
calling cond_resched() in case a hypercall marked as preemptible has
been interrupted.
Normally this is no problem, as only hypercalls done via some ioctl()s
are marked to be preemptible. In rare cases when during such a
preemptible hypercall an interrupt occurs and any softirq action is
started from irq_exit(), a further hypercall issued by the softirq
handler will be regarded to be preemptible, too. This might lead to
rescheduling in spite of the softirq handler potentially having set
preempt_disable(), leading to splats like:
BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl
INFO: lockdep is turned off.
CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1
Call Trace:
<IRQ>
dump_stack+0x8f/0xd0
___might_sleep.cold.76+0xb2/0x103
xen_maybe_preempt_hcall+0x48/0x70
xen_do_hypervisor_callback+0x37/0x40
RIP: e030:xen_hypercall_xen_version+0xa/0x20
Code: ...
RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246
RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a
RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0
R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000
? xen_hypercall_xen_version+0xa/0x20
? xen_force_evtchn_callback+0x9/0x10
? check_events+0x12/0x20
? xen_restore_fl_direct+0x1f/0x20
? _raw_spin_unlock_irqrestore+0x53/0x60
? debug_dma_sync_single_for_cpu+0x91/0xc0
? _raw_spin_unlock_irqrestore+0x53/0x60
? xen_swiotlb_sync_single_for_cpu+0x3d/0x140
? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en]
? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en]
? net_rx_action+0x151/0x4a0
? __do_softirq+0xed/0x55b
? irq_exit+0xea/0x100
? xen_evtchn_do_upcall+0x2c/0x40
? xen_do_hypervisor_callback+0x29/0x40
</IRQ>
? xen_hypercall_domctl+0xa/0x20
? xen_hypercall_domctl+0x8/0x20
? privcmd_ioctl+0x221/0x990 [xen_privcmd]
? do_vfs_ioctl+0xa5/0x6f0
? ksys_ioctl+0x60/0x90
? trace_hardirqs_off_thunk+0x1a/0x20
? __x64_sys_ioctl+0x16/0x20
? do_syscall_64+0x62/0x250
? entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fix that by testing preempt_count() before calling cond_resched().
In kernel 5.8 this can't happen any more due to the entry code rework
(more than 100 patches, so not a candidate for backporting).
The issue was introduced in kernel 4.3, so this patch should go into
all stable kernels in [4.3 ... 5.7].
Reported-by: Sarah Newman <srn@prgmr.com>
Fixes: 0fa2f5cb2b0ecd8 ("sched/preempt, xen: Use need_resched() instead of should_resched()")
Cc: Sarah Newman <srn@prgmr.com>
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Chris Brannon <cmb@prgmr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/xen/preempt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/xen/preempt.c
+++ b/drivers/xen/preempt.c
@@ -27,7 +27,7 @@ EXPORT_SYMBOL_GPL(xen_in_preemptible_hca
asmlinkage __visible void xen_maybe_preempt_hcall(void)
{
if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
- && need_resched())) {
+ && need_resched() && !preempt_count())) {
/*
* Clear flag as we may be rescheduled on a different
* cpu.
Patches currently in stable-queue which might be from jgross@suse.com are
queue-5.4/fix-build-error-when-config_acpi-is-not-set-enabled.patch
queue-5.4/xen-don-t-reschedule-in-preemption-off-sections.patch
queue-5.4/efi-avoid-error-message-when-booting-under-xen.patch
queue-5.4/swiotlb-xen-use-vmalloc_to_page-on-vmalloc-virt-addr.patch
This is a note to let you know that I've just added the patch titled
xen: don't reschedule in preemption off sections
to the 5.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-don-t-reschedule-in-preemption-off-sections.patch
and it can be found in the queue-5.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
From jgross@suse.com Mon Aug 24 10:12:00 2020
From: Juergen Gross <jgross@suse.com>
Date: Thu, 20 Aug 2020 08:59:08 +0200
Subject: xen: don't reschedule in preemption off sections
To: stable@vger.kernel.org
Cc: xen-devel@lists.xenproject.org, Juergen Gross <jgross@suse.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Stefano Stabellini <sstabellini@kernel.org>, Sarah Newman <srn@prgmr.com>, Chris Brannon <cmb@prgmr.com>
Message-ID: <20200820065908.20592-1-jgross@suse.com>
From: Juergen Gross <jgross@suse.com>
For support of long running hypercalls xen_maybe_preempt_hcall() is
calling cond_resched() in case a hypercall marked as preemptible has
been interrupted.
Normally this is no problem, as only hypercalls done via some ioctl()s
are marked to be preemptible. In rare cases when during such a
preemptible hypercall an interrupt occurs and any softirq action is
started from irq_exit(), a further hypercall issued by the softirq
handler will be regarded to be preemptible, too. This might lead to
rescheduling in spite of the softirq handler potentially having set
preempt_disable(), leading to splats like:
BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl
INFO: lockdep is turned off.
CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1
Call Trace:
<IRQ>
dump_stack+0x8f/0xd0
___might_sleep.cold.76+0xb2/0x103
xen_maybe_preempt_hcall+0x48/0x70
xen_do_hypervisor_callback+0x37/0x40
RIP: e030:xen_hypercall_xen_version+0xa/0x20
Code: ...
RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246
RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a
RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0
R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000
? xen_hypercall_xen_version+0xa/0x20
? xen_force_evtchn_callback+0x9/0x10
? check_events+0x12/0x20
? xen_restore_fl_direct+0x1f/0x20
? _raw_spin_unlock_irqrestore+0x53/0x60
? debug_dma_sync_single_for_cpu+0x91/0xc0
? _raw_spin_unlock_irqrestore+0x53/0x60
? xen_swiotlb_sync_single_for_cpu+0x3d/0x140
? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en]
? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en]
? net_rx_action+0x151/0x4a0
? __do_softirq+0xed/0x55b
? irq_exit+0xea/0x100
? xen_evtchn_do_upcall+0x2c/0x40
? xen_do_hypervisor_callback+0x29/0x40
</IRQ>
? xen_hypercall_domctl+0xa/0x20
? xen_hypercall_domctl+0x8/0x20
? privcmd_ioctl+0x221/0x990 [xen_privcmd]
? do_vfs_ioctl+0xa5/0x6f0
? ksys_ioctl+0x60/0x90
? trace_hardirqs_off_thunk+0x1a/0x20
? __x64_sys_ioctl+0x16/0x20
? do_syscall_64+0x62/0x250
? entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fix that by testing preempt_count() before calling cond_resched().
In kernel 5.8 this can't happen any more due to the entry code rework
(more than 100 patches, so not a candidate for backporting).
The issue was introduced in kernel 4.3, so this patch should go into
all stable kernels in [4.3 ... 5.7].
Reported-by: Sarah Newman <srn@prgmr.com>
Fixes: 0fa2f5cb2b0ecd8 ("sched/preempt, xen: Use need_resched() instead of should_resched()")
Cc: Sarah Newman <srn@prgmr.com>
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Chris Brannon <cmb@prgmr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/xen/preempt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/xen/preempt.c
+++ b/drivers/xen/preempt.c
@@ -27,7 +27,7 @@ EXPORT_SYMBOL_GPL(xen_in_preemptible_hca
asmlinkage __visible void xen_maybe_preempt_hcall(void)
{
if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
- && need_resched())) {
+ && need_resched() && !preempt_count())) {
/*
* Clear flag as we may be rescheduled on a different
* cpu.
Patches currently in stable-queue which might be from jgross@suse.com are
queue-5.7/fix-build-error-when-config_acpi-is-not-set-enabled.patch
queue-5.7/xen-don-t-reschedule-in-preemption-off-sections.patch
queue-5.7/efi-avoid-error-message-when-booting-under-xen.patch
queue-5.7/swiotlb-xen-use-vmalloc_to_page-on-vmalloc-virt-addr.patch
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