* [PATCH] x86, mm: only wait for flushes from online cpus
@ 2012-06-20 22:03 mandeep.baines
2012-07-18 21:05 ` Srivatsa S. Bhat
0 siblings, 1 reply; 3+ messages in thread
From: mandeep.baines @ 2012-06-20 22:03 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, linux-kernel
Cc: Mandeep Singh Baines, x86, Tejun Heo, Andrew Morton,
Stephen Rothwell, Christoph Lameter, Olof Johansson
From: Mandeep Singh Baines <msb@chromium.org>
A cpu in the mm_cpumask could go offline before we send the
invalidate IPI causing us to wait forever.
Bug Trace:
<4>[10222.234548] WARNING: at ../../arch/x86/kernel/apic/ipi.c:113 default_send_IPI_mask_logical+0x58/0x73()
<5>[10222.234633] Pid: 23605, comm: lmt-udev Tainted: G C 3.2.7 #1
<5>[10222.234639] Call Trace:
<5>[10222.234651] [<8102e666>] warn_slowpath_common+0x68/0x7d
<5>[10222.234661] [<81016c36>] ? default_send_IPI_mask_logical+0x58/0x73
<5>[10222.234670] [<8102e68f>] warn_slowpath_null+0x14/0x18
<5>[10222.234678] [<81016c36>] default_send_IPI_mask_logical+0x58/0x73
<5>[10222.234687] [<8101eec2>] flush_tlb_others_ipi+0x86/0xba
<5>[10222.234696] [<8101f0bb>] flush_tlb_mm+0x5e/0x62
<5>[10222.234703] [<8101e36c>] pud_populate+0x2c/0x31
<5>[10222.234711] [<8101e409>] pgd_alloc+0x98/0xc7
<5>[10222.234719] [<8102c881>] mm_init.isra.38+0xcc/0xf3
<5>[10222.234727] [<8102cbc2>] dup_mm+0x68/0x34e
<5>[10222.234736] [<8139bbae>] ? _cond_resched+0xd/0x21
<5>[10222.234745] [<810a5b7c>] ? kmem_cache_alloc+0x26/0xe2
<5>[10222.234753] [<8102d421>] ? copy_process+0x556/0xda6
<5>[10222.234761] [<8102d641>] copy_process+0x776/0xda6
<5>[10222.234770] [<8102dd5e>] do_fork+0xcb/0x1d4
<5>[10222.234778] [<810a8c96>] ? do_sync_write+0xd3/0xd3
<5>[10222.234786] [<810a94ab>] ? vfs_read+0x95/0xa2
<5>[10222.234795] [<81008850>] sys_clone+0x20/0x25
<5>[10222.234804] [<8139d8c5>] ptregs_clone+0x15/0x30
<5>[10222.234812] [<8139d7f7>] ? sysenter_do_call+0x12/0x26
<4>[10222.234818] ---[ end trace 31e095600f50fd48 ]---
<3>[10234.880183] BUG: soft lockup - CPU#0 stuck for 11s! [lmt-udev:23605]
Addresses http://crosbug.com/31737
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Christoph Lameter <cl@gentwo.org>
Cc: Olof Johansson <olofj@chromium.org>
---
arch/x86/mm/tlb.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 5e57e11..010090d 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -194,8 +194,13 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
apic->send_IPI_mask(to_cpumask(f->flush_cpumask),
INVALIDATE_TLB_VECTOR_START + sender);
- while (!cpumask_empty(to_cpumask(f->flush_cpumask)))
+ while (!cpumask_empty(to_cpumask(f->flush_cpumask))) {
+ /* Only wait for online cpus */
+ cpumask_and(to_cpumask(f->flush_cpumask),
+ to_cpumask(f->flush_cpumask),
+ cpu_online_mask);
cpu_relax();
+ }
}
f->flush_mm = NULL;
--
1.7.3.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] x86, mm: only wait for flushes from online cpus
2012-06-20 22:03 [PATCH] x86, mm: only wait for flushes from online cpus mandeep.baines
@ 2012-07-18 21:05 ` Srivatsa S. Bhat
2012-07-18 22:09 ` Mandeep Singh Baines
0 siblings, 1 reply; 3+ messages in thread
From: Srivatsa S. Bhat @ 2012-07-18 21:05 UTC (permalink / raw)
To: mandeep.baines
Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, linux-kernel,
Mandeep Singh Baines, x86, Tejun Heo, Andrew Morton,
Stephen Rothwell, Christoph Lameter, Olof Johansson
On 06/21/2012 03:33 AM, mandeep.baines@gmail.com wrote:
> From: Mandeep Singh Baines <msb@chromium.org>
>
> A cpu in the mm_cpumask could go offline before we send the
> invalidate IPI causing us to wait forever.
>
> Bug Trace:
>
> <4>[10222.234548] WARNING: at ../../arch/x86/kernel/apic/ipi.c:113 default_send_IPI_mask_logical+0x58/0x73()
> <5>[10222.234633] Pid: 23605, comm: lmt-udev Tainted: G C 3.2.7 #1
> <5>[10222.234639] Call Trace:
> <5>[10222.234651] [<8102e666>] warn_slowpath_common+0x68/0x7d
> <5>[10222.234661] [<81016c36>] ? default_send_IPI_mask_logical+0x58/0x73
> <5>[10222.234670] [<8102e68f>] warn_slowpath_null+0x14/0x18
> <5>[10222.234678] [<81016c36>] default_send_IPI_mask_logical+0x58/0x73
> <5>[10222.234687] [<8101eec2>] flush_tlb_others_ipi+0x86/0xba
> <5>[10222.234696] [<8101f0bb>] flush_tlb_mm+0x5e/0x62
> <5>[10222.234703] [<8101e36c>] pud_populate+0x2c/0x31
> <5>[10222.234711] [<8101e409>] pgd_alloc+0x98/0xc7
> <5>[10222.234719] [<8102c881>] mm_init.isra.38+0xcc/0xf3
> <5>[10222.234727] [<8102cbc2>] dup_mm+0x68/0x34e
> <5>[10222.234736] [<8139bbae>] ? _cond_resched+0xd/0x21
> <5>[10222.234745] [<810a5b7c>] ? kmem_cache_alloc+0x26/0xe2
> <5>[10222.234753] [<8102d421>] ? copy_process+0x556/0xda6
> <5>[10222.234761] [<8102d641>] copy_process+0x776/0xda6
> <5>[10222.234770] [<8102dd5e>] do_fork+0xcb/0x1d4
> <5>[10222.234778] [<810a8c96>] ? do_sync_write+0xd3/0xd3
> <5>[10222.234786] [<810a94ab>] ? vfs_read+0x95/0xa2
> <5>[10222.234795] [<81008850>] sys_clone+0x20/0x25
> <5>[10222.234804] [<8139d8c5>] ptregs_clone+0x15/0x30
> <5>[10222.234812] [<8139d7f7>] ? sysenter_do_call+0x12/0x26
> <4>[10222.234818] ---[ end trace 31e095600f50fd48 ]---
> <3>[10234.880183] BUG: soft lockup - CPU#0 stuck for 11s! [lmt-udev:23605]
>
> Addresses http://crosbug.com/31737
>
> Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: x86@kernel.org
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Cc: Christoph Lameter <cl@gentwo.org>
> Cc: Olof Johansson <olofj@chromium.org>
> ---
> arch/x86/mm/tlb.c | 7 ++++++-
> 1 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index 5e57e11..010090d 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -194,8 +194,13 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
> apic->send_IPI_mask(to_cpumask(f->flush_cpumask),
> INVALIDATE_TLB_VECTOR_START + sender);
>
This function is always called with preempt_disabled() right?
In that case, _while_ this function is running, a CPU cannot go offline
because of stop_machine(). (I understand that it might go offline in between
calculating that cpumask and calling preempt_disable() - which is the race
you are trying to handle).
So, why not take the offline cpus out of the way even before sending that IPI?
That way, we need not modify the while loop below.
> - while (!cpumask_empty(to_cpumask(f->flush_cpumask)))
> + while (!cpumask_empty(to_cpumask(f->flush_cpumask))) {
> + /* Only wait for online cpus */
> + cpumask_and(to_cpumask(f->flush_cpumask),
> + to_cpumask(f->flush_cpumask),
> + cpu_online_mask);
> cpu_relax();
> + }
> }
>
> f->flush_mm = NULL;
>
That is, how about something like this:
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 5e57e11..9d387a9 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -186,7 +186,11 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
f->flush_mm = mm;
f->flush_va = va;
- if (cpumask_andnot(to_cpumask(f->flush_cpumask), cpumask, cpumask_of(smp_processor_id()))) {
+
+ cpumask_and(to_cpumask(f->flush_cpumask), cpumask, cpu_online_mask);
+ cpumask_clear_cpu(smp_processor_id(), to_cpumask(f->flush_cpumask));
+
+ if (!cpumask_empty(to_cpumask(f->flush_cpumask))) {
/*
* We have to send the IPI only to
* CPUs affected.
Regards,
Srivatsa S. Bhat
IBM Linux Technology Center
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] x86, mm: only wait for flushes from online cpus
2012-07-18 21:05 ` Srivatsa S. Bhat
@ 2012-07-18 22:09 ` Mandeep Singh Baines
0 siblings, 0 replies; 3+ messages in thread
From: Mandeep Singh Baines @ 2012-07-18 22:09 UTC (permalink / raw)
To: Srivatsa S. Bhat
Cc: mandeep.baines, Thomas Gleixner, Ingo Molnar, H. Peter Anvin,
linux-kernel, Mandeep Singh Baines, x86, Tejun Heo,
Andrew Morton, Stephen Rothwell, Christoph Lameter,
Olof Johansson
Srivatsa S. Bhat (srivatsa.bhat@linux.vnet.ibm.com) wrote:
> On 06/21/2012 03:33 AM, mandeep.baines@gmail.com wrote:
> > From: Mandeep Singh Baines <msb@chromium.org>
> >
> > A cpu in the mm_cpumask could go offline before we send the
> > invalidate IPI causing us to wait forever.
> >
> > Bug Trace:
> >
> > <4>[10222.234548] WARNING: at ../../arch/x86/kernel/apic/ipi.c:113 default_send_IPI_mask_logical+0x58/0x73()
> > <5>[10222.234633] Pid: 23605, comm: lmt-udev Tainted: G C 3.2.7 #1
> > <5>[10222.234639] Call Trace:
> > <5>[10222.234651] [<8102e666>] warn_slowpath_common+0x68/0x7d
> > <5>[10222.234661] [<81016c36>] ? default_send_IPI_mask_logical+0x58/0x73
> > <5>[10222.234670] [<8102e68f>] warn_slowpath_null+0x14/0x18
> > <5>[10222.234678] [<81016c36>] default_send_IPI_mask_logical+0x58/0x73
> > <5>[10222.234687] [<8101eec2>] flush_tlb_others_ipi+0x86/0xba
> > <5>[10222.234696] [<8101f0bb>] flush_tlb_mm+0x5e/0x62
> > <5>[10222.234703] [<8101e36c>] pud_populate+0x2c/0x31
> > <5>[10222.234711] [<8101e409>] pgd_alloc+0x98/0xc7
> > <5>[10222.234719] [<8102c881>] mm_init.isra.38+0xcc/0xf3
> > <5>[10222.234727] [<8102cbc2>] dup_mm+0x68/0x34e
> > <5>[10222.234736] [<8139bbae>] ? _cond_resched+0xd/0x21
> > <5>[10222.234745] [<810a5b7c>] ? kmem_cache_alloc+0x26/0xe2
> > <5>[10222.234753] [<8102d421>] ? copy_process+0x556/0xda6
> > <5>[10222.234761] [<8102d641>] copy_process+0x776/0xda6
> > <5>[10222.234770] [<8102dd5e>] do_fork+0xcb/0x1d4
> > <5>[10222.234778] [<810a8c96>] ? do_sync_write+0xd3/0xd3
> > <5>[10222.234786] [<810a94ab>] ? vfs_read+0x95/0xa2
> > <5>[10222.234795] [<81008850>] sys_clone+0x20/0x25
> > <5>[10222.234804] [<8139d8c5>] ptregs_clone+0x15/0x30
> > <5>[10222.234812] [<8139d7f7>] ? sysenter_do_call+0x12/0x26
> > <4>[10222.234818] ---[ end trace 31e095600f50fd48 ]---
> > <3>[10234.880183] BUG: soft lockup - CPU#0 stuck for 11s! [lmt-udev:23605]
> >
> > Addresses http://crosbug.com/31737
> >
> > Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: x86@kernel.org
> > Cc: Tejun Heo <tj@kernel.org>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> > Cc: Christoph Lameter <cl@gentwo.org>
> > Cc: Olof Johansson <olofj@chromium.org>
> > ---
> > arch/x86/mm/tlb.c | 7 ++++++-
> > 1 files changed, 6 insertions(+), 1 deletions(-)
> >
> > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> > index 5e57e11..010090d 100644
> > --- a/arch/x86/mm/tlb.c
> > +++ b/arch/x86/mm/tlb.c
> > @@ -194,8 +194,13 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
> > apic->send_IPI_mask(to_cpumask(f->flush_cpumask),
> > INVALIDATE_TLB_VECTOR_START + sender);
> >
>
> This function is always called with preempt_disabled() right?
> In that case, _while_ this function is running, a CPU cannot go offline
> because of stop_machine(). (I understand that it might go offline in between
> calculating that cpumask and calling preempt_disable() - which is the race
> you are trying to handle).
>
Ah. Good point. A cpu cannot be remove from the cpu_online_mask while
preemption is disabled because stop_machine() can't run until
preemption is enabled.
./kernel/cpu.c: err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
> So, why not take the offline cpus out of the way even before sending that IPI?
> That way, we need not modify the while loop below.
>
> > - while (!cpumask_empty(to_cpumask(f->flush_cpumask)))
> > + while (!cpumask_empty(to_cpumask(f->flush_cpumask))) {
> > + /* Only wait for online cpus */
> > + cpumask_and(to_cpumask(f->flush_cpumask),
> > + to_cpumask(f->flush_cpumask),
> > + cpu_online_mask);
> > cpu_relax();
> > + }
> > }
> >
> > f->flush_mm = NULL;
> >
>
> That is, how about something like this:
>
Acked-off-by: Mandeep Singh Baines <msb@chromium.org>
Do you mind re-sending you're patch with a proper sign-off.
Thanks and regards,
Mandeep
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index 5e57e11..9d387a9 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -186,7 +186,11 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
>
> f->flush_mm = mm;
> f->flush_va = va;
> - if (cpumask_andnot(to_cpumask(f->flush_cpumask), cpumask, cpumask_of(smp_processor_id()))) {
> +
> + cpumask_and(to_cpumask(f->flush_cpumask), cpumask, cpu_online_mask);
> + cpumask_clear_cpu(smp_processor_id(), to_cpumask(f->flush_cpumask));
> +
> + if (!cpumask_empty(to_cpumask(f->flush_cpumask))) {
> /*
> * We have to send the IPI only to
> * CPUs affected.
>
>
>
> Regards,
> Srivatsa S. Bhat
> IBM Linux Technology Center
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2012-07-18 22:09 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2012-06-20 22:03 [PATCH] x86, mm: only wait for flushes from online cpus mandeep.baines
2012-07-18 21:05 ` Srivatsa S. Bhat
2012-07-18 22:09 ` Mandeep Singh Baines
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