From: zhong jiang <[email protected]>
A soft lookup will occur when I run trinity in syscall kexec_load.
the corresponding stack information is as follows.
[ 237.235937] BUG: soft lockup - CPU#6 stuck for 22s! [trinity-c6:13859]
[ 237.242699] Kernel panic - not syncing: softlockup: hung tasks
[ 237.248573] CPU: 6 PID: 13859 Comm: trinity-c6 Tainted: G O L ----V------- 3.10.0-327.28.3.35.zhongjiang.x86_64 #1
[ 237.259984] Hardware name: Huawei Technologies Co., Ltd. Tecal BH622 V2/BC01SRSA0, BIOS RMIBV386 06/30/2014
[ 237.269752] ffffffff8187626b 0000000018cfde31 ffff88184c803e18 ffffffff81638f16
[ 237.277471] ffff88184c803e98 ffffffff8163278f 0000000000000008 ffff88184c803ea8
[ 237.285190] ffff88184c803e48 0000000018cfde31 ffff88184c803e67 0000000000000000
[ 237.292909] Call Trace:
[ 237.295404] <IRQ> [<ffffffff81638f16>] dump_stack+0x19/0x1b
[ 237.301352] [<ffffffff8163278f>] panic+0xd8/0x214
[ 237.306196] [<ffffffff8111d6fc>] watchdog_timer_fn+0x1cc/0x1e0
[ 237.312157] [<ffffffff8111d530>] ? watchdog_enable+0xc0/0xc0
[ 237.317955] [<ffffffff810aa182>] __hrtimer_run_queues+0xd2/0x260
[ 237.324087] [<ffffffff810aa720>] hrtimer_interrupt+0xb0/0x1e0
[ 237.329963] [<ffffffff8164ae5c>] ? call_softirq+0x1c/0x30
[ 237.335500] [<ffffffff81049a77>] local_apic_timer_interrupt+0x37/0x60
[ 237.342228] [<ffffffff8164bacf>] smp_apic_timer_interrupt+0x3f/0x60
[ 237.348771] [<ffffffff8164a11d>] apic_timer_interrupt+0x6d/0x80
[ 237.354967] <EOI> [<ffffffff810f3a00>] ? kimage_alloc_control_pages+0x80/0x270
[ 237.362875] [<ffffffff811c3ebe>] ? kmem_cache_alloc_trace+0x1ce/0x1f0
[ 237.369592] [<ffffffff810f362f>] ? do_kimage_alloc_init+0x1f/0x90
[ 237.375992] [<ffffffff810f3d1a>] kimage_alloc_init+0x12a/0x180
[ 237.382103] [<ffffffff810f3f9a>] SyS_kexec_load+0x20a/0x260
[ 237.387957] [<ffffffff816494c9>] system_call_fastpath+0x16/0x1b
the first time allocate control pages may take too much time because
crash_res.end can be set to a higher value. we need to add cond_resched
to avoid the issue.
The patch have been tested and above issue is not appear.
Signed-off-by: zhong jiang <[email protected]>
---
kernel/kexec_core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 5616755..bfc9621 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -441,6 +441,8 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
while (hole_end <= crashk_res.end) {
unsigned long i;
+ cond_resched();
+
if (hole_end > KEXEC_CRASH_CONTROL_MEMORY_LIMIT)
break;
/* See if I overlap any of the segments */
--
1.8.3.1
zhongjiang <[email protected]> writes:
> From: zhong jiang <[email protected]>
>
> A soft lookup will occur when I run trinity in syscall kexec_load.
> the corresponding stack information is as follows.
Acked-by: "Eric W. Biederman" <[email protected]>
>
> [ 237.235937] BUG: soft lockup - CPU#6 stuck for 22s! [trinity-c6:13859]
> [ 237.242699] Kernel panic - not syncing: softlockup: hung tasks
> [ 237.248573] CPU: 6 PID: 13859 Comm: trinity-c6 Tainted: G O L ----V------- 3.10.0-327.28.3.35.zhongjiang.x86_64 #1
> [ 237.259984] Hardware name: Huawei Technologies Co., Ltd. Tecal BH622 V2/BC01SRSA0, BIOS RMIBV386 06/30/2014
> [ 237.269752] ffffffff8187626b 0000000018cfde31 ffff88184c803e18 ffffffff81638f16
> [ 237.277471] ffff88184c803e98 ffffffff8163278f 0000000000000008 ffff88184c803ea8
> [ 237.285190] ffff88184c803e48 0000000018cfde31 ffff88184c803e67 0000000000000000
> [ 237.292909] Call Trace:
> [ 237.295404] <IRQ> [<ffffffff81638f16>] dump_stack+0x19/0x1b
> [ 237.301352] [<ffffffff8163278f>] panic+0xd8/0x214
> [ 237.306196] [<ffffffff8111d6fc>] watchdog_timer_fn+0x1cc/0x1e0
> [ 237.312157] [<ffffffff8111d530>] ? watchdog_enable+0xc0/0xc0
> [ 237.317955] [<ffffffff810aa182>] __hrtimer_run_queues+0xd2/0x260
> [ 237.324087] [<ffffffff810aa720>] hrtimer_interrupt+0xb0/0x1e0
> [ 237.329963] [<ffffffff8164ae5c>] ? call_softirq+0x1c/0x30
> [ 237.335500] [<ffffffff81049a77>] local_apic_timer_interrupt+0x37/0x60
> [ 237.342228] [<ffffffff8164bacf>] smp_apic_timer_interrupt+0x3f/0x60
> [ 237.348771] [<ffffffff8164a11d>] apic_timer_interrupt+0x6d/0x80
> [ 237.354967] <EOI> [<ffffffff810f3a00>] ? kimage_alloc_control_pages+0x80/0x270
> [ 237.362875] [<ffffffff811c3ebe>] ? kmem_cache_alloc_trace+0x1ce/0x1f0
> [ 237.369592] [<ffffffff810f362f>] ? do_kimage_alloc_init+0x1f/0x90
> [ 237.375992] [<ffffffff810f3d1a>] kimage_alloc_init+0x12a/0x180
> [ 237.382103] [<ffffffff810f3f9a>] SyS_kexec_load+0x20a/0x260
> [ 237.387957] [<ffffffff816494c9>] system_call_fastpath+0x16/0x1b
>
> the first time allocate control pages may take too much time because
> crash_res.end can be set to a higher value. we need to add cond_resched
> to avoid the issue.
>
> The patch have been tested and above issue is not appear.
>
> Signed-off-by: zhong jiang <[email protected]>
> ---
> kernel/kexec_core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 5616755..bfc9621 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -441,6 +441,8 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
> while (hole_end <= crashk_res.end) {
> unsigned long i;
>
> + cond_resched();
> +
> if (hole_end > KEXEC_CRASH_CONTROL_MEMORY_LIMIT)
> break;
> /* See if I overlap any of the segments */
On 12/08/2016 at 10:37 AM, zhongjiang wrote:
> From: zhong jiang <[email protected]>
>
> A soft lookup will occur when I run trinity in syscall kexec_load.
> the corresponding stack information is as follows.
>
> [ 237.235937] BUG: soft lockup - CPU#6 stuck for 22s! [trinity-c6:13859]
> [ 237.242699] Kernel panic - not syncing: softlockup: hung tasks
> [ 237.248573] CPU: 6 PID: 13859 Comm: trinity-c6 Tainted: G O L ----V------- 3.10.0-327.28.3.35.zhongjiang.x86_64 #1
> [ 237.259984] Hardware name: Huawei Technologies Co., Ltd. Tecal BH622 V2/BC01SRSA0, BIOS RMIBV386 06/30/2014
> [ 237.269752] ffffffff8187626b 0000000018cfde31 ffff88184c803e18 ffffffff81638f16
> [ 237.277471] ffff88184c803e98 ffffffff8163278f 0000000000000008 ffff88184c803ea8
> [ 237.285190] ffff88184c803e48 0000000018cfde31 ffff88184c803e67 0000000000000000
> [ 237.292909] Call Trace:
> [ 237.295404] <IRQ> [<ffffffff81638f16>] dump_stack+0x19/0x1b
> [ 237.301352] [<ffffffff8163278f>] panic+0xd8/0x214
> [ 237.306196] [<ffffffff8111d6fc>] watchdog_timer_fn+0x1cc/0x1e0
> [ 237.312157] [<ffffffff8111d530>] ? watchdog_enable+0xc0/0xc0
> [ 237.317955] [<ffffffff810aa182>] __hrtimer_run_queues+0xd2/0x260
> [ 237.324087] [<ffffffff810aa720>] hrtimer_interrupt+0xb0/0x1e0
> [ 237.329963] [<ffffffff8164ae5c>] ? call_softirq+0x1c/0x30
> [ 237.335500] [<ffffffff81049a77>] local_apic_timer_interrupt+0x37/0x60
> [ 237.342228] [<ffffffff8164bacf>] smp_apic_timer_interrupt+0x3f/0x60
> [ 237.348771] [<ffffffff8164a11d>] apic_timer_interrupt+0x6d/0x80
> [ 237.354967] <EOI> [<ffffffff810f3a00>] ? kimage_alloc_control_pages+0x80/0x270
> [ 237.362875] [<ffffffff811c3ebe>] ? kmem_cache_alloc_trace+0x1ce/0x1f0
> [ 237.369592] [<ffffffff810f362f>] ? do_kimage_alloc_init+0x1f/0x90
> [ 237.375992] [<ffffffff810f3d1a>] kimage_alloc_init+0x12a/0x180
> [ 237.382103] [<ffffffff810f3f9a>] SyS_kexec_load+0x20a/0x260
> [ 237.387957] [<ffffffff816494c9>] system_call_fastpath+0x16/0x1b
>
> the first time allocate control pages may take too much time because
> crash_res.end can be set to a higher value. we need to add cond_resched
> to avoid the issue.
>
> The patch have been tested and above issue is not appear.
>
> Signed-off-by: zhong jiang <[email protected]>
> ---
> kernel/kexec_core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 5616755..bfc9621 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -441,6 +441,8 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
> while (hole_end <= crashk_res.end) {
> unsigned long i;
>
> + cond_resched();
> +
I can't see why it would take a long time to loop inside, the job it does is simply to find a control area
not overlapped with image->segment[], you can see the loop "for (i = 0; i < image->nr_segments; i++)",
@hole_end will be advanced to the end of its next nearby segment once overlap was detected each loop,
also there are limited (<=16) segments, so it won't take long to locate the right area.
Am I missing something?
Regards,
Xunlei
> if (hole_end > KEXEC_CRASH_CONTROL_MEMORY_LIMIT)
> break;
> /* See if I overlap any of the segments */
On 2016/12/8 17:41, Xunlei Pang wrote:
> On 12/08/2016 at 10:37 AM, zhongjiang wrote:
>> From: zhong jiang <[email protected]>
>>
>> A soft lookup will occur when I run trinity in syscall kexec_load.
>> the corresponding stack information is as follows.
>>
>> [ 237.235937] BUG: soft lockup - CPU#6 stuck for 22s! [trinity-c6:13859]
>> [ 237.242699] Kernel panic - not syncing: softlockup: hung tasks
>> [ 237.248573] CPU: 6 PID: 13859 Comm: trinity-c6 Tainted: G O L ----V------- 3.10.0-327.28.3.35.zhongjiang.x86_64 #1
>> [ 237.259984] Hardware name: Huawei Technologies Co., Ltd. Tecal BH622 V2/BC01SRSA0, BIOS RMIBV386 06/30/2014
>> [ 237.269752] ffffffff8187626b 0000000018cfde31 ffff88184c803e18 ffffffff81638f16
>> [ 237.277471] ffff88184c803e98 ffffffff8163278f 0000000000000008 ffff88184c803ea8
>> [ 237.285190] ffff88184c803e48 0000000018cfde31 ffff88184c803e67 0000000000000000
>> [ 237.292909] Call Trace:
>> [ 237.295404] <IRQ> [<ffffffff81638f16>] dump_stack+0x19/0x1b
>> [ 237.301352] [<ffffffff8163278f>] panic+0xd8/0x214
>> [ 237.306196] [<ffffffff8111d6fc>] watchdog_timer_fn+0x1cc/0x1e0
>> [ 237.312157] [<ffffffff8111d530>] ? watchdog_enable+0xc0/0xc0
>> [ 237.317955] [<ffffffff810aa182>] __hrtimer_run_queues+0xd2/0x260
>> [ 237.324087] [<ffffffff810aa720>] hrtimer_interrupt+0xb0/0x1e0
>> [ 237.329963] [<ffffffff8164ae5c>] ? call_softirq+0x1c/0x30
>> [ 237.335500] [<ffffffff81049a77>] local_apic_timer_interrupt+0x37/0x60
>> [ 237.342228] [<ffffffff8164bacf>] smp_apic_timer_interrupt+0x3f/0x60
>> [ 237.348771] [<ffffffff8164a11d>] apic_timer_interrupt+0x6d/0x80
>> [ 237.354967] <EOI> [<ffffffff810f3a00>] ? kimage_alloc_control_pages+0x80/0x270
>> [ 237.362875] [<ffffffff811c3ebe>] ? kmem_cache_alloc_trace+0x1ce/0x1f0
>> [ 237.369592] [<ffffffff810f362f>] ? do_kimage_alloc_init+0x1f/0x90
>> [ 237.375992] [<ffffffff810f3d1a>] kimage_alloc_init+0x12a/0x180
>> [ 237.382103] [<ffffffff810f3f9a>] SyS_kexec_load+0x20a/0x260
>> [ 237.387957] [<ffffffff816494c9>] system_call_fastpath+0x16/0x1b
>>
>> the first time allocate control pages may take too much time because
>> crash_res.end can be set to a higher value. we need to add cond_resched
>> to avoid the issue.
>>
>> The patch have been tested and above issue is not appear.
>>
>> Signed-off-by: zhong jiang <[email protected]>
>> ---
>> kernel/kexec_core.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>> index 5616755..bfc9621 100644
>> --- a/kernel/kexec_core.c
>> +++ b/kernel/kexec_core.c
>> @@ -441,6 +441,8 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
>> while (hole_end <= crashk_res.end) {
>> unsigned long i;
>>
>> + cond_resched();
>> +
> I can't see why it would take a long time to loop inside, the job it does is simply to find a control area
> not overlapped with image->segment[], you can see the loop "for (i = 0; i < image->nr_segments; i++)",
> @hole_end will be advanced to the end of its next nearby segment once overlap was detected each loop,
> also there are limited (<=16) segments, so it won't take long to locate the right area.
>
> Am I missing something?
>
> Regards,
> Xunlei
if the crashkernel = auto is set in cmdline. it represent crashk_res.end will exceed to 4G, the first allocate control pages will
loop million times. if we set crashk_res.end to the higher value manually, you can image....
Thanks
zhongjiang
>> if (hole_end > KEXEC_CRASH_CONTROL_MEMORY_LIMIT)
>> break;
>> /* See if I overlap any of the segments */
>
> .
>
zhong jiang <[email protected]> writes:
> On 2016/12/8 17:41, Xunlei Pang wrote:
>> On 12/08/2016 at 10:37 AM, zhongjiang wrote:
>>> From: zhong jiang <[email protected]>
>>>
[snip]
>>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>>> index 5616755..bfc9621 100644
>>> --- a/kernel/kexec_core.c
>>> +++ b/kernel/kexec_core.c
>>> @@ -441,6 +441,8 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
>>> while (hole_end <= crashk_res.end) {
>>> unsigned long i;
>>>
>>> + cond_resched();
>>> +
>> I can't see why it would take a long time to loop inside, the job it does is simply to find a control area
>> not overlapped with image->segment[], you can see the loop "for (i = 0; i < image->nr_segments; i++)",
>> @hole_end will be advanced to the end of its next nearby segment once overlap was detected each loop,
>> also there are limited (<=16) segments, so it won't take long to locate the right area.
>>
>> Am I missing something?
>>
>> Regards,
>> Xunlei
> if the crashkernel = auto is set in cmdline. it represent crashk_res.end will exceed to 4G, the first allocate control pages will
> loop million times. if we set crashk_res.end to the higher value
> manually, you can image....
Or in short the cond_resched is about keeping things reasonable when the
loop has worst case behavior.
Eric
On 2016/12/9 13:19, Eric W. Biederman wrote:
> zhong jiang <[email protected]> writes:
>
>> On 2016/12/8 17:41, Xunlei Pang wrote:
>>> On 12/08/2016 at 10:37 AM, zhongjiang wrote:
>>>> From: zhong jiang <[email protected]>
>>>>
> [snip]
>>>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>>>> index 5616755..bfc9621 100644
>>>> --- a/kernel/kexec_core.c
>>>> +++ b/kernel/kexec_core.c
>>>> @@ -441,6 +441,8 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
>>>> while (hole_end <= crashk_res.end) {
>>>> unsigned long i;
>>>>
>>>> + cond_resched();
>>>> +
>>> I can't see why it would take a long time to loop inside, the job it does is simply to find a control area
>>> not overlapped with image->segment[], you can see the loop "for (i = 0; i < image->nr_segments; i++)",
>>> @hole_end will be advanced to the end of its next nearby segment once overlap was detected each loop,
>>> also there are limited (<=16) segments, so it won't take long to locate the right area.
>>>
>>> Am I missing something?
>>>
>>> Regards,
>>> Xunlei
>> if the crashkernel = auto is set in cmdline. it represent crashk_res.end will exceed to 4G, the first allocate control pages will
>> loop million times. if we set crashk_res.end to the higher value
>> manually, you can image....
> Or in short the cond_resched is about keeping things reasonable when the
> loop has worst case behavior.
>
> Eric
>
>
Yes, Thank you reply and comment.
Regards,
zhongjiang
On 12/09/2016 at 01:13 PM, zhong jiang wrote:
> On 2016/12/8 17:41, Xunlei Pang wrote:
>> On 12/08/2016 at 10:37 AM, zhongjiang wrote:
>>> From: zhong jiang <[email protected]>
>>>
>>> A soft lookup will occur when I run trinity in syscall kexec_load.
>>> the corresponding stack information is as follows.
>>>
>>> [ 237.235937] BUG: soft lockup - CPU#6 stuck for 22s! [trinity-c6:13859]
>>> [ 237.242699] Kernel panic - not syncing: softlockup: hung tasks
>>> [ 237.248573] CPU: 6 PID: 13859 Comm: trinity-c6 Tainted: G O L ----V------- 3.10.0-327.28.3.35.zhongjiang.x86_64 #1
>>> [ 237.259984] Hardware name: Huawei Technologies Co., Ltd. Tecal BH622 V2/BC01SRSA0, BIOS RMIBV386 06/30/2014
>>> [ 237.269752] ffffffff8187626b 0000000018cfde31 ffff88184c803e18 ffffffff81638f16
>>> [ 237.277471] ffff88184c803e98 ffffffff8163278f 0000000000000008 ffff88184c803ea8
>>> [ 237.285190] ffff88184c803e48 0000000018cfde31 ffff88184c803e67 0000000000000000
>>> [ 237.292909] Call Trace:
>>> [ 237.295404] <IRQ> [<ffffffff81638f16>] dump_stack+0x19/0x1b
>>> [ 237.301352] [<ffffffff8163278f>] panic+0xd8/0x214
>>> [ 237.306196] [<ffffffff8111d6fc>] watchdog_timer_fn+0x1cc/0x1e0
>>> [ 237.312157] [<ffffffff8111d530>] ? watchdog_enable+0xc0/0xc0
>>> [ 237.317955] [<ffffffff810aa182>] __hrtimer_run_queues+0xd2/0x260
>>> [ 237.324087] [<ffffffff810aa720>] hrtimer_interrupt+0xb0/0x1e0
>>> [ 237.329963] [<ffffffff8164ae5c>] ? call_softirq+0x1c/0x30
>>> [ 237.335500] [<ffffffff81049a77>] local_apic_timer_interrupt+0x37/0x60
>>> [ 237.342228] [<ffffffff8164bacf>] smp_apic_timer_interrupt+0x3f/0x60
>>> [ 237.348771] [<ffffffff8164a11d>] apic_timer_interrupt+0x6d/0x80
>>> [ 237.354967] <EOI> [<ffffffff810f3a00>] ? kimage_alloc_control_pages+0x80/0x270
>>> [ 237.362875] [<ffffffff811c3ebe>] ? kmem_cache_alloc_trace+0x1ce/0x1f0
>>> [ 237.369592] [<ffffffff810f362f>] ? do_kimage_alloc_init+0x1f/0x90
>>> [ 237.375992] [<ffffffff810f3d1a>] kimage_alloc_init+0x12a/0x180
>>> [ 237.382103] [<ffffffff810f3f9a>] SyS_kexec_load+0x20a/0x260
>>> [ 237.387957] [<ffffffff816494c9>] system_call_fastpath+0x16/0x1b
>>>
>>> the first time allocate control pages may take too much time because
>>> crash_res.end can be set to a higher value. we need to add cond_resched
>>> to avoid the issue.
>>>
>>> The patch have been tested and above issue is not appear.
>>>
>>> Signed-off-by: zhong jiang <[email protected]>
>>> ---
>>> kernel/kexec_core.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>>> index 5616755..bfc9621 100644
>>> --- a/kernel/kexec_core.c
>>> +++ b/kernel/kexec_core.c
>>> @@ -441,6 +441,8 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
>>> while (hole_end <= crashk_res.end) {
>>> unsigned long i;
>>>
>>> + cond_resched();
>>> +
>> I can't see why it would take a long time to loop inside, the job it does is simply to find a control area
>> not overlapped with image->segment[], you can see the loop "for (i = 0; i < image->nr_segments; i++)",
>> @hole_end will be advanced to the end of its next nearby segment once overlap was detected each loop,
>> also there are limited (<=16) segments, so it won't take long to locate the right area.
>>
>> Am I missing something?
>>
>> Regards,
>> Xunlei
> if the crashkernel = auto is set in cmdline. it represent crashk_res.end will exceed to 4G, the first allocate control pages will
> loop million times. if we set crashk_res.end to the higher value manually, you can image....
How does "loop million times" happen? See my inlined comments prefixed with "pxl".
kimage_alloc_crash_control_pages():
while (hole_end <= crashk_res.end) {
unsigned long i;
if (hole_end > KEXEC_CRASH_CONTROL_MEMORY_LIMIT)
break;
/* See if I overlap any of the segments */
for (i = 0; i < image->nr_segments; i++) { // pxl: max 16 loops, all existent segments are not overlapped, though may not sorted.
unsigned long mstart, mend;
mstart = image->segment[i].mem;
mend = mstart + image->segment[i].memsz - 1;
if ((hole_end >= mstart) && (hole_start <= mend)) {
/* Advance the hole to the end of the segment */
hole_start = (mend + (size - 1)) & ~(size - 1);
hole_end = hole_start + size - 1;
break; // pxl: If overlap was found, break for loop, @hole_end starts after the overlapped segment area, and will while loop again
}
}
/* If I don't overlap any segments I have found my hole! */
if (i == image->nr_segments) {
pages = pfn_to_page(hole_start >> PAGE_SHIFT);
image->control_page = hole_end;
break; // pxl: no overlap with all the segments, get the result and break the while loop. END.
}
}
So, the worst "while" loops in theory would be (image->nr_segments + 1), no?
Regards,
Xunlei
On 12/09/16 at 03:16pm, Xunlei Pang wrote:
> On 12/09/2016 at 01:13 PM, zhong jiang wrote:
> > On 2016/12/8 17:41, Xunlei Pang wrote:
> >> On 12/08/2016 at 10:37 AM, zhongjiang wrote:
> >>> From: zhong jiang <[email protected]>
> >>>
> >>> A soft lookup will occur when I run trinity in syscall kexec_load.
> >>> the corresponding stack information is as follows.
> >>>
> >>> [ 237.235937] BUG: soft lockup - CPU#6 stuck for 22s! [trinity-c6:13859]
> >>> [ 237.242699] Kernel panic - not syncing: softlockup: hung tasks
> >>> [ 237.248573] CPU: 6 PID: 13859 Comm: trinity-c6 Tainted: G O L ----V------- 3.10.0-327.28.3.35.zhongjiang.x86_64 #1
> >>> [ 237.259984] Hardware name: Huawei Technologies Co., Ltd. Tecal BH622 V2/BC01SRSA0, BIOS RMIBV386 06/30/2014
> >>> [ 237.269752] ffffffff8187626b 0000000018cfde31 ffff88184c803e18 ffffffff81638f16
> >>> [ 237.277471] ffff88184c803e98 ffffffff8163278f 0000000000000008 ffff88184c803ea8
> >>> [ 237.285190] ffff88184c803e48 0000000018cfde31 ffff88184c803e67 0000000000000000
> >>> [ 237.292909] Call Trace:
> >>> [ 237.295404] <IRQ> [<ffffffff81638f16>] dump_stack+0x19/0x1b
> >>> [ 237.301352] [<ffffffff8163278f>] panic+0xd8/0x214
> >>> [ 237.306196] [<ffffffff8111d6fc>] watchdog_timer_fn+0x1cc/0x1e0
> >>> [ 237.312157] [<ffffffff8111d530>] ? watchdog_enable+0xc0/0xc0
> >>> [ 237.317955] [<ffffffff810aa182>] __hrtimer_run_queues+0xd2/0x260
> >>> [ 237.324087] [<ffffffff810aa720>] hrtimer_interrupt+0xb0/0x1e0
> >>> [ 237.329963] [<ffffffff8164ae5c>] ? call_softirq+0x1c/0x30
> >>> [ 237.335500] [<ffffffff81049a77>] local_apic_timer_interrupt+0x37/0x60
> >>> [ 237.342228] [<ffffffff8164bacf>] smp_apic_timer_interrupt+0x3f/0x60
> >>> [ 237.348771] [<ffffffff8164a11d>] apic_timer_interrupt+0x6d/0x80
> >>> [ 237.354967] <EOI> [<ffffffff810f3a00>] ? kimage_alloc_control_pages+0x80/0x270
> >>> [ 237.362875] [<ffffffff811c3ebe>] ? kmem_cache_alloc_trace+0x1ce/0x1f0
> >>> [ 237.369592] [<ffffffff810f362f>] ? do_kimage_alloc_init+0x1f/0x90
> >>> [ 237.375992] [<ffffffff810f3d1a>] kimage_alloc_init+0x12a/0x180
> >>> [ 237.382103] [<ffffffff810f3f9a>] SyS_kexec_load+0x20a/0x260
> >>> [ 237.387957] [<ffffffff816494c9>] system_call_fastpath+0x16/0x1b
> >>>
> >>> the first time allocate control pages may take too much time because
> >>> crash_res.end can be set to a higher value. we need to add cond_resched
> >>> to avoid the issue.
> >>>
> >>> The patch have been tested and above issue is not appear.
> >>>
> >>> Signed-off-by: zhong jiang <[email protected]>
> >>> ---
> >>> kernel/kexec_core.c | 2 ++
> >>> 1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> >>> index 5616755..bfc9621 100644
> >>> --- a/kernel/kexec_core.c
> >>> +++ b/kernel/kexec_core.c
> >>> @@ -441,6 +441,8 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
> >>> while (hole_end <= crashk_res.end) {
> >>> unsigned long i;
> >>>
> >>> + cond_resched();
> >>> +
> >> I can't see why it would take a long time to loop inside, the job it does is simply to find a control area
> >> not overlapped with image->segment[], you can see the loop "for (i = 0; i < image->nr_segments; i++)",
> >> @hole_end will be advanced to the end of its next nearby segment once overlap was detected each loop,
> >> also there are limited (<=16) segments, so it won't take long to locate the right area.
> >>
> >> Am I missing something?
> >>
> >> Regards,
> >> Xunlei
> > if the crashkernel = auto is set in cmdline. it represent crashk_res.end will exceed to 4G, the first allocate control pages will
> > loop million times. if we set crashk_res.end to the higher value manually, you can image....
>
> How does "loop million times" happen? See my inlined comments prefixed with "pxl".
>
> kimage_alloc_crash_control_pages():
> while (hole_end <= crashk_res.end) {
> unsigned long i;
>
> if (hole_end > KEXEC_CRASH_CONTROL_MEMORY_LIMIT)
> break;
> /* See if I overlap any of the segments */
> for (i = 0; i < image->nr_segments; i++) { // pxl: max 16 loops, all existent segments are not overlapped, though may not sorted.
> unsigned long mstart, mend;
>
> mstart = image->segment[i].mem;
> mend = mstart + image->segment[i].memsz - 1;
> if ((hole_end >= mstart) && (hole_start <= mend)) {
> /* Advance the hole to the end of the segment */
> hole_start = (mend + (size - 1)) & ~(size - 1);
> hole_end = hole_start + size - 1;
> break; // pxl: If overlap was found, break for loop, @hole_end starts after the overlapped segment area, and will while loop again
> }
> }
> /* If I don't overlap any segments I have found my hole! */
> if (i == image->nr_segments) {
> pages = pfn_to_page(hole_start >> PAGE_SHIFT);
> image->control_page = hole_end;
> break; // pxl: no overlap with all the segments, get the result and break the while loop. END.
> }
> }
>
> So, the worst "while" loops in theory would be (image->nr_segments + 1), no?
It's very interesting. I got the different result by mental arithmatic.
Assume nr_segments is 16, and they are placed in continuous physical
memory, then in the first while loop, it will failed in image->segment[0]
and adjust hole_start and hole_end. Then it failed in 2nd while loop
after comparing with image->segment[0] and image->segment[1]. Finally it
will get a new position after image->segment[15] after 16 comparision in
the 16th while loop. So the amount should be (1+2+3+3+16) which is
(1+16)*8, 136 times.
Not sure if the counting is right, I am wondering how it will loop
millions of times even though crashk_res.end will exceed to 4G. The
times should not be related to how much memory resreved, only the
nr_segments, maybe I am wrong.
Thanks
Baoquan
On 12/19/2016 at 11:23 AM, Baoquan He wrote:
> On 12/09/16 at 03:16pm, Xunlei Pang wrote:
>> On 12/09/2016 at 01:13 PM, zhong jiang wrote:
>>> On 2016/12/8 17:41, Xunlei Pang wrote:
>>>> On 12/08/2016 at 10:37 AM, zhongjiang wrote:
>>>>> From: zhong jiang <[email protected]>
>>>>>
>>>>> A soft lookup will occur when I run trinity in syscall kexec_load.
>>>>> the corresponding stack information is as follows.
>>>>>
>>>>> [ 237.235937] BUG: soft lockup - CPU#6 stuck for 22s! [trinity-c6:13859]
>>>>> [ 237.242699] Kernel panic - not syncing: softlockup: hung tasks
>>>>> [ 237.248573] CPU: 6 PID: 13859 Comm: trinity-c6 Tainted: G O L ----V------- 3.10.0-327.28.3.35.zhongjiang.x86_64 #1
>>>>> [ 237.259984] Hardware name: Huawei Technologies Co., Ltd. Tecal BH622 V2/BC01SRSA0, BIOS RMIBV386 06/30/2014
>>>>> [ 237.269752] ffffffff8187626b 0000000018cfde31 ffff88184c803e18 ffffffff81638f16
>>>>> [ 237.277471] ffff88184c803e98 ffffffff8163278f 0000000000000008 ffff88184c803ea8
>>>>> [ 237.285190] ffff88184c803e48 0000000018cfde31 ffff88184c803e67 0000000000000000
>>>>> [ 237.292909] Call Trace:
>>>>> [ 237.295404] <IRQ> [<ffffffff81638f16>] dump_stack+0x19/0x1b
>>>>> [ 237.301352] [<ffffffff8163278f>] panic+0xd8/0x214
>>>>> [ 237.306196] [<ffffffff8111d6fc>] watchdog_timer_fn+0x1cc/0x1e0
>>>>> [ 237.312157] [<ffffffff8111d530>] ? watchdog_enable+0xc0/0xc0
>>>>> [ 237.317955] [<ffffffff810aa182>] __hrtimer_run_queues+0xd2/0x260
>>>>> [ 237.324087] [<ffffffff810aa720>] hrtimer_interrupt+0xb0/0x1e0
>>>>> [ 237.329963] [<ffffffff8164ae5c>] ? call_softirq+0x1c/0x30
>>>>> [ 237.335500] [<ffffffff81049a77>] local_apic_timer_interrupt+0x37/0x60
>>>>> [ 237.342228] [<ffffffff8164bacf>] smp_apic_timer_interrupt+0x3f/0x60
>>>>> [ 237.348771] [<ffffffff8164a11d>] apic_timer_interrupt+0x6d/0x80
>>>>> [ 237.354967] <EOI> [<ffffffff810f3a00>] ? kimage_alloc_control_pages+0x80/0x270
>>>>> [ 237.362875] [<ffffffff811c3ebe>] ? kmem_cache_alloc_trace+0x1ce/0x1f0
>>>>> [ 237.369592] [<ffffffff810f362f>] ? do_kimage_alloc_init+0x1f/0x90
>>>>> [ 237.375992] [<ffffffff810f3d1a>] kimage_alloc_init+0x12a/0x180
>>>>> [ 237.382103] [<ffffffff810f3f9a>] SyS_kexec_load+0x20a/0x260
>>>>> [ 237.387957] [<ffffffff816494c9>] system_call_fastpath+0x16/0x1b
>>>>>
>>>>> the first time allocate control pages may take too much time because
>>>>> crash_res.end can be set to a higher value. we need to add cond_resched
>>>>> to avoid the issue.
>>>>>
>>>>> The patch have been tested and above issue is not appear.
>>>>>
>>>>> Signed-off-by: zhong jiang <[email protected]>
>>>>> ---
>>>>> kernel/kexec_core.c | 2 ++
>>>>> 1 file changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>>>>> index 5616755..bfc9621 100644
>>>>> --- a/kernel/kexec_core.c
>>>>> +++ b/kernel/kexec_core.c
>>>>> @@ -441,6 +441,8 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
>>>>> while (hole_end <= crashk_res.end) {
>>>>> unsigned long i;
>>>>>
>>>>> + cond_resched();
>>>>> +
>>>> I can't see why it would take a long time to loop inside, the job it does is simply to find a control area
>>>> not overlapped with image->segment[], you can see the loop "for (i = 0; i < image->nr_segments; i++)",
>>>> @hole_end will be advanced to the end of its next nearby segment once overlap was detected each loop,
>>>> also there are limited (<=16) segments, so it won't take long to locate the right area.
>>>>
>>>> Am I missing something?
>>>>
>>>> Regards,
>>>> Xunlei
>>> if the crashkernel = auto is set in cmdline. it represent crashk_res.end will exceed to 4G, the first allocate control pages will
>>> loop million times. if we set crashk_res.end to the higher value manually, you can image....
>> How does "loop million times" happen? See my inlined comments prefixed with "pxl".
>>
>> kimage_alloc_crash_control_pages():
>> while (hole_end <= crashk_res.end) {
>> unsigned long i;
>>
>> if (hole_end > KEXEC_CRASH_CONTROL_MEMORY_LIMIT)
>> break;
>> /* See if I overlap any of the segments */
>> for (i = 0; i < image->nr_segments; i++) { // pxl: max 16 loops, all existent segments are not overlapped, though may not sorted.
>> unsigned long mstart, mend;
>>
>> mstart = image->segment[i].mem;
>> mend = mstart + image->segment[i].memsz - 1;
>> if ((hole_end >= mstart) && (hole_start <= mend)) {
>> /* Advance the hole to the end of the segment */
>> hole_start = (mend + (size - 1)) & ~(size - 1);
>> hole_end = hole_start + size - 1;
>> break; // pxl: If overlap was found, break for loop, @hole_end starts after the overlapped segment area, and will while loop again
>> }
>> }
>> /* If I don't overlap any segments I have found my hole! */
>> if (i == image->nr_segments) {
>> pages = pfn_to_page(hole_start >> PAGE_SHIFT);
>> image->control_page = hole_end;
>> break; // pxl: no overlap with all the segments, get the result and break the while loop. END.
>> }
>> }
>>
>> So, the worst "while" loops in theory would be (image->nr_segments + 1), no?
> It's very interesting. I got the different result by mental arithmatic.
Hi Baoquan,
I meant the "while" loops excluding the "for" loops considering it's always limited to 16 each while loop.
So basically we have the same view :-)
Regards,
Xunlei
> Assume nr_segments is 16, and they are placed in continuous physical
> memory, then in the first while loop, it will failed in image->segment[0]
> and adjust hole_start and hole_end. Then it failed in 2nd while loop
> after comparing with image->segment[0] and image->segment[1]. Finally it
> will get a new position after image->segment[15] after 16 comparision in
> the 16th while loop. So the amount should be (1+2+3+3+16) which is
> (1+16)*8, 136 times.
>
> Not sure if the counting is right, I am wondering how it will loop
> millions of times even though crashk_res.end will exceed to 4G. The
> times should not be related to how much memory resreved, only the
> nr_segments, maybe I am wrong.
>
> Thanks
> Baoquan
>
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