Re: [PATCH] xen/sched: set all sched_resource data inside locked region for new cpu

[Jan Beulich <jbeulich@xxxxxxxx>]

On 15.05.2024 17:27, Andrew Cooper wrote:
> On 15/05/2024 4:25 pm, Juergen Gross wrote:
>> When adding a cpu to a scheduler, set all data items of struct
>> sched_resource inside the locked region, as otherwise a race might
>> happen (e.g. when trying to access the cpupool of the cpu):
>>
>> (XEN) ----[ Xen-4.19.0-1-d  x86_64  debug=y  Tainted:     H  ]----
>> (XEN) CPU:    45
>> (XEN) RIP:    e008:[<ffff82d040244cbf>]
>> common/sched/credit.c#csched_load_balance+0x41/0x877
>> (XEN) RFLAGS: 0000000000010092   CONTEXT: hypervisor
>> (XEN) rax: ffff82d040981618   rbx: ffff82d040981618   rcx:
>> 0000000000000000
>> (XEN) rdx: 0000003ff68cd000   rsi: 000000000000002d   rdi:
>> ffff83103723d450
>> (XEN) rbp: ffff83207caa7d48   rsp: ffff83207caa7b98   r8:
>> 0000000000000000
>> (XEN) r9:  ffff831037253cf0   r10: ffff83103767c3f0   r11:
>> 0000000000000009
>> (XEN) r12: ffff831037237990   r13: ffff831037237990   r14:
>> ffff831037253720
>> (XEN) r15: 0000000000000000   cr0: 000000008005003b   cr4:
>> 0000000000f526e0
>> (XEN) cr3: 000000005bc2f000   cr2: 0000000000000010
>> (XEN) fsb: 0000000000000000   gsb: 0000000000000000   gss:
>> 0000000000000000
>> (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: 0000   cs: e008
>> (XEN) Xen code around <ffff82d040244cbf>
>> (common/sched/credit.c#csched_load_balance+0x41/0x877):
>> (XEN)  48 8b 0c 10 48 8b 49 08 <48> 8b 79 10 48 89 bd b8 fe ff ff 49
>> 8b 4e 28 48
>> <snip>
>> (XEN) Xen call trace:
>> (XEN)    [<ffff82d040244cbf>] R
>> common/sched/credit.c#csched_load_balance+0x41/0x877
>> (XEN)    [<ffff82d040245a18>] F
>> common/sched/credit.c#csched_schedule+0x36a/0x69f
>> (XEN)    [<ffff82d040252644>] F common/sched/core.c#do_schedule+0xe8/0x433
>> (XEN)    [<ffff82d0402572dd>] F common/sched/core.c#schedule+0x2e5/0x2f9
>> (XEN)    [<ffff82d040232f35>] F common/softirq.c#__do_softirq+0x94/0xbe
>> (XEN)    [<ffff82d040232fc8>] F do_softirq+0x13/0x15
>> (XEN)    [<ffff82d0403075ef>] F arch/x86/domain.c#idle_loop+0x92/0xe6
>>
>> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> Fixes: a8c6c623192e ("sched: clarify use cases of schedule_cpu_switch()")
>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> 
> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Tested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> 
> Thankyou for the quick turnaround.  I'll fix the wrapping of the commit
> message on commit.  Not sure what went wrong on my original outgoing email.

Didn't you rush this in a little too fast? No matter how obvious it might seem,
there was no sched/ maintainer ack so far ...

Jan