Date: Mon, 10 Aug 2020 11:59:59 +0100 From: Alexandre Levy <a13xlevy@gmail.com> To: Hans Petter Selasky <hps@selasky.org> Cc: freebsd-current@freebsd.org Subject: Re: Kernel crash during video transcoding Message-ID: <CAEWSB33_ka2aQb81UmODu72Be_9Vvqi4Qb-jfXHEZ1HgCqwADQ@mail.gmail.com> In-Reply-To: <CAEWSB30YNwQ7Bpv00P-B=TTHCqT_aFm30552n51Pic1uN5hnZQ@mail.gmail.com> References: <CAEWSB323c2zapSG30OS5T30Wd_bpT=7NbvrPtsyQDRRHQUf7qA@mail.gmail.com> <13793020-1bde-b13f-65e3-909e27d876ad@selasky.org> <CAEWSB323KtVrixgRyKsekdgcGjFm4kUqG6qDE59Aev3Cc6sYBg@mail.gmail.com> <4e9d9a89-4883-1f1c-c796-e5925fd171cc@selasky.org> <CAEWSB30YNwQ7Bpv00P-B=TTHCqT_aFm30552n51Pic1uN5hnZQ@mail.gmail.com>
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I could reproduce with GENERIC kernel and i915 kms compiled with DEBUG and
I got this additional info (still no crash dump though) :
Kernel page fault with the following non-sleepable locks held:
kernel: exclusive rw vm object (vm object) r =3D 0 (0xfffff8037533bc60)
locked @
/usr/ports/graphics/drm-devel-kmod/work/drm-kmod-drm_v5.3_4/drivers/gpu/drm=
/i915/intel_freebsd.c:186
Looking at the code, the error happens during the call to VM_OBJECT_WLOCK
(memory page locking for write ?) in the intel_freebsd.c (see [1] below).
I'm out for a few days but I'll try to dig more into it when I'm back next
weekend although I have no experience in the drm-devel-kmod codebase. In
the meantime if you have any suggestions on debugging this further I'm
happy to follow them.
Thanks again.
[1] i915/intel_freebsd.c
int
remap_io_mapping(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn, unsigned long size, struct io_mapping *iomap)
{
vm_page_t m;
vm_object_t vm_obj;
vm_memattr_t attr;
vm_paddr_t pa;
vm_pindex_t pidx, pidx_start;
int count, rc;
attr =3D iomap->attr;
count =3D size >> PAGE_SHIFT;
pa =3D pfn << PAGE_SHIFT;
pidx_start =3D OFF_TO_IDX(addr);
rc =3D 0;
vm_obj =3D vma->vm_obj;
vma->vm_pfn_first =3D pidx_start;
>>> VM_OBJECT_WLOCK(vm_obj); <<<
for (pidx =3D pidx_start; pidx < pidx_start + count;
pidx++, pa +=3D PAGE_SIZE) {
retry:
m =3D vm_page_grab(vm_obj, pidx, VM_ALLOC_NOCREAT);
if (m =3D=3D NULL) {
m =3D PHYS_TO_VM_PAGE(pa);
if (!vm_page_busy_acquire(m, VM_ALLOC_WAITFAIL))
goto retry;
if (vm_page_insert(m, vm_obj, pidx)) {
vm_page_xunbusy(m);
VM_OBJECT_WUNLOCK(vm_obj);
vm_wait(NULL);
VM_OBJECT_WLOCK(vm_obj);
goto retry;
}
vm_page_valid(m);
}
pmap_page_set_memattr(m, attr);
vma->vm_pfn_count++;
}
VM_OBJECT_WUNLOCK(vm_obj);
return (rc);
}
Le lun. 10 ao=C3=BBt 2020 =C3=A0 09:44, Alexandre Levy <a13xlevy@gmail.com>=
a =C3=A9crit :
> Ah thanks, I was doing a make config-recursive and that didn't show the
> DEBUG option. It's recompiling the module with DEBUG now.
>
> Le lun. 10 ao=C3=BBt 2020 =C3=A0 09:43, Hans Petter Selasky <hps@selasky.=
org> a
> =C3=A9crit :
>
>> On 2020-08-10 10:41, Alexandre Levy wrote:
>> > I'm recompiling the kernel using GENERIC at the moment but I'm not sur=
e
>> how
>> > to enable debugging in i915 kms, there is no compile option for that,
>> am I
>> > missing something ?
>>
>> Type:
>>
>> make config
>>
>> Before building the i915kms port, then there should be a DEBUG option
>> you can select.
>>
>> --HPS
>>
>
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