Messages in this thread | | | From | Jianyong Wu <> | Subject | RE: [PATCH v3] arm64/mm: avoid fixmap race condition when create pud mapping | Date | Thu, 6 Jan 2022 10:13:06 +0000 |
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Hi Catalin,
I test this patch in your way using both EDK2 V2.6 and EDK2 v2.7. it's peculiar that this issue shows up on v2.6 but not on v2.7. For now, I only find that if "CONFIG_DEBUG_LOCK_ALLOC" is enabled, the kernel boot will hang. However, I can't debug it by printk as this issue happens before pl11 is ready. I will go on debugging, but very appreciated if someone can give some hints on it.
Thanks Jianyong
> -----Original Message----- > From: Catalin Marinas <catalin.marinas@arm.com> > Sent: Thursday, January 6, 2022 2:04 AM > To: Jianyong Wu <Jianyong.Wu@arm.com> > Cc: will@kernel.org; Anshuman Khandual <Anshuman.Khandual@arm.com>; > akpm@linux-foundation.org; david@redhat.com; quic_qiancai@quicinc.com; > ardb@kernel.org; linux-kernel@vger.kernel.org; linux-arm- > kernel@lists.infradead.org; gshan@redhat.com; Justin He > <Justin.He@arm.com>; nd <nd@arm.com> > Subject: Re: [PATCH v3] arm64/mm: avoid fixmap race condition when create > pud mapping > > On Thu, Dec 16, 2021 at 04:28:12PM +0800, Jianyong Wu wrote: > > The 'fixmap' is a global resource and is used recursively by create > > pud mapping(), leading to a potential race condition in the presence > > of a concurrent call to alloc_init_pud(): > > > > kernel_init thread virtio-mem workqueue thread > > ================== =========================== > > > > alloc_init_pud(...) alloc_init_pud(...) > > pudp = pud_set_fixmap_offset(...) pudp = pud_set_fixmap_offset(...) > > READ_ONCE(*pudp) > > pud_clear_fixmap(...) > > READ_ONCE(*pudp) // CRASH! > > > > As kernel may sleep during creating pud mapping, introduce a mutex > > lock to serialise use of the fixmap entries by alloc_init_pud(). > > > > Signed-off-by: Jianyong Wu <jianyong.wu@arm.com> > > I tried to queue this patch but with certain configurations it doesn't boot > under Qemu. Starting from defconfig, update .config with (I had this in one > of my build scripts): > > $ ./scripts/config \ > -e DEBUG_KERNEL \ > -e DEBUG_PAGEALLOC \ > -e DEBUG_PAGEALLOC_ENABLE_DEFAULT \ > -e DEBUG_WX \ > -e DEBUG_SET_MODULE_RONX \ > -e DEBUG_ALIGN_RODATA \ > -e ARM64_PTDUMP_DEBUGFS \ > -e DEBUG_OBJECTS \ > -e DEBUG_OBJECTS_FREE \ > -e DEBUG_OBJECTS_TIMERS \ > -e DEBUG_KOBJECT_RELEASE \ > -e DEBUG_LOCKING_API_SELFTESTS \ > -e DEBUG_PREEMPT \ > -e DEBUG_TIMEKEEPING \ > -e DEBUG_VM \ > -e DEBUG_VM_VMACACHE \ > -e DEBUG_VM_RB \ > -e DEBUG_VM_PGFLAGS \ > -e DEBUG_VIRTUAL \ > -e DEBUG_LIST \ > -e DEBUG_PI_LIST \ > -e DEBUG_SG \ > -e PROVE_LOCKING \ > -e DEBUG_RT_MUTEXES \ > -e DEBUG_ATOMIC_SLEEP \ > -e ATOMIC64_SELFTEST > > It stop after exiting the EFI boot services. I did not have time to debug. > > -- > Catalin
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