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The following warning triggers with a new unit test that stresses the
device-dax interface.
===============================
[ ERR: suspicious RCU usage. ]
4.11.0-rc4+ #1049 Tainted: G O
-------------------------------
./include/linux/rcupdate.h:521 Illegal context switch in RCU read-side critical section!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 0
2 locks held by fio/9070:
#0: (&mm->mmap_sem){++++++}, at: [<ffffffff8d0739d7>] __do_page_fault+0x167/0x4f0
#1: (rcu_read_lock){......}, at: [<ffffffffc03fbd02>] dax_dev_huge_fault+0x32/0x620 [dax]
Call Trace:
dump_stack+0x86/0xc3
lockdep_rcu_suspicious+0xd7/0x110
___might_sleep+0xac/0x250
__might_sleep+0x4a/0x80
__alloc_pages_nodemask+0x23a/0x360
alloc_pages_current+0xa1/0x1f0
pte_alloc_one+0x17/0x80
__pte_alloc+0x1e/0x120
__get_locked_pte+0x1bf/0x1d0
insert_pfn.isra.70+0x3a/0x100
? lookup_memtype+0xa6/0xd0
vm_insert_mixed+0x64/0x90
dax_dev_huge_fault+0x520/0x620 [dax]
? dax_dev_huge_fault+0x32/0x620 [dax]
dax_dev_fault+0x10/0x20 [dax]
__do_fault+0x1e/0x140
__handle_mm_fault+0x9af/0x10d0
handle_mm_fault+0x16d/0x370
? handle_mm_fault+0x47/0x370
__do_page_fault+0x28c/0x4f0
trace_do_page_fault+0x58/0x2a0
do_async_page_fault+0x1a/0xa0
async_page_fault+0x28/0x30
Inserting a page table entry may trigger an allocation while we are
holding a read lock to keep the device instance alive for the duration
of the fault. Use srcu for this keep-alive protection.
Fixes: dee4107924 ("/dev/dax, core: file operations and dax-mmap")
Cc: <stable@vger.kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
33 lines
950 B
Plaintext
33 lines
950 B
Plaintext
menuconfig DEV_DAX
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tristate "DAX: direct access to differentiated memory"
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default m if NVDIMM_DAX
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depends on TRANSPARENT_HUGEPAGE
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select SRCU
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help
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Support raw access to differentiated (persistence, bandwidth,
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latency...) memory via an mmap(2) capable character
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device. Platform firmware or a device driver may identify a
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platform memory resource that is differentiated from the
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baseline memory pool. Mappings of a /dev/daxX.Y device impose
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restrictions that make the mapping behavior deterministic.
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if DEV_DAX
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config DEV_DAX_PMEM
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tristate "PMEM DAX: direct access to persistent memory"
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depends on LIBNVDIMM && NVDIMM_DAX
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default DEV_DAX
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help
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Support raw access to persistent memory. Note that this
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driver consumes memory ranges allocated and exported by the
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libnvdimm sub-system.
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Say Y if unsure
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config NR_DEV_DAX
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int "Maximum number of Device-DAX instances"
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default 32768
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range 256 2147483647
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endif
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