New submission from Paul Swirhun <paulswir...@gmail.com>:
mmap (example, as used in python-periphery) duplicates writes, compared to
devmem and a c-periphery on an ARM64 platform (Zynq/Petalinux/Yocto). There are
various other reports of duplicated writes using mmap suggesting it is a bug.
Example:
fd = os.open("/dev/mem", os.O_RDWR | os.O_SYNC)
mapping = mmap.mmap(fd, 4096, flags=mmap.MAP_SHARED, prot=(mmap.PROT_READ |
mmap.PROT_WRITE), offset=0x80000000)
mapping.write(bytearray([0x0,]* 4)) # results in 2 writes, should be 1
mapping.write(bytearray([0x0,]* 8)) # results in 4 writes, should be 1-2
depending on bus width (32b vs 64b)
# OR:
mapping[0:4] = struct.pack("=L", 0x0) # results in 2 writes, should be 1
----------
components: Library (Lib)
messages: 386501
nosy: psswirhun
priority: normal
severity: normal
status: open
title: MMAP duplicate reads and writes on ARM64 platform
versions: Python 3.7
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue43131>
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