Package: rtl-sdr Version: 0.6.0-4 Severity: normal X-Debbugs-Cc: offri...@gmail.com
Dear Maintainer, On ARM/ARM64 systems, according to (1), the Linux kernel has a bug that causes the zerocopy system using mmap to fail. Rtl-sdr contains a workaround that determines whether this bug exists by verifying whether the mapping returned by mmap is zeroed out. Recently, this workaround fails to identify the bug on my hardware most of the times, leading to the rtl tools to fail. The result is that rtl_tcp outputs only zeros without any error. rtl_test does output lost bytes. My assumption is that the memory map returned accidentally is zero while trying to detect the bug. I'm running this on an Odroid N2+. The rtl tools report whether the bug is detected, by outputting: Detected Kernel usbfs mmap() bug, falling back to buffers in userspace If the rtl tools report this detection, they will consequently work fine, but most of the times this message is not reported and the tools fail. rtl-sdr has a cmake option to disable zerocopy. After compiling the tool myself with zerocopy off, they consistently work. Maybe it is therefore a good idea to disable this option on ARM/ARM64 platforms? I also can't really find what happend with this kernel bug. The bug is already reported in 2018 here: (2), and reading the threads it looks like there is a solution, as far as I can understand. I'm not sure where to raise this -- what would be a good place to raise this? Finally, I can't find where I can report this upstream. There are several repositories for rtl-sdr, but the seemingly most active one on (3) does not allow me to register an account to report it. (1) https://sources.debian.org/patches/rtl-sdr/0.6-1/0002-lib-Add-workaround- for-Linux-usbfs-mmap-bug.patch/ (2) https://www.spinics.net/lists/arm-kernel/msg685598.html (3) https://gitea.osmocom.org/sdr/rtl-sdr Regards, André -- System Information: Debian Release: bookworm/sid APT prefers jammy-updates APT policy: (500, 'jammy-updates'), (500, 'jammy-security'), (500, 'jammy'), (100, 'jammy-backports') Architecture: arm64 (aarch64) Kernel: Linux 4.9.337-132 (SMP w/6 CPU threads; PREEMPT) Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set Shell: /bin/sh linked to /usr/bin/dash Init: systemd (via /run/systemd/system) LSM: AppArmor: enabled Versions of packages rtl-sdr depends on: ii libc6 2.35-0ubuntu3.1 ii librtlsdr0 0.6.0-4 rtl-sdr recommends no packages. rtl-sdr suggests no packages. -- no debconf information
