On Fedora 32 Beta with its 5.6 kernel, the system freezes regularly due to unpatched bugs in the default BFQ scheduler. For me, the impact is severe: running basic "dnf install" or "dnf remove" commands results in a total system freeze about 10% of the time. This issue, and particularly its impact on dnf, was previously noted on the kernel.org tracker by another user (Patrick Dung): https://bugzilla.kernel.org/show_bug.cgi?id=205447#c70 I posted my experience, including how I'm able to reproduce it consistently, beginning in Comment 72. As Comment 77 notes, fixes for BFQ were merged into 5.7.0, but they haven't (yet) been backported to 5.6. Please merge those fixes into the Fedora 32 5.6 kernel. Given the severity of the problem (frequent freezes when running dnf), I believe this ought to be considered a blocking bug for the Fedora 32 final release. Version-Release number of selected component (if applicable): 5.6.5-300 (and earlier, including 5.6.2) How reproducible: For me, 100% Steps to Reproduce: 1. Create a new VMware VM with 1 CPU assigned. (NOTE: The freeze isn't consistently reproducible with >1 CPU.) 2. Install Fedora 32 Beta using the netinstall Server ISO. Choose "Minimum" software selection (may not be necessary). 3. Run this script, which installs and removes packages in a loop: ======================================== #!/bin/bash set -e while true; do dnf --setopt=keepcache=True -y install nano sleep 2 dnf -y remove nano sleep 2 done ======================================== Actual results: The VM consistently freezes in under a minute of running the script. If I switch to the mq-deadline scheduler -OR- boot with kernel 5.7.0-rc1 (from Fedora 33 repo), the freeze no longer occurs.
I posted a call trace of the crash here: https://bugzilla.kernel.org/show_bug.cgi?id=205447#c87 Paolo Valente confirms that it should be fixed by the 5.7 patches (and again, I can't reproduce it on 5.7.0-rc1). I should also point out that this issue with dnf freezing appears to be NEW in Fedora 32 -- or at least something has made it much worse. On Fedora 31 with 5.5.17-200, my script never freezes (after 30 minutes of execution).
The BFQ fixes should be in 5.6.7, released yesterday. Will re-test when kernel-5.6.7 packages reach updates-testing.
kernel-5.6.7-300 fixes it for me. No freeze running the same script for 30 minutes.
I have one F32 machine that experienced the freeze repeatedly on the 5.6.6 kernel. After running the 5.6.7 and later kernels, it has never happened.
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