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runtime: drop NetBSD kernel bug sysmon workaround fixed in NetBSD 9.2 #46495

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prattmic opened this issue Jun 1, 2021 · 6 comments
Open

runtime: drop NetBSD kernel bug sysmon workaround fixed in NetBSD 9.2 #46495

prattmic opened this issue Jun 1, 2021 · 6 comments
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsFix The path to resolution is known, but the work has not been done. OS-NetBSD
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@prattmic
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prattmic commented Jun 1, 2021 •
edited

#42515 identified a NetBSD kernel bug (kern/50094) affecting the Go runtime. http://golang.org/cl/277332 introduced a (rather subpar) workaround for this issue.

@jdolecek-zz notes that the fix for this bug is included in NetBSD 9.2, making the workaround unnecessary.

Ideally we just drop http://golang.org/cl/277332, but this depends on our support policy for NetBSD. https://github.com/golang/go/wiki/NetBSD states that we currently support NetBSD 7+, but not what the official policy is. (OTOH, e.g., OpenBSD is explicitly supported only for the two most recent releases: https://github.com/golang/go/wiki/OpenBSD#longterm-support).

Based on my reading of https://www.netbsd.org/releases/formal.html, my interpretation would be that Go should support NetBSD 8 and 9 (and presumably drop 8 when 10 is released?). Do others agree? If so, we should probably add a version check to the workaround and keep it until NetBSD 9 is dropped.

cc @bsiegert @dmitshur @mknyszek
@dmitshur
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dmitshur commented Jun 1, 2021

I agree we should find a support policy that automatically drops support for old NetBSD releases when new ones are made, similar to how OpenBSD has one.

CC @golang/release.

@tklauser
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tklauser commented Jun 3, 2021

Another option to already disable the workaround for NetBSD 9.2 while still retaining compatibility with older NetBSD versions would be to check sysctlInt([]uint32{_CTL_KERN, _KERN_OSREV}) in runtime.osinit and disable the fix if that value is >= 902000000.

I've sent https://golang.org/cl/324472 implementing that.

@gopherbot
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Change https://golang.org/cl/324472 mentions this issue: runtime: skip sysmon workaround on NetBSD >= 9.2

@cherrymui cherrymui added the NeedsFix The path to resolution is known, but the work has not been done. label Jun 7, 2021
@cherrymui cherrymui added this to the Backlog milestone Jun 7, 2021
gopherbot pushed a commit that referenced this issue Aug 16, 2021
@tklauser
runtime: skip sysmon workaround on NetBSD >= 9.2
6406227 
Detect the NetBSD version in osinit and only enable the workaround for
the kernel bug identified in #42515 for NetBSD versions older than 9.2.

For #42515
For #46495

Change-Id: I808846c7f8e47e5f7cc0a2f869246f4bd90d8e22
Reviewed-on: https://go-review.googlesource.com/c/go/+/324472
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Trust: Benny Siegert <bsiegert@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
@hzzb
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hzzb commented Mar 9, 2022

Another option to already disable the workaround for NetBSD 9.2 while still retaining compatibility with older NetBSD versions would be to check sysctlInt([]uint32{_CTL_KERN, _KERN_OSREV}) in runtime.osinit and disable the fix if that value is >= 902000000.

I've sent https://golang.org/cl/324472 implementing that.

The CL you sent does os version checking in os_netbsd.go. It seems to me that no GOOS == "netbsd" rechecking needed in sysmon. Because needSysmonWorkaround would be true only on netbsd platform. right?

CC @tklauser

@tklauser
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Another option to already disable the workaround for NetBSD 9.2 while still retaining compatibility with older NetBSD versions would be to check sysctlInt([]uint32{_CTL_KERN, _KERN_OSREV}) in runtime.osinit and disable the fix if that value is >= 902000000.
I've sent https://golang.org/cl/324472 implementing that.

The CL you sent does os version checking in os_netbsd.go. It seems to me that no GOOS == "netbsd" rechecking needed in sysmon. Because needSysmonWorkaround would be true only on netbsd platform. right?

CC @tklauser

Yes, needSysmonWorkaround will only be true on netbsd. However, the additional GOOS == "netbsd" check will lead the compiler to omit the entire branch on non-netbsd platforms, i.e. needSysmonWorkaround will not need to be checked at runtime.

@hzzb
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hzzb commented Mar 10, 2022

Another option to already disable the workaround for NetBSD 9.2 while still retaining compatibility with older NetBSD versions would be to check sysctlInt([]uint32{_CTL_KERN, _KERN_OSREV}) in runtime.osinit and disable the fix if that value is >= 902000000.
I've sent https://golang.org/cl/324472 implementing that.

The CL you sent does os version checking in os_netbsd.go. It seems to me that no GOOS == "netbsd" rechecking needed in sysmon. Because needSysmonWorkaround would be true only on netbsd platform. right?
CC @tklauser

Yes, needSysmonWorkaround will only be true on netbsd. However, the additional GOOS == "netbsd" check will lead the compiler to omit the entire branch on non-netbsd platforms, i.e. needSysmonWorkaround will not need to be checked at runtime.

Got it. Thanks for your explanation.

@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Jul 7, 2022
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsFix The path to resolution is known, but the work has not been done. OS-NetBSD
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@tklauser @prattmic @dmitshur @gopherbot @cherrymui @hzzb