linux: workaround to avoid deadlock inside dl_iterate_phdr in glibc #57035
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vtjnash
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profiler
backport 1.11
Extend the fix for #43578 on Darwin to also cover the same bug in Glibc (and just assume other libc have the same bug). We cannot use the same atfork trick, since the atfork implementation of this in Glibc makes this unsafe to use this after fork, just like Darwin (though for different basic concurrency mistakes in each of their respective codes). Fix #57017
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Sounds like this introduced a deadlock elsewhere: #57058. FreeBSD tests timed out also on this branch: https://buildkite.com/julialang/julia-master/builds/43702#019461a2-569c-45b2-b720-8acf560eb139 |
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Removing the backport label as this shouldn't be backported as-is given that it introduces a regression |
ararslan
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Jan 18, 2025
This is Jameson's proposed amendment to the changes made in #57035 that introduced a deadlock on FreeBSD, amusingly in service of fixing a deadlock on Linux. On Linux and (non-macOS) BSD, instead of acquiring and releasing a lock on the profiler in `jl_with_stackwalk_lock`, we're just blocking the thread from receiving the profiler's `SIGUSR2` signal at all. This should fix #57058; I don't get the deadlock locally on FreeBSD with this change, but it's AArch64 instead of x86-64 like on CI, so let's see if this also makes CI happy. If so, closes #57059. Co-authored-by: Jameson Nash <vtjnash@gmail.com>
Closed
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Re-added the backport label, should only be backported in conjunction with #57089. |
vtjnash
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Feb 3, 2025
Restores #57035, undo #57089 for non-FreeBSD. While I suggested doing this change for all platforms, I forgot that means non-FreeBSD platforms become vulnerable again to the very deadlock problems that #57035 was required to prevent. That fix seems to not be viable on FreeBSD due to known libc implementation problems on that platform. However, upon closer inspection of the questionable design implementation decisions they seem to have made here, the platform is likely not currently vulnerable to this libunwind bug in the first place: https://github.com/lattera/freebsd/blob/master/libexec/rtld-elf/rtld_lock.c#L120
vtjnash
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Feb 3, 2025
Restores #57035, undo #57089 for non-FreeBSD. While I suggested doing this change for all platforms, I forgot that means non-FreeBSD platforms become vulnerable again to the very deadlock problems that #57035 was required to prevent. That fix seems to not be viable on FreeBSD due to known libc implementation problems on that platform. However, upon closer inspection of the questionable design implementation decisions they seem to have made here, the platform is likely not currently vulnerable to this libunwind bug in the first place: https://github.com/lattera/freebsd/blob/master/libexec/rtld-elf/rtld_lock.c#L120
vtjnash
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Feb 4, 2025
Restores #57035, undo #57089 for non-FreeBSD. While I suggested doing this change for all platforms, I forgot that means non-FreeBSD platforms become vulnerable again to the very deadlock problems that #57035 was required to prevent. That fix seems to not be viable on FreeBSD due to known libc implementation problems on that platform. However, upon closer inspection of the questionable design implementation decisions they seem to have made here, the platform is likely not currently vulnerable to this libunwind bug in the first place: https://github.com/lattera/freebsd/blob/master/libexec/rtld-elf/rtld_lock.c#L120
KristofferC
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Feb 6, 2025
Restores #57035, undo #57089 for non-FreeBSD. While I suggested doing this change for all platforms, I forgot that means non-FreeBSD platforms become vulnerable again to the very deadlock problems that #57035 was required to prevent. That fix seems to not be viable on FreeBSD due to known libc implementation problems on that platform. However, upon closer inspection of the questionable design implementation decisions they seem to have made here, the platform is likely not currently vulnerable to this libunwind bug in the first place: https://github.com/lattera/freebsd/blob/master/libexec/rtld-elf/rtld_lock.c#L120 (cherry picked from commit 2f0a523)
KristofferC
pushed a commit
that referenced
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Feb 6, 2025
Restores #57035, undo #57089 for non-FreeBSD. While I suggested doing this change for all platforms, I forgot that means non-FreeBSD platforms become vulnerable again to the very deadlock problems that #57035 was required to prevent. That fix seems to not be viable on FreeBSD due to known libc implementation problems on that platform. However, upon closer inspection of the questionable design implementation decisions they seem to have made here, the platform is likely not currently vulnerable to this libunwind bug in the first place: https://github.com/lattera/freebsd/blob/master/libexec/rtld-elf/rtld_lock.c#L120 (cherry picked from commit 2f0a523)
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Extend the fix for #43578 on Darwin to also cover the same bug in Glibc (and just assume other libc have the same bug). We cannot use the same atfork trick, since the atfork implementation of this in Glibc makes this unsafe to use this after fork, just like Darwin (though for different basic concurrency mistakes in each of their respective codes).
Fix #57017