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Core Dump When Using OpenMP on AWS Lambda #53955

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stuartmcmahon-h3d opened this issue Feb 20, 2022 · 4 comments
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Core Dump When Using OpenMP on AWS Lambda #53955

stuartmcmahon-h3d opened this issue Feb 20, 2022 · 4 comments
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@shiltian
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crash Prefer [crash-on-valid] or [crash-on-invalid] openmp

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@stuartmcmahon-h3d
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Since AWS Lambda does not support /dev/shm the OpenMP runtime causes a core dump. Output below:

OMP: Error #179: Function Can't open SHM2 failed:
OMP: System error #2: No such file or directory

To fix the issue we have to switch to an OpenMP runtime earlier than this commit:
changing OMP rtl to use shared memory instead of env variable

Could you please consider adding a runtime check for /dev/shm creation and add a fall back?

I see there is already a compile time switch to turn it off for Android, I would guess other embedded systems may have the same issue.
@EugeneZelenko EugeneZelenko added crash Prefer [crash-on-valid] or [crash-on-invalid] openmp and removed new issue labels Feb 20, 2022
@llvmbot
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llvmbot commented Feb 20, 2022

@llvm/issue-subscribers-openmp

@jdoerfert
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@AndreyChurbanov WDYT, can we check and use a tmp folder in case it's not available?

@AndreyChurbanov
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can we check and use a tmp folder in case it's not available?
@jdoerfert I think you are right. This sound better than fallback to using (potentially unsafe) environment variable.
If nobody jumps in, I will work on a patch in a week or so.

@stuartmcmahon-h3d
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/tmp is available on AWS Lambda so would definitely work for us.

If the intent of the startup & shutdown code is to handle openMP versioning then a long term solution may be to remove it and let clients handle versioning themselves. Though I realise that is not backwards compatible.

@guillaumekln guillaumekln mentioned this issue Sep 23, 2022
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@shiltian shiltian self-assigned this Jan 19, 2023
CarlosAlbertoEnciso pushed a commit to SNSystems/llvm-debuginfo-analyzer that referenced this issue Jan 25, 2023
@shiltian @CarlosAlbertoEnciso
[OpenMP] Create a temp file in /tmp if /dev/shm is not accessible
323b434 
When `libomp` is initialized, it creates a temp file in `/dev/shm` to store
registration flag. Some systems, like Android, don't have `/dev/shm`, then this
feature is disabled by the macro `KMP_USE_SHM`, though most Linux distributions
have that. However, some customized distribution, such as the one reported in
llvm/llvm-project#53955, doesn't support it either.
It causes a core dump. In this patch, if it is the case, we will try to create a
temporary file in `/tmp`, and if it still doesn't make it, then we error out.
Note that we don't consider in this patch if the temporary directory has been
set to `TMPDIR` in this patch. If `/tmp` is not accessible, we error out.

Fix #53955.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D142175
@bennyhawk bennyhawk mentioned this issue Dec 22, 2023
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@jdoerfert @shiltian @EugeneZelenko @AndreyChurbanov @llvmbot @stuartmcmahon-h3d