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__init_tp: Initialize TID to non-zero value #360

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@yamt yamt commented Dec 13, 2022

__init_tp: Initialize TID to non-zero value

This fixes TID-based locking used within libc.

Also, initialize detach_state.

cf. WebAssembly/wasi-threads#16

* - __lockfile relies on the fact the most significant two bits
* of TIDs are 0.
*/
td->tid = 0x3fffffff;
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Initialize the TID to a large value, which is hopefully
less likely to conflict with host-allocated TIDs

So, that assumption is correct only if the host assigns the ID incrementally, which might not be the case (host can decide the implementation).

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Initialize the TID to a large value, which is hopefully
less likely to conflict with host-allocated TIDs

So, that assumption is correct only if the host assigns the ID incrementally, which might not be the case (host can decide the implementation).

right. this is a kludge at best.

i think a real fix involves spec changes. see WebAssembly/wasi-threads#15

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I'd suggest let's wait with this PR then until the WebAssembly/wasi-threads#15 is resolved

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I think we can update the PR based on the discussion in WebAssembly/wasi-threads#15 @yamt ?

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I think we can update the PR based on the discussion in WebAssembly/wasi-threads#15 @yamt ?

done

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wpoynter Will Poynter
This fixes TID-based locking used within libc.

Also, initialize detach_state.

cf. WebAssembly/wasi-threads#16
@yamt yamt changed the title __init_tp: Workaround TID issue __init_tp: Initialize TID to non-zero value Jan 4, 2023
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yamt commented Jan 4, 2023

i updated the comment after WebAssembly/wasi-threads#16

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I think this is fine; I would want to link to the wasi-threads heading where this is discussed, but that's personal preference.

@abrown abrown merged commit 5a255d5 into WebAssembly:main Jan 6, 2023
john-sharratt pushed a commit to john-sharratt/wasix-libc that referenced this pull request Mar 6, 2023

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wpoynter Will Poynter
This fixes TID-based locking used within libc.

Also, initialize detach_state.

cf. WebAssembly/wasi-threads#16
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3 participants