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<div class="moz-cite-prefix">On 13/04/2022 06.56, [EXT] 王斌 wrote:<br>
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cite="mid:a93f01134ae0421487af7c9dfd8c3893@ylex-mbx04.yealink.com">
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<p class="MsoNormal"><span lang="EN-US">Hi</span>：<span
lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">See lock_hash in
h_table.c:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Flowing lines of code do
not guarantee atomicity and I think it is not safe:<o:p></o:p></span></p>
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<!--[if !supportLists]--><span lang="EN-US"><span
style="mso-list:Ignore">-<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span lang="EN-US">atomic_get(&_tm_table->entries[i].locker_pid)
!= mypid<o:p></o:p></span></p>
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<!--[if !supportLists]--><span lang="EN-US"><span
style="mso-list:Ignore">-<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span lang="EN-US">lock(&_tm_table->entries[i].mutex)<o:p></o:p></span></p>
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<!--[if !supportLists]--><span lang="EN-US"><span
style="mso-list:Ignore">-<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span lang="EN-US">atomic_set(&_tm_table->entries[i].locker_pid,
mypid)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p>Not my code, but I would say it is safe, because the only race
condition you could possibly encounter where it would make a
difference is when atomic_get(&locker_pid) returns a value
other than mypid (true condition) and is then subsequently set to
mypid by a different thread before the mutex can be acquired
(flipping the condition to false), which cannot happen because all
threads have different PIDs.</p>
<p>Cheers<br>
</p>
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