<html>
    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - tsan: false positives on shmat"
   href="https://bugs.llvm.org/show_bug.cgi?id=40282">40282</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>tsan: false positives on shmat
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>compiler-rt
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>tsan
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>dvyukov@google.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Reported internally, don't have a public repro.
The crux: shmat/shmdt allocate/deallocate memory (like mmap/munmap). We don't
do anything in shmat/shmdt interceptors, so if the memory becomes reused across
shmat calls in different threads, tsan may report a false positive. Accesses to
the new mapping of the memory "race" with accesses to the old mapping at the
same address.
We need shmat/shmdt interceptors to do the same as mmap/munmap interceptors.
Probably the common code to "map" and "unmap" a range can be factored out.</pre>
        </div>
      </p>


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