This issue looks similar to Bug ID -- 757162. So, merging the issue into same.
Thank You.

ClusterFuzz has detected this issue as fixed in range 502042:502043.

Detailed report: https://clusterfuzz.com/testcase?key=5568827730690048

Fuzzer: tokenfuzz_pdf_april16
Job Type: linux_tsan_chrome_mp
Platform Id: linux

Crash Type: Data race ATOMIC READ 1
Crash Address: 0x7b0c0004f260
Crash State:
  pthread_mutex_lock
  pa_mutex_lock
  pa_xmalloc
  
Sanitizer: thread (TSAN)

Regressed: https://clusterfuzz.com/revisions?job=linux_tsan_chrome_mp&range=471546:471559
Fixed: https://clusterfuzz.com/revisions?job=linux_tsan_chrome_mp&range=502042:502043

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5568827730690048

See https://github.com/google/clusterfuzz-tools for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

ClusterFuzz has detected this issue as fixed in range 502656:502679.

Detailed report: https://clusterfuzz.com/testcase?key=5568827730690048

Fuzzer: tokenfuzz_pdf_april16
Job Type: linux_tsan_chrome_mp
Platform Id: linux

Crash Type: Data race ATOMIC READ 1
Crash Address: 0x7b0c0004f260
Crash State:
  pthread_mutex_lock
  pa_mutex_lock
  pa_xmalloc
  
Sanitizer: thread (TSAN)

Regressed: https://clusterfuzz.com/revisions?job=linux_tsan_chrome_mp&range=471546:471559
Fixed: https://clusterfuzz.com/revisions?job=linux_tsan_chrome_mp&range=502656:502679

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5568827730690048

See https://github.com/google/clusterfuzz-tools for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.