IV78991: PARTIALLY FILLED PAGES IN SHARED CLASS CACHE ARE NOT WRITE PROTE CTED

APAR status

• Closed as program error.

Error description

• Error Message: N/A
  .
  Stack Trace: N/A
  .
  

Local fix

• N/A
  

Problem summary

• When JVM adds data to shared class cache, it marks the pages
  read-only when the whole page is filled with data. Partially
  filled pages thus remain write-able unless they are completely
  filled up, and may be corrupted.
  

Problem conclusion

• JVM has been updated to memory protect partially filled pages in
  the shared class cache. By default (that is when
  -Xshareclasses:mprotect is not specified or
  -Xshareclasses:mprotect=default is specified) after JVM startup
  phase is over, whenever new data is to be added to the shared
  class cache, JVM first changes the memory protection of any
  partially filled pages to read-write, adds data to the cache,
  and then changes the memory protection of any partially filled
  pages to read-only.
  To provide more control on memory protection of partially filled
  pages, following -Xshareclasses options have been added:
  -Xshareclasses:mprotect=onfind This option protects partially
  filled pages when JVM reads new data in the cache added by other
  JVM.
  -Xshareclasses:mprotect=nopartialpages This option disables
  memory protection of partially filled pages. JVM would protect
  only those pages which are completely full. (Previous default)
  -Xshareclasses:mprotect=partialpagesonstartup By default JVM
  performs memory protection of partially filled pages after
  startup phase is over. This option enables memory protection of
  partially filled pages since JVM startup.
  These change are applicable to Linux and Windows operating
  system only.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR2 FP10  (8.0.2.10)
     7    SR9 FP30  (7.0.9.30)
     6 R1 SR8 FP20  (6.1.8.20)
     7 R1 SR3 FP30  (7.1.3.30)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  Service Refreshes and Fix Packs can be found at:
             https://www.ibm.com/developerworks/java/jdk/
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  J9 COMMON CODE

• Fixed component ID

  620700127

Applicable component levels

• R270 PSY

     UP

• R260 PSY

     UP