[RT BUG] Mismatched get_uid/free_uid usage in signals in some rts (2nd try)

[Joe Korty]

Mismatched get_uid/free_uid usage in signals in 4.9.312-rt193

     [  First attempt using mutt did not show up on the mailing lists.
        Trying again with office365 Outlook.   Also added the 4.9-rt
        maintainers. ]

The 4.19-rt patch,

   0329-signal-Prevent-double-free-of-user-struct.patch

needs to be ported to LAG 4.9-rt, as that release now has the Linus commit,

   fda31c50292a ("signal: avoid double atomic counter increments for user accounting")

which breaks the longstanding rt patch,

   0259-signals-Allow-rt-tasks-to-cache-one-sigqueue-struct.patch

Current application status:

   4.4.302-rt232        OK      has both Linus's patch and the fix needed for rt.
   4.9.312-rt193        BROKE   has Linus's patch but not the fix.
   4.14.87-rt50         OK      does NOT have either Linus's patch nor its rt fix.
   4.19.246-rt110       OK      has both Linus's patch and the fix needed for rt.
   5.4.193-rt74         OK	has both Linus's patch and the fix needed for rt.
   5.10.120-rt70        OK	has both Linus's patch and the fix needed for rt.
   5.15.44-rt46         UNKNOWN no get_uid/free_uid usage in kernel/signal.c anymore.

Regards,
Joe