[Bug 2136] New: Race condition in _Thread_Change_priority() with most schedulers

[bugzilla-daemon at rtems.org]

https://www.rtems.org/bugzilla/show_bug.cgi?id=2136

             Bug #: 2136
           Summary: Race condition in _Thread_Change_priority() with most
                    schedulers
    Classification: Unclassified
           Product: RTEMS
           Version: HEAD
          Platform: All
        OS/Version: RTEMS
            Status: NEW
          Severity: normal
          Priority: P3
         Component: cpukit
        AssignedTo: joel.sherrill at oarcorp.com
        ReportedBy: sebastian.huber at embedded-brains.de


The call to rtems_task_suspend() is explicitly allowed in interrupt service
routines:

http://rtems.org/onlinedocs/doc-current/share/rtems/html/c_user/Interrupt-Manager-Directives-Allowed-from-an-ISR.html#Interrupt-Manager-Directives-Allowed-from-an-ISR

Suppose a thread changes its priority.  It will end up in
_Thread_Change_priority().

The first action is  _Thread_Set_transient( the_thread ).  Suppose an ISR
happens after this action which suspends this thread.  It will add
STATES_SUSPENDED to the threads state.

Now back in _Thread_Change_priority() line 61 we have state != STATES_TRANSIENT
and we exit the function without additional scheduler operations.

Now we have a thread executing with STATES_SUSPENDED set with most schedulers
since they don't update the heir and thread dispatch necessary in their extract
operation.

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