Tornado

6
Browser
Figure 6-27
At this point examining the code (not shown) may seem worthwhile. Doing so,
you notice that uMed uses no shared resources, but uHi and uLow synchronize
their work with a semaphore.
Examining the semaphore with the browser (Figure 6-27) confirms the dawning
suspicion: uHi is indeed blocking on the semaphore, which uLow cannot release
because uMed has preempted it.
uHi Blocked on Semaphore
6
Having diagnosed the problem as a classic priority inversion, the fix is
straightforward. As described in VxWorks Programmer’s Guide: Basic OS, you can
revise the application to synchronize uLow and uHi with a mutual-exclusion
semaphore created with the SEM_INVERSION_SAFE option.
6.13 Tcl: the Browser Initialization File
When the browser begins executing, it first checks for a file called
.wind/browser.tcl in your home directory. If this file exists, its contents are sourced
as Tcl code.
For example, it may be convenient to download object modules from the browser.
The following browser.tcl code defines a button and a procedure to implement
this.
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