RamSemStruc

Pointers

TCB_SemInfo
Locations
Multiple, in user storage.
VM Owner
Multipl user storage owners.

Format

┌─────────────────────────┬────────┬────────┬────────┬────────────────────────────────────────┐│Field Name               │Off     │Length  │Type    │Description                             │
├─────────────────────────┼────────┼────────┼────────┼────────────────────────────────────────┤
│RamSemStruc              │+0      │4       │S       │Ram Semaphore                           │
├─────────────────────────┼────────┼────────┼────────┼────────────────────────────────────────┤
│RamSemOwner              │+0      │1       │B       │Ownership flag                          │
├─────────────────────────┼────────┼────────┼────────┼────────────────────────────────────────┤
│RamSemFlag               │+1      │1       │B       │Ram Semaphore flag bit field            │
├─────────────────────────┼────────┼────────┼────────┼────────────────────────────────────────┤
│RamSemID                 │+2      │2       │W       │RamSem Block/Run ID low word            │
└─────────────────────────┴────────┴────────┴────────┴────────────────────────────────────────┘

RamSemFlag definitions

┌──────────────────┬─────┬────────────────────────────────────────┐
│name              │value│description                             │
├──────────────────┼─────┼────────────────────────────────────────┤
│RAMSEM_WAITING    │0x01 │a thread is waiting on the sem          │
├──────────────────┼─────┼────────────────────────────────────────┤
│RAMSEM_MUXWAITING │0x02 │a thread is muxwaiting on the sem       │
└──────────────────┴─────┴────────────────────────────────────────┘

Notes:

The high-order 4 bit of the RamSemFlag are used as an extended owner field (to cater for more than 512 threads).

Only kernel code sets the RamSemOwner field to a thread slot number. Ring 3 RamSems have 0xff value for an owned RamSem

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