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The byte allocate records a trace event on the way in, saves the entry's time
stamp, and comes back to write the address it returned into that same entry --
but only if the time stamp says nothing overwrote the entry meanwhile. Nothing
in the kernel writes a trace event inside the window, so the other arm had no
agent and no test.
The Linux SMP port's TX_BYTE_ALLOCATE_EXTENSION gains a second clause, guarded
by its own flag and calling a routine the harness declares weakly, in the shape
TX_BYTE_RELEASE_EXTENSION already uses. The hook runs between the restore and
the disable that bracket the pool search, which on SMP is a real release of the
protection rather than an interrupt gap. A new test filters the byte pool event
class so the allocate's own insert writes nothing and leaves the buffer parked
on the saved entry, then lets the hook write a user event onto it; neither lever
reaches the arm without the other. No kernel symbol is replaced and the allocate
runs its own code end to end. The macro expands inside tx_byte_allocate.c, so
the new clause's if is certified-source branch: the union branch denominator
moves from 3610 to 3612 and both new outcomes are covered.
The arm closes in trace_build alone. Under TX_MISRA_ENABLE the port's trace time
source returns a constant, so the comparison reads 0 == 0 whatever the hook
writes, and the test asserts the consequence only where the time source is real.
135/135 in each of eight configurations, 3586/3612 branch outcomes on the union
basis against 3583/3610 before. Fifty standalone repeats in each of the eight,
no failures.
Assisted-by: Claude Code (Opus 5) <[email protected]>
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