Making Sure No Other Threads Are Running

assert(NO_COMPETING_THREADS);

LockLint recognizes this assertion to mean that, when this point in the code is reached, no other threads should be competing with the one running this code. Violations (based on information provided by certain NOTE-style assertions) are reported during analysis. Any function that accesses variables without holding their protecting locks (operating under the assumption that no other relevant threads are out there touching the same data), should be so marked.

By default, this assertion is ignored at runtime--that is, it always succeeds. No generic runtime meaning for NO_COMPETING_THREADS is possible, since the notion of which threads compete involves knowledge of the application. For example, a driver might make such an assertion to say that no other threads are running in this driver for the same device. Because no generic meaning is possible, synch.h defines NO_COMPETING_THREADS as 1 if it has not already been otherwise defined.

However, you can override the default meaning for NO_COMPETING_THREADS by defining it before including either note.h or synch.h (which may be included in either order). For example, if the program keeps a count of the number of running threads in a variable called num_threads, the following definition might suffice:

#define NO_COMPETING_THREADS (num_threads == 1)
#include <note.h>
#include <synch.h>

Doing so does not affect LockLint's testing of the assertion.