Miscellaneous Functions and Constants

Declared in: be/kernel/OS.h (unless otherwise noted)

Functions

clear_caches()

Declared in: be/kernel/image.h

	void clear_caches(void *addr, size_t len, uint32 flags)

This function clears or invalidates the instruction and data caches. You should only need this function if you're generating code on the fly, or if you're performing a timing loop and you want to start with fresh caches (to get a "worst case" estimate).

The argument are:

• addr is the starting address of a section of memory that corresponds to a section of one of the caches.

• len is the length, in bytes, of the instruction or data segment that you want to clear or invalidate.

• flags is one or both of B_INVALIDATE_ICACHE and B_FLUSH_DCACHE.

By invalidating a section of the instruction cache, you cause the instructions in that section to be reloaded next time they're needed. Flushing the data cache causes the in-memory copy of the data to be written out to the cache.

debugger()

	void debugger(const char *string)

Throws the calling thread into the debugger. The string argument becomes the debugger's first utterance.

disable_debugger()

	int disable_debugger(int state)

Instructs the kernel to send a signal for all exceptions, even those that don't normally trigger the debugger. If the application doesn't have a handler installed for the exception, the team dies without triggering the debugger. state should be nonzero to turn on this functionality or 0 to turn it off.

set_alarm()

	bigtime_t set_alarm(bigtime_t time, uint32 mode)

Tells the kernel to send the SIGALRM signal at some point in the future, as defined by the arguments:

• If mode is B_PERIODIC_ALARM, the signal is sent every time microseconds, starting as soon as set_alarm() function returns.

• If mode is B_ONE_SHOT_ABOLUTE_ALARM, the signal is sent once (only) after time microseconds have elapsed measured from the time the system was booted. If that point has already passed, the signal is sent immediately.

• If mode is B_ONE_SHOT_RELATIVE_ALARM, the signal is sent once (only) after time microseconds have elapsed from the time set_alarm() returns.

When the signal is sent, the SIGALRM handler is called (you set the handler through the normal means, by calling the Posix signal() function). The handler runs in the thread that set the alarm.

From within the SIGALRM handler, you mustn't call anything that would cause the kernel scheduler to run. Just about the only safe call you can make from your signal handler is release_sem().

The most recent alarm requested cancels any previous request. For example, in this sequence...

   /* Ask for an alarm ten seconds from now. */
   set_alarm(10e6, B_ONE_SHOT_RELATIVE_ALARM); 
   /* Ask for an alarm one second from now. */
   set_alarm(10e5, B_ONE_SHOT_RELATIVE_ALARM); 

...only the second alarm request will be fulfilled—the first requested is cancelled when the second set_alarm() call is made. This applies to all alarm types; for example, a one-shot alarm request will cancel an active periodic alarm.

To explicitly cancel the previous alarm request without installing a new alarm, do this:

   set_alarm(B_INFINITE_TIMEOUT, B_PERIODIC_ALARM);

This cancels the previous alarm request regardless of the type of alarm.

set_signal_stack()

Declared in: posix/signal.be.h

	void set_signal_stack(void *ptr, size_t size)

Sets the location and size of the stack that's used by the thread's signal handlers.

Constants

B_INFINITE_TIMEOUT

	B_INFINITE_TIMEOUT

The inifinite timeout value can be used to specify, to timeout-accepting functions, that you're willing to wait forever.

B_OS_NAME_LENGTH

	B_OS_NAME_LENGTH

This constant gives the maximum length of the name of a thread, semaphore, port, area, or other operating system bauble.

B_PAGE_SIZE

	B_PAGE_SIZE

The B_PAGE_SIZE constant gives the size, in bytes, of a page of RAM.