cpu_switchto(9) [netbsd man page]

CPU_SWITCHTO(9) 					   BSD Kernel Developer's Manual					   CPU_SWITCHTO(9)

NAME

     cpu_switchto -- machine-dependent LWP context switching interface

SYNOPSIS

     #include <sys/cpu.h>

     lwp_t *
     cpu_switchto(lwp_t *oldlwp, lwp_t *newlwp, bool returning);

DESCRIPTION

     The cpu_switchto() function saves the context of the LWP which is currently running on the processor, and restores the context of the LWP
     specified by newlwp.

     Remarks:

	   1.	cpu_switchto() does not switch address spaces.

	   2.	cpu_switchto() sets curlwp(9) to newlwp.  If the architecture does non-interlocked adaptive mutex release, cpu_switchto() does an
		equivalent of membar_producer(3), before and after the modification of curlwp(9).

	   3.	cpu_switchto() should be called at IPL_SCHED.  When the function returns, the caller should lower the priority level as soon as
		possible.

	   4.	cpu_switchto() might be called with spin mutexes held.

     The function takes the following arguments.

	   oldlwp      Specify the LWP from which the switch is going to be made, i.e., the calling LWP.  If it was NULL, the context of the LWP
		       currently running on this processor is not saved.

	   newlwp      Specify the LWP to which to switch.  It must not be NULL.

	   returning   Only meaningful if the architecture implements fast software interrupts.  If true, it indicates that oldlwp is a soft
		       interrupt LWP that is blocking.	It is a good indication that any kind of address space or user activity can be completely
		       ignored.  For example: ras_lookup(9), cache flushes, TLB wirings, adjusting lazy FPU state.  All that is required is to
		       restore the register state and stack, and return to the interrupted LWP.

RETURN VALUES

     The cpu_switchto() function does not return until another LWP calls cpu_switchto().  It returns the oldlwp argument of the cpu_switchto()
     which is called to switch back to our LWP.  It is either a LWP which called cpu_switchto() to switch to us or NULL in case the LWP was exit-
     ing.

SEE ALSO

     membar_producer(3), swapcontext(3), intro(9), mutex(9), spl(9)

BSD
								   June 2, 2011 							       BSD

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_lwp_mutex_lock(2)						   System Calls 						_lwp_mutex_lock(2)

NAME

       _lwp_mutex_lock, _lwp_mutex_unlock, _lwp_mutex_trylock - mutual exclusion

SYNOPSIS

       #include <sys/lwp.h>

       int _lwp_mutex_lock(lwp_mutex_t *mp);

       int _lwp_mutex_trylock(lwp_mutex_t *mp);

       int _lwp_mutex_unlock(lwp_mutex_t *mp);

DESCRIPTION

       These  functions  serialize the execution of lightweight processes. They are useful for ensuring that only one lightweight process can exe-
       cute a critical section of code at any one time (mutual exclusion).  LWP mutexes must be initialized to 0 before use.

       The _lwp_mutex_lock() function locks the LWP mutex pointed to by mp. If the mutex is already locked, the calling LWP blocks until the mutex
       becomes available.  When _lwp_mutex_lock() returns, the mutex is locked and the calling LWP is the "owner".

       The  _lwp_mutex_trylock()  function  attempts  to  lock the mutex. If the mutex is already locked it returns with an error. If the mutex is
       unlocked, it is locked and _lwp_mutex_trylock() returns.

       The _lwp_mutex_unlock() function unlocks a locked mutex. The mutex must be locked and the calling LWP must be the one that last locked  the
       mutex (the owner). If any other LWPs are waiting for the mutex to become available, one of them is unblocked.

RETURN VALUES

       Upon successful completion, 0 is returned. A non-zero value indicates an error.

ERRORS

       If  any of the following conditions are detected, _lwp_mutex_lock(), _lwp_mutex_trylock(), and _lwp_mutex_unlock() fail and return the cor-
       responding value:

       EINVAL	       The mp argument points to an invalid LWP mutex.

       EFAULT	       The mp argument points to an illegal address.

       If any of the following conditions occur, _lwp_mutex_trylock() fails and returns the corresponding value:

       EBUSY	       The mp argument points to a locked mutex.

SEE ALSO

       intro(2), _lwp_cond_wait(2)

SunOS 5.10							    30 Jul 1992 						_lwp_mutex_lock(2)

Linux and UNIX Man Pages

cpu_switchto(9) [netbsd man page]

Check Out this Related Man Page