pi_stress(8) [debian man page]

pi_stress(8)						Linux System Administrator's Manual					      pi_stress(8)

NAME

       pi_stress - a stress test for POSIX Priority Inheritance mutexes

SYNOPSIS

       pi_stress  [-i|--inversions  inversions]  [-t|--duration  seconds]  [-g|--groups groups [-d|--debug] [-v|--verbose] [-s|--signal] [-r|--rr]
       [-p|--prompt] [-m|--mlockall] [-u|--uniprocessor]
       pi_stress -h|--help

DESCRIPTION

       pi_stress is a program used to stress the priority-inheritance code paths for POSIX mutexes, in both the Linux kernel and the C library. It
       runs  as  a  realtime-priority task and launches inversion machine thread groups. Each inversion group causes a priorty inversion condition
       that will deadlock if priority inheritance doesn't work.

OPTIONS

       -i n|--inversions=n
	      Run for n number of inversion conditions. This is the total number of inversions for all inversion groups. Default is -1	for  infi-
	      nite.

       -t n|--duration=n
	      Run the test for n seconds and then terminate.

       -g n|--groups=n
	      The number of inversion groups to run. Defaults to 10.

       -d|--debug
	      Run in debug mode; lots of extra prints

       -v|--verbose
	      Run with verbose messages

       -s|--signal
	      Terminate on receipt of SIGTERM (Ctrl-C). Default is to terminate on any keypress.

       -r|--rr
	      Run inversion group threads as SCHED_RR (round-robin). The default is to run the inversion threads as SCHED_FIFO.

       -p|--prompt
	      Prompt before actually starting the stress test

       -u|--uniprocessor
	      Run  all threads on one processor. The default is to run all inversion group threads on one processor and the admin threads (report-
	      ing thread, keyboard reader, etc.) on a different processor.

       -m|--mlockall
	      Call mlockall to lock current and future memory allocations and prevent being paged out

       -h|--help
	      Display a short help message and options.

CAVEATS

       The pi_stress test threads run as SCHED_FIFO or SCHED_RR threads, which means that they can starve critical system threads. It is advisable
       to  change the scheduling policy of critical system threads to be SCHED_FIFO prior to running pi_stress and use a priority of 10 or higher,
       to prevent those threads from being starved by the stress test.

BUGS

       No documented bugs.

AUTHOR

       Clark Williams <williams@redhat.com>

								   Nov 27, 2006 						      pi_stress(8)

pthread_rwlock_trywrlock(3)				     Library Functions Manual				       pthread_rwlock_trywrlock(3)

NAME

       pthread_rwlock_trywrlock - Attempts to acquire a read-write lock for write access without waiting.

LIBRARY

       DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS

       #include <pthread.h>

       int   pthread_rwlock_trywrlock(
			     pthread_rwlock_t	      *rwlock);

PARAMETERS

       Address of the read-write lock object to acquire for write access.

DESCRIPTION

       This routine attempts to acquire the read-write lock referenced by rwlock for write access. If any thread already holds that lock for write
       access or read access, this routine fails and returns [EBUSY] and the calling thread does not wait for the lock to become available.

       Results are undefined if the calling thread holds the read-write lock (whether for read or write  access)  at  the  time  this  routine	is
       called.

       If the read-write lock object referenced by rwlock is not initialized, the results of calling this routine are undefined.

       Realtime applications can encounter priority inversion when using read-write locks. The problem occurs when a high-priority thread acquires
       a read-write lock that is about to be unlocked (that is, posted) by a low-priority thread, but the low-priority thread is  preempted  by  a
       medium-priority thread.	This scenario leads to priority inversion  in that a high-priority thread is blocked by lower-priority threads for
       an unlimited period of time.  During system design, realtime programmers must take into account the possibility of priority  inversion  and
       can  deal with it in a number of ways, such as by having critical sections that are guarded by read-write locks execute at a high priority,
       so that a thread cannot be preempted while executing in its critical section.

RETURN VALUES

       If an error condition occurs, this routine returns an integer value indicating the type of error.  Possible return values are  as  follows:
       Successful  completion.	 The  read-write lock could not be acquired for write access because it was already locked for write access or for
       read access.  The value specified by rwlock does not refer to an initialized read-write lock object.  The current thread already  owns  the
       read-write lock for write or read access.

ERRORS

       None

RELATED INFORMATION

       Functions: pthread_rwlock_init(3), pthread_rwlockattr_init(3), pthread_rwlock_rdlock(3), pthread_rwlock_wrlock(3), pthread_rwlock_unlock(3)

       Manuals: Guide to DECthreads and Programmer's Guide

       delim off

														       pthread_rwlock_trywrlock(3)