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)
Check Out this Related Man Page
pthread_mutexattr_getprotocol(3C) Standard C Library Functions pthread_mutexattr_getprotocol(3C)NAME
pthread_mutexattr_getprotocol, pthread_mutexattr_setprotocol - get or set protocol attribute of mutex attribute object
SYNOPSIS
cc -mt [ flag... ] file... -lpthread [ library... ]
#include <pthread.h>
int pthread_mutexattr_getprotocol(
const pthread_mutexattr_t *restrict attr,
int *restrict protocol);
int pthread_mutexattr_setprotocol(pthread_mutexattr_t *attr,
int protocol);
DESCRIPTION
The pthread_mutexattr_setprotocol() and pthread_mutexattr_getprotocol() functions, respectively, set and get the protocol attribute of a
mutex attribute object pointed to by attr, which was previously created by the pthread_mutexattr_init() function.
The protocol attribute defines the protocol to be followed in utilizing mutexes. The value of protocol may be one of PTHREAD_PRIO_NONE,
PTHREAD_PRIO_INHERIT, or PTHREAD_PRIO_PROTECT, which are defined by the header <pthread.h>.
When a thread owns a mutex with the PTHREAD_PRIO_NONE protocol attribute, its priority and scheduling are not affected by its mutex owner-
ship.
When a thread is blocking higher priority threads because of owning one or more mutexes with the PTHREAD_PRIO_INHERIT protocol attribute,
it executes at the higher of its priority or the priority of the highest priority thread waiting on any of the mutexes owned by this thread
and initialized with this protocol.
When a thread owns one or more mutexes initialized with the PTHREAD_PRIO_PROTECT protocol, it executes at the higher of its priority or the
highest of the priority ceilings of all the mutexes owned by this thread and initialized with this attribute, regardless of whether other
threads are blocked on any of these mutexes.
While a thread is holding a mutex that has been initialized with the PRIO_INHERIT or PRIO_PROTECT protocol attributes, it will not be sub-
ject to being moved to the tail of the scheduling queue at its priority in the event that its original priority is changed, such as by a
call to sched_setparam(). Likewise, when a thread unlocks a mutex that has been initialized with the PRIO_INHERIT or PRIO_PROTECT protocol
attributes, it will not be subject to being moved to the tail of the scheduling queue at its priority in the event that its original prior-
ity is changed.
If a thread simultaneously owns several mutexes initialized with different protocols, it will execute at the highest of the priorities that
it would have obtained by each of these protocols.
If a thread makes a call to pthread_mutex_lock() for a mutex that was initialized with the protocol attribute PTHREAD_PRIO_INHERIT, and if
the calling thread becomes blocked because the mutex is owned by another thread, then the owner thread inherits the priority level of the
calling thread for as long as it continues to own the mutex. The implementation updates its execution priority to the maximum of its
assigned priority and all its inherited priorities. Furthermore, if this owner thread becomes blocked on another mutex, the same priority
inheritance effect will be propagated to the other owner thread, in a recursive manner.
A thread that uses mutexes initialized with the PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT protocol attribute values should have its
scheduling policy equal to SCHED_FIFO or SCHED_RR (see pthread_attr_getschedparam(3C) and pthread_getschedparam(3C)).
If a thread with scheduling policy equal to SCHED_OTHER uses a mutex initialized with the PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT pro-
tocol attribute value, the effect on the thread's scheduling and priority is unspecified.
The _POSIX_THREAD_PRIO_INHERIT and _POSIX_THREAD_PRIO_PROTECT options are designed to provide features to solve priority inversion due to
mutexes. A priority inheritance or priority ceiling mutex is designed to minimize the dispatch latency of a high priority thread when a low
priority thread is holding a mutex required by the high priority thread. This is a specific need for the realtime application domain.
Threads created by realtime applications need to be such that their priorities can influence their access to system resources (CPU
resources, at least), in competition with all threads running on the system.
RETURN VALUES
Upon successful completion, the pthread_mutexattr_getprotocol() and pthread_mutexattr_setprotocol() functions return 0. Otherwise, an
error number is returned to indicate the error.
ERRORS
The pthread_mutexattr_getprotocol() and pthread_mutexattr_setprotocol() functions will fail if:
EINVAL The value specified by attr is NULL.
ENOSYS Neither of the options _POSIX_THREAD_PRIO_PROTECT and _POSIX_THREAD_PRIO_INHERIT is defined and the system does not support the
function.
ENOTSUP The value specified by protocol is an unsupported value.
The pthread_mutexattr_getprotocol() and pthread_mutexattr_setprotocol() functions may fail if:
EINVAL The value specified by attr or protocol is invalid.
EPERM The caller does not have the privilege to perform the operation.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Committed |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
|Standard |See standards(5). |
+-----------------------------+-----------------------------+
SEE ALSO pthread_attr_getschedparam(3C), pthread_mutex_init(3C), pthread_mutexattr_init(3C), sched_setparam(3C), sched_setscheduler(3C),
attributes(5), standards(5)SunOS 5.11 5 Feb 2008 pthread_mutexattr_getprotocol(3C)