Advanced Programming in the UNIX® Environment

ptg10805159

426 Thread Control Chapter 12

Name of limit Description nameargument

PTHREAD_DESTRUCTOR_ITERATIONS maximum number of times an _SC_THREAD_DESTRUCTOR_ITERATIONS

implementation will try to

destroy the thread-specific

data when a thread exits

(Section 12.6)

PTHREAD_KEYS_MAX maximum number of keys that can_SC_THREAD_KEYS_MAX

be created by a process

(Section 12.6)

PTHREAD_STACK_MIN minimum number of bytes that can_SC_THREAD_STACK_MIN

be used for a thread’s stack

(Section 12.3)

PTHREAD_THREADS_MAX maximum number of threads that _SC_THREAD_THREADS_MAX

can be created in a process

(Section 12.3)

Figure 12.1 Thread limits andnamearguments tosysconf

Figure12.2 shows the values of the thread limits for the four implementations

described in this book. If the implementation’s limit is indeterminate, ‘‘no limit’’is

listed. This doesn’t mean that the value is unlimited, however.

Note that although an implementation may not provide access to these limits, that doesn’t

mean that the limits don’t exist. It just means that the implementation doesn’t provide us with

away to get at them usingsysconf.

FreeBSD Linux Mac OS X Solaris

Limit 8.0 3.2.0 10.6.8 10

PTHREAD_DESTRUCTOR_ITERATIONS 444 no limit

PTHREAD_KEYS_MAX 256 1,024 512 no limit

PTHREAD_STACK_MIN 2,048 16,384 8,192 8,192

PTHREAD_THREADS_MAX no limit no limit no limit no limit

Figure 12.2Examples of thread configuration limits

12.3 Thread Attr ibutes

The pthread interface allows us to fine-tune the behavior of threads and

synchronization objects by setting various attributes associated with each object.

Generally,the functions for managing these attributes follow the same pattern:

1. Each object is associated with its own type of attribute object (threads with
   thread attributes, mutexes with mutex attributes, and so on). An attribute object
   can represent multiple attributes. The attribute object is opaque to applications.
   This means that applications aren’t supposed to know anything about its
   internal structure, which promotes application portability.Instead, functions
   areprovided to manage the attributes objects.