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FREEMSG

Section: Linux Fast-STREAMS DDI/DKI (9)
Updated: 2008-10-31
Index Return to Main Contents

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NAME

freemsg - frees a STREAMS message

SYNOPSIS

#include <sys/stream.h>

void freemsg(mblk_t *mp);

ARGUMENTS

mp

the message to free.

INTERFACE

STREAMS.

DESCRIPTION

freemsg() frees the STREAMS(4) message pointed to by mp and the associated message blocks, data blocks and data buffers.

Freeing the message blocks of the message might or might not result in the deallocation of the message blocks, data blocks or data buffers, depending upon the internal implementation, the binding of message blocks to data blocks and whether the buffers are internal or external buffers.

For external data buffers that are to be freed, the function will be called with the arg provided previously to a esballoc(9) call.

RETURN

freemsg() returns void.

ERRORS

If the block pointer, bp, passed to freeb() is NULL, then freeb() will silently fail.

CONTEXT

freemsg() can be called from any context, including user context, module procedures, callouts, callbacks, soft interrupts (tasklets and bottom halves), and interrupt service routines.

MP-STREAMS

freemsg() is MP-safe. It is the caller's responsibility to ensure that it has the last remaining reference to the message blocks in the passed in message.

IMPLEMENTATION

freemsg() is implemented with a looping call to freeb(9), following along the b_cont pointer of each message block in the message block chain beginning with the passed in message block, mp.

See freeb(9) for more information.

SEE ALSO

allocb(9), esballoc(9) and freeb(9).

BUGS

freemsg() has no known bugs.

COMPATIBILITY

freemsg() is compatible with SVR 4.2 MP DDI/DKI[1], and implementations based on SVR 4[2] with the following portability considerations:

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See freeb(9) for additional compatibility information.

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In addition, LiS[3] uses a free list to hold freed message blocks and data blocks. It is particularly inefficient for cache performance to do this. LiS[3] should use kernel memory caches instead and should free the message blocks and data blocks when they are no longer used to allow existing cache slots to be reused. Bypassing the kernel memory allocation and deallocation mechanisms by using a free list results in poorer performance than might be expected by those that do not understand kernel memory caching mechanisms.

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Binary compatibility is not guaranteed.

See STREAMS(9) for additional compatibility information.

CONFORMANCE

SVR 4.2 MP DDI/DKI[1].

HISTORY

freemsg() appears as part of SVR 4.0 STREAMS[4].

freemsg() appeared first in SVR 3[5].

REFERENCES

[1]

USL DDI/DKI, Device Driver Interface/Driver-Kernel Interface (DDI/DKI) Reference Manual for Intel Processors, 1992, (Englewood Cliffs, New Jersey), AT&T UNIX System Laboratories, Inc., Prentice Hall.

[2]

SVR 4 DDI/DKI, UNIX® System V Release 4 Device Driver Interface/Driver-Kernel Interface (DDI/DKI) Reference Manual, 1990, (Englewood Cliffs, New Jersey), AT&T UNIX System Laboratories, Inc., Prentice Hall.

[3]

LIS 2.18, Linux STREAMS (LiS) 2.18.6 Source Code, Brian Bidulock, ed., OpenSS7 Corporation. <http://www.openss7.org/>

[4]

SVR 4, UNIX® System V Release 4 STREAMS Programmer's Guide, 1990, (Englewood Cliffs, New Jersey), AT&T UNIX System Laboratories, Inc., Prentice Hall.

[5]

SVR 3, UNIX® System V Release 3 STREAMS Programmer's Guide, (Englewood Cliffs, New Jersey), AT&T UNIX System Laboratories, Inc., Prentice Hall.

TRADEMARKS

OpenSS7tm

is a trademark of OpenSS7 Corporation.

Linux®

is a registered trademark of Linus Torvalds.

UNIX®

is a registered trademark of The Open Group.

Solaris®

is a registered trademark of Sun Microsystems.

Other trademarks are the property of their respective owners.

IDENTIFICATION

Linux Fast-STREAMS: Package streams version 0.9.2.4 released 2008-10-31.

Copyright©1997-2008OpenSS7 Corp. All Rights Reserved.
(See roff source for permission notice.)

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Index

NAME

SYNOPSIS

ARGUMENTS

INTERFACE

DESCRIPTION

RETURN

ERRORS

CONTEXT

MP-STREAMS

IMPLEMENTATION

SEE ALSO

BUGS

COMPATIBILITY

CONFORMANCE

HISTORY

REFERENCES

TRADEMARKS

IDENTIFICATION

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