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mq_overview.7: Document QSIZE bug that appeared in 3.5 and was fixed in 4.2 

Reported-by: Arto Bendiken <arto@bendiken.net>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2015-08-09 13:17:14 +02:00
parent 98955680b3
commit a58feaee8b
1 changed files with 15 additions and 1 deletions
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man7/mq_overview.7
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@ -315,7 +315,7 @@ QSIZE:129 NOTIFY:2 SIGNO:0 NOTIFY_PID:8260
These fields are as follows:
.TP
.B QSIZE
Number of bytes of data in all messages in the queue.
Number of bytes of data in all messages in the queue (but see BUGS).
.TP
.B NOTIFY_PID
If this is nonzero, then the process with this PID has used
@ -373,6 +373,20 @@ limit could be raised,
and the ceiling was enforced even for privileged processes.
This ceiling value was removed in Linux 3.14,
and patches to stable kernels 3.5.x to 3.13.x also removed the ceiling.
As originally implemented (and documented),
the QSIZE field displayed the total number of (user-supplied)
bytes in all messages in the message queue.
Some changes in Linux 3.5
.\" commit d6629859b36d
inadvertently changed the behavior,
so that this field also included a count of kernel overhead bytes
used to store the messages in the queue.
This behavioral regression was rectified in Linux 4.2
.\" commit de54b9ac253787c366bbfb28d901a31954eb3511
(and earlier stable kernel series),
so that the count once more included just the bytes of user data
in messages in the queue.
.SH SEE ALSO
.BR getrlimit (2),
.BR mq_getsetattr (2),