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mq_overview.7: Various fixes after review from Davidlohr Bueso 

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2014-10-02 23:05:47 +02:00
parent 94d6f75f52
commit fcd9822749
1 changed files with 18 additions and 37 deletions
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man7/mq_overview.7
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@ -151,15 +151,12 @@ is specified as NULL.
The default value for this file is 10.
The minimum and maximum are as for
.IR /proc/sys/fs/mqueue/msg_max .
If
.IR msg_default
exceeds
.IR msg_max ,
a new queue's default
A new queue's default
.I mq_maxmsg
value is capped to the
.I msg_max
limit.
value will be the smaller of
.IR msg_default
and
.IR msg_max .
Up until Linux 2.6.28, the default
.I mq_maxmsg
was 10;
@ -212,7 +209,7 @@ setting when the queue is created with a call to
where
.I attr
is specified as NULL.
The default value for this file is 8192.
The default value for this file is 8192 (bytes).
The minimum and maximum are as for
.IR /proc/sys/fs/mqueue/msgsize_max .
If
@ -270,36 +267,11 @@ number of message queues that can be created.
The default value for
.I queues_max
is 256.
The semantics of this limit have changed across kernel versions as follows:
.RS
.IP * 3
Before Linux 3.5,
this limit could be changed to any value in the range 0 to
.RB INT_MAX ,
but privileged processes
.RB ( CAP_SYS_RESOURCE )
can exceed the limit.
.IP * 3
Since Linux 3.5, there is a ceiling for this limit of 1024
.RB ( HARD_QUEUESMAX ).
Privileged processes
.RB ( CAP_SYS_RESOURCE )
can exceed the
No ceiling is imposed on the
.I queues_max
limit, but the
.BR HARD_QUEUESMAX
limit is enforced even for privileged processes.
.IP *
Starting with Linux 3.14,
.\" commit f3713fd9cff733d9df83116422d8e4af6e86b2bb
the
.B HARD_QUEUESMAX
ceiling is removed: no ceiling is imposed on the
.IR queues_max
limit, and privileged processes
limit; privileged processes
.RB ( CAP_SYS_RESOURCE )
can exceed the limit.
.RE
can exceed the limit (but see BUGS).
.SS Resource limit
The
.B RLIMIT_MSGQUEUE
@ -394,6 +366,15 @@ lists (ACLs) for POSIX message queues.
.SH EXAMPLE
An example of the use of various message queue functions is shown in
.BR mq_notify (3).
.SH BUGS
In Linux versions 3.5 to 3.14, the kernel imposed a ceiling of 1024
.RB ( HARD_QUEUESMAX )
on the value to which the
.I queues_max
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.
.SH SEE ALSO
.BR getrlimit (2),
.BR mq_getsetattr (2),