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getrlimit.2: Since Linux 3.5, the accounting formula for RLIMIT_MSGQUEUE has changed 

Reported-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2014-10-01 09:47:42 +02:00
parent 1aa06521e9
commit e15dc33869
1 changed files with 22 additions and 6 deletions
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28
man2/getrlimit.2
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@ -250,8 +250,19 @@ Each message queue that the user creates counts (until it is removed)
against this limit according to the formula:
.nf
bytes = attr.mq_maxmsg * sizeof(struct msg_msg *) +
attr.mq_maxmsg * attr.mq_msgsize
Since Linux 3.5:
bytes = attr.mq_maxmsg * sizeof(struct msg_msg) +
min(attr.mq_maxmsg, MQ_PRIO_MAX) *
sizeof(struct posix_msg_tree_node)+
/* For overhead */
attr.mq_maxmsg * attr.mq_msgsize;
/* For message data */
Linux 3.4 and earlier:
bytes = attr.mq_maxmsg * sizeof(struct msg_msg *) +
/* For overhead */
attr.mq_maxmsg * attr.mq_msgsize;
/* For message data */
.fi
where
@ -259,11 +270,16 @@ where
is the
.I mq_attr
structure specified as the fourth argument to
.BR mq_open (3).
.BR mq_open (3),
and the
.I msg_msg
and
.I posix_msg_tree_node
structures are kernel-internal structures.
The first addend in the formula, which includes
.I "sizeof(struct msg_msg\ *)"
(4 bytes on Linux/i386), ensures that the user cannot
The "overhead" addend in the formula accounts for overhead
bytes required by the implementation
and ensures that the user cannot
create an unlimited number of zero-length messages (such messages
nevertheless each consume some system memory for bookkeeping overhead).
.TP