Bug 170874
| Summary: | Unable to create posix message queue of length > 10 | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Daniel Shay <dshay> |
| Component: | kernel | Assignee: | Kernel Maintainer List <kernel-maint> |
| Status: | CLOSED NOTABUG | QA Contact: | Brian Brock <bbrock> |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 4 | CC: | wtogami |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | powerpc | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2005-10-15 12:58:42 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
This doesn't have much with glibc, for mq_open glibc acts just as a wrapper
around kernel syscall. Strace shows:
mq_open("mq_open_name_5910", O_RDWR|O_CREAT, 0600, {mq_maxmsg=100, mq_msgsize=4})
= -1 EINVAL (Invalid argument)
The kernel has several limits on how big a message queue can be to avoid
users grabbing too much kernel memory.
Root (well, CAP_SYS_RESOURCE holder) is allowed to create bigger queues than
normal users, and some of the limits are tweakable through sysctl/proc,
some are tweakable through ulimit -q.
See /proc/sys/fs/mqueue/*
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From Bugzilla Helper: User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.12) Gecko/20050915 Firefox/1.0.7 Description of problem: I am unable to create posix message queues with a mq_maxmsg > 10. The default mq_open will open a queue of 10 messages of 8192 bytes. Queue lengths of 100 worked on previous versions of glibc. {{{ #include <stdio.h> #include <mqueue.h> #include <fcntl.h> #include <sys/stat.h> #include <sys/types.h> #include <unistd.h> #include <string.h> #include <sys/wait.h> #include <errno.h> #define NAMESIZE 50 #define QUEUESIZE 100 int main () { mqd_t myMq; struct mq_attr attr; struct mq_attr getattr; char qname[NAMESIZE]; sprintf(qname, "/mq_open_name_%d", getpid()); attr.mq_msgsize = 4; attr.mq_maxmsg = QUEUESIZE; myMq = mq_open(qname, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR, &attr); if (myMq == -1) { printf("errno=%d description=%s\n", errno, strerror(errno)); } else { printf("Opened queue\n"); mq_getattr(myMq, &getattr); printf(Message Size=%ld Queue Length=%ld\n", getattr.mq_msgsize, mq_mq_maxmsg ); mq_close(myMq); mq_unlink(qname); } return 0; } }}} Compile Command: g++ -o mqueue mqueue.cpp -lrt Version-Release number of selected component (if applicable): glibc-2.3.5-10.3 How reproducible: Always Steps to Reproduce: 1. Compile the given program with a QUEUESIZE > 10 2. Review output. Actual Results: errno=22 description=Invalid argument Expected Results: Opened queue Message Size=4 Queue Length=QUEUESIZE Additional info: I have run this code on a ppc64 and i386. Kernel Version 2.6.13-1.1526_FC4 and 2.6.11.1.1369_FC4 respectively with identical results.