Bug 218320
| Summary: | splice with SPLICE_F_NONBLOCK returns -1 EAGAIN on writeable pipes | ||||||
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| Product: | [Fedora] Fedora | Reporter: | James Antill <james.antill> | ||||
| Component: | kernel | Assignee: | Kernel Maintainer List <kernel-maint> | ||||
| Status: | CLOSED INSUFFICIENT_DATA | QA Contact: | Brian Brock <bbrock> | ||||
| Severity: | medium | Docs Contact: | |||||
| Priority: | medium | ||||||
| Version: | 6 | CC: | jonstanley, wtogami | ||||
| Target Milestone: | --- | ||||||
| Target Release: | --- | ||||||
| Hardware: | All | ||||||
| OS: | Linux | ||||||
| Whiteboard: | |||||||
| Fixed In Version: | Doc Type: | Bug Fix | |||||
| Doc Text: | Story Points: | --- | |||||
| Clone Of: | Environment: | ||||||
| Last Closed: | 2008-02-08 04:28:59 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: | |||||||
| Bug Depends On: | |||||||
| Bug Blocks: | 427887 | ||||||
| Attachments: |
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Created attachment 142752 [details]
Test splice call and flags.
(This is a mass-update to all current FC6 kernel bugs in NEW state) Hello, I'm reviewing this bug list as part of the kernel bug triage project, an attempt to isolate current bugs in the Fedora kernel. http://fedoraproject.org/wiki/KernelBugTriage I am CC'ing myself to this bug, however this version of Fedora is no longer maintained. Please attempt to reproduce this bug with a current version of Fedora (presently Fedora 8). If the bug no longer exists, please close the bug or I'll do so in a few days if there is no further information lodged. Thanks for using Fedora! Per the previous comment in this bug, I am closing it as INSUFFICIENT_DATA, since no information has been lodged for over 30 days. Please re-open this bug or file a new one if you can provide the requested data, and thanks for filing the original report! |
Description of problem: Although there is no documentation on splice() I assume that SPLICE_F_NONBLOCK is supposed to be the same as having a nonblocking flag on the pipe ... this isn't so, with the SPLICE_F_NONBLOCK flag splice() can return -1 EAGAIN when poll() says the pipe is ready to accept data. strace: poll([{fd=4, events=POLLOUT, revents=POLLOUT}, {fd=6, events=POLLOUT, revents=POLLOUT}], 2, -1) = 2 SYS_313(0x7, 0, 0x4, 0, 0x3d060000) = -1 EAGAIN (Resource temporarily unavailable) SYS_313(0x9, 0, 0x6, 0, 0x618e000) = -1 EAGAIN (Resource temporarily unavailable) ...I've included a test program. Note that even if I'm wrong in my assumption of what SPLICE_F_NONBLOCK does, the only other thing I could imagine is that it is doing a real nonblock on the page cache too ... and I've included readahead() calls which should "fix" that (although not having a working poll() would make that definition much less useful). Version-Release number of selected component (if applicable): % uname -a ~/glibc-tst-rpms Linux code.and.org 2.6.18-1.2849.fc6 #1 SMP Fri Nov 10 12:45:28 EST 2006 i686 athlon i386 GNU/Linux ...note that although the syscall is in glibc FC6, it's broken (fixed in rawhide) if you have a rawhide/test glibc and want to make sure it's not that just change the LOCAL_SPLICE define -- I've done this in my testing. How reproducible: Always Additional info: See the attached splice test application. Note that if you change USE_O_NONBLOCK_R from 0 to 1 and USE_SPLICE_NONBLOCK_R from 1 to 0, the test program will use fcntl() O_NONBLOCK instead of the SPLICE_F_NONBLOCK flag which does the exected thing. Use it like: ./splicetst /tmp/big_1GB /tmp/o1 /tmp/big_100MB /tmp/o2