[systemd-bugs] [Bug 83024] New: sd_readahead retries closing an fd on EINTR

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=83024

          Priority: medium
            Bug ID: 83024
          Assignee: systemd-bugs at lists.freedesktop.org
           Summary: sd_readahead retries closing an fd on EINTR
        QA Contact: systemd-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: All
          Reporter: sstewartgallus00 at mylangara.bc.ca
          Hardware: Other
            Status: NEW
           Version: unspecified
         Component: general
           Product: systemd

The code in the touch function of sd-readahead.c:

        for (;;) {
                if (close(fd) >= 0)
                        break;

                if (errno != EINTR)
                        return -errno;
        }

The ultra-paranoid ultra portable correct code:

    /*
     * The state of a file descriptor after close gives an EINTR error
     * is unspecified by POSIX so this function avoids the problem by
     * simply blocking all signals.
     */
    int errnum;
    sigset_t sigset;

    /* First use the signal set for the full set */
    sigfillset(&sigset);

    pthread_sigmask(SIG_BLOCK, &sigset, &sigset);

    /* Then reuse the signal set for the old set */

    if (-1 == close(fd)) {
        errnum = errno;
        assert(errnum != 0);
    } else {
        errnum = 0;
    }

    pthread_sigmask(SIG_SETMASK, &sigset, NULL);

    return errnum;

The system specific but mostly standard code you probably want:

    int errnum;
    if (-1 == close(fd)) {
        errnum = errno;
        assert(errnum != 0);
        /* On Linux and probably most platforms EINTR can't happen or
         * would close the file succesfully anyways. */
        if (EINTR == errnum) {
            errnum = 0;
        }
    } else {
        errnum = 0;
    }
    return errnum;

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