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Improve kqueue() support in the LinuxKPI. Some applications using the

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kqueue() does not set non-blocking I/O mode for event driven read of
file descriptors. This means the LinuxKPI internal kqueue read and
write event flags must be updated before the next read and/or write
system call. Else the read and/or write system call may block. This
can happen when there is no more data to read following a previous
read event. Then the application also gets blocked from processing
other events. This situation can also be solved by the applications
setting and using non-blocking I/O mode.

MFC after:		1 week
Sponsored by:		Mellanox Technologies
This commit is contained in:
Hans Petter Selasky 2017-06-02 16:52:18 +00:00
parent 639af71ab1
commit 67e984c8f2
1 changed files with 26 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
sys/compat/linuxkpi/common/src/linux_compat.c
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@ -438,7 +438,7 @@ linux_kq_lock_unowned(void *arg)
}
static void
linux_dev_kqfilter_poll(struct linux_file *);
linux_dev_kqfilter_poll(struct linux_file *, int);
struct linux_file *
linux_file_alloc(void)
@ -856,9 +856,11 @@ linux_dev_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag,
current->bsd_ioctl_len = 0;
}
if (error == EWOULDBLOCK)
linux_dev_kqfilter_poll(filp);
else if (error == ERESTARTSYS)
if (error == EWOULDBLOCK) {
/* update kqfilter status, if any */
linux_dev_kqfilter_poll(filp,
LINUX_KQ_FLAG_HAS_READ | LINUX_KQ_FLAG_HAS_WRITE);
} else if (error == ERESTARTSYS)
error = ERESTART;
return (error);
}
@ -893,14 +895,15 @@ linux_dev_read(struct cdev *dev, struct uio *uio, int ioflag)
uio->uio_resid -= bytes;
} else {
error = -bytes;
if (error == EWOULDBLOCK)
linux_dev_kqfilter_poll(filp);
else if (error == ERESTARTSYS)
if (error == ERESTARTSYS)
error = ERESTART;
}
} else
error = ENXIO;
/* update kqfilter status, if any */
linux_dev_kqfilter_poll(filp, LINUX_KQ_FLAG_HAS_READ);
return (error);
}
@ -934,14 +937,15 @@ linux_dev_write(struct cdev *dev, struct uio *uio, int ioflag)
uio->uio_resid -= bytes;
} else {
error = -bytes;
if (error == EWOULDBLOCK)
linux_dev_kqfilter_poll(filp);
else if (error == ERESTARTSYS)
if (error == ERESTARTSYS)
error = ERESTART;
}
} else
error = ENXIO;
/* update kqfilter status, if any */
linux_dev_kqfilter_poll(filp, LINUX_KQ_FLAG_HAS_WRITE);
return (error);
}
@ -1032,21 +1036,20 @@ static struct filterops linux_dev_kqfiltops_write = {
};
static void
linux_dev_kqfilter_poll(struct linux_file *filp)
linux_dev_kqfilter_poll(struct linux_file *filp, int kqflags)
{
int temp;
spin_lock(&filp->f_kqlock);
temp = (filp->f_kqflags & (LINUX_KQ_FLAG_HAS_READ | LINUX_KQ_FLAG_HAS_WRITE));
filp->f_kqflags &= ~(LINUX_KQ_FLAG_NEED_READ | LINUX_KQ_FLAG_NEED_WRITE);
spin_unlock(&filp->f_kqlock);
if (temp != 0) {
if (filp->f_kqflags & kqflags) {
/* get the latest polling state */
temp = filp->f_op->poll(filp, NULL);
spin_lock(&filp->f_kqlock);
/* clear kqflags */
filp->f_kqflags &= ~(LINUX_KQ_FLAG_NEED_READ |
LINUX_KQ_FLAG_NEED_WRITE);
/* update kqflags */
if (temp & (POLLIN | POLLOUT)) {
spin_lock(&filp->f_kqlock);
if (temp & POLLIN)
filp->f_kqflags |= LINUX_KQ_FLAG_NEED_READ;
if (temp & POLLOUT)
@ -1054,8 +1057,8 @@ linux_dev_kqfilter_poll(struct linux_file *filp)
/* make sure the "knote" gets woken up */
KNOTE_LOCKED(&filp->f_selinfo.si_note, 0);
spin_unlock(&filp->f_kqlock);
}
spin_unlock(&filp->f_kqlock);
}
}
@ -1099,7 +1102,10 @@ linux_dev_kqfilter(struct cdev *dev, struct knote *kn)
if (error == 0) {
linux_set_current(td);
linux_dev_kqfilter_poll(filp);
/* update kqfilter status, if any */
linux_dev_kqfilter_poll(filp,
LINUX_KQ_FLAG_HAS_READ | LINUX_KQ_FLAG_HAS_WRITE);
}
return (error);
}