On Thu, May 21, 2009 at 07:05:17PM +0200, Attilio Rao wrote:
> 2009/5/21 Kostik Belousov <kostik...@gmail.com>:
> > On Thu, May 21, 2009 at 09:23:15AM -0700, Scott Long wrote:
> >> Kostik Belousov wrote:
> >> >We do have the KPI for the callers that cannot drop the locks and need
> >> >to do destroy_dev, destroy_dev_sched(9).
> >>
> >> Good to know, I'll look at destroy_dev_sched(). I'd rather not have to
> >> roll my own decoupled version. And I understand the argument about
> >> destroy_dev being a drain point for the API. However, what about
> >> create_dev()? Making that non-blocking would help a lot.
> >
> > create_dev() can be made non-blocking, and this is the first argument pro
> > Attilio patch.
> >
> > From the quick look, all that is needed is to replace M_WAITOK with
> > M_NOWAIT inside prep_cdevsw() and devfs_alloc(). Untested patch below.
> >
> > diff --git a/sys/fs/devfs/devfs_devs.c b/sys/fs/devfs/devfs_devs.c
> > index 4041911..f470ee8 100644
> > --- a/sys/fs/devfs/devfs_devs.c
> > +++ b/sys/fs/devfs/devfs_devs.c
> > @@ -120,7 +120,7 @@ devfs_alloc(void)
> > struct cdev *cdev;
> > struct timespec ts;
> >
> > - cdp = malloc(sizeof *cdp, M_CDEVP, M_USE_RESERVE | M_ZERO |
> > M_WAITOK);
> > + cdp = malloc(sizeof *cdp, M_CDEVP, M_USE_RESERVE | M_ZERO |
> > M_NOWAIT);
> >
> > cdp->cdp_dirents = &cdp->cdp_dirent0;
> > cdp->cdp_dirent0 = NULL;
> > diff --git a/sys/kern/kern_conf.c b/sys/kern/kern_conf.c
> > index 284f482..acdd44a 100644
> > --- a/sys/kern/kern_conf.c
> > +++ b/sys/kern/kern_conf.c
> > @@ -559,7 +559,7 @@ prep_cdevsw(struct cdevsw *devsw)
> > return;
> > if (devsw->d_flags & D_NEEDGIANT) {
> > dev_unlock();
> > - dsw2 = malloc(sizeof *dsw2, M_DEVT, M_WAITOK);
> > + dsw2 = malloc(sizeof *dsw2, M_DEVT, M_NOWAIT);
> > dev_lock();
> > } else
> > dsw2 = NULL;
>
> You need to check return values here if it returns NULL.
>
> IMHO, having a non-sleepable version of destroy_dev(), create_dev()
> and such would be ideal.
> Ideally, we should resolve all the sleeping point and do the conversion.
> I'm unable to check the code right now.
Sure. Something like this.
diff --git a/share/man/man9/make_dev.9 b/share/man/man9/make_dev.9
index b39ca8b..0844e64 100644
--- a/share/man/man9/make_dev.9
+++ b/share/man/man9/make_dev.9
@@ -133,6 +133,7 @@ The following values are currently accepted:
.Pp
.Bd -literal -offset indent -compact
MAKEDEV_REF reference the created device
+MAKEDEV_NOWAIT do not sleep, may return NULL
.Ed
.Pp
The
diff --git a/sys/fs/devfs/devfs_devs.c b/sys/fs/devfs/devfs_devs.c
index 4041911..79f7893 100644
--- a/sys/fs/devfs/devfs_devs.c
+++ b/sys/fs/devfs/devfs_devs.c
@@ -114,17 +114,21 @@ SYSCTL_INT(_debug_sizeof, OID_AUTO, cdev_priv, CTLFLAG_RD,
0, sizeof(struct cdev_priv), "sizeof(struct cdev_priv)");
struct cdev *
-devfs_alloc(void)
+devfs_alloc(int flags)
{
struct cdev_priv *cdp;
struct cdev *cdev;
struct timespec ts;
- cdp = malloc(sizeof *cdp, M_CDEVP, M_USE_RESERVE | M_ZERO | M_WAITOK);
+ cdp = malloc(sizeof *cdp, M_CDEVP, M_USE_RESERVE | M_ZERO |
+ ((flags & MAKEDEV_NOWAIT) ? M_NOWAIT : M_WAITOK));
+ if (cdp == NULL)
+ return (NULL);
cdp->cdp_dirents = &cdp->cdp_dirent0;
cdp->cdp_dirent0 = NULL;
cdp->cdp_maxdirent = 0;
+ cdp->cdp_inode = 0;
cdev = &cdp->cdp_c;
@@ -132,6 +136,7 @@ devfs_alloc(void)
LIST_INIT(&cdev->si_children);
vfs_timestamp(&ts);
cdev->si_atime = cdev->si_mtime = cdev->si_ctime = ts;
+ cdev->si_cred = NULL;
return (cdev);
}
diff --git a/sys/fs/devfs/devfs_int.h b/sys/fs/devfs/devfs_int.h
index 5a61dd4..f5612e1 100644
--- a/sys/fs/devfs/devfs_int.h
+++ b/sys/fs/devfs/devfs_int.h
@@ -70,7 +70,7 @@ struct cdev_priv {
#define cdev2priv(c) member2struct(cdev_priv, cdp_c, c)
-struct cdev *devfs_alloc(void);
+struct cdev *devfs_alloc(int);
void devfs_free(struct cdev *);
void devfs_create(struct cdev *dev);
void devfs_destroy(struct cdev *dev);
diff --git a/sys/kern/kern_conf.c b/sys/kern/kern_conf.c
index 284f482..082f5d3 100644
--- a/sys/kern/kern_conf.c
+++ b/sys/kern/kern_conf.c
@@ -482,7 +482,7 @@ giant_mmap(struct cdev *dev, vm_offset_t offset, vm_paddr_t
*paddr, int nprot)
static void
-notify(struct cdev *dev, const char *ev)
+notify(struct cdev *dev, const char *ev, int flags)
{
static const char prefix[] = "cdev=";
char *data;
@@ -491,7 +491,8 @@ notify(struct cdev *dev, const char *ev)
if (cold)
return;
namelen = strlen(dev->si_name);
- data = malloc(namelen + sizeof(prefix), M_TEMP, M_NOWAIT);
+ data = malloc(namelen + sizeof(prefix), M_TEMP,
+ (flags & MAKEDEV_NOWAIT) ? M_NOWAIT : M_WAITOK);
if (data == NULL)
return;
memcpy(data, prefix, sizeof(prefix) - 1);
@@ -501,17 +502,17 @@ notify(struct cdev *dev, const char *ev)
}
static void
-notify_create(struct cdev *dev)
+notify_create(struct cdev *dev, int flags)
{
- notify(dev, "CREATE");
+ notify(dev, "CREATE", flags);
}
static void
notify_destroy(struct cdev *dev)
{
- notify(dev, "DESTROY");
+ notify(dev, "DESTROY", 0);
}
static struct cdev *
@@ -549,24 +550,27 @@ fini_cdevsw(struct cdevsw *devsw)
devsw->d_flags &= ~D_INIT;
}
-static void
-prep_cdevsw(struct cdevsw *devsw)
+static int
+prep_cdevsw(struct cdevsw *devsw, int flags)
{
struct cdevsw *dsw2;
mtx_assert(&devmtx, MA_OWNED);
if (devsw->d_flags & D_INIT)
- return;
+ return (1);
if (devsw->d_flags & D_NEEDGIANT) {
dev_unlock();
- dsw2 = malloc(sizeof *dsw2, M_DEVT, M_WAITOK);
+ dsw2 = malloc(sizeof *dsw2, M_DEVT,
+ (flags & MAKEDEV_NOWAIT) ? M_NOWAIT : M_WAITOK);
dev_lock();
+ if (dsw2 == NULL && !(devsw->d_flags & D_INIT))
+ return (0);
} else
dsw2 = NULL;
if (devsw->d_flags & D_INIT) {
if (dsw2 != NULL)
cdevsw_free_devlocked(dsw2);
- return;
+ return (1);
}
if (devsw->d_version != D_VERSION_01) {
@@ -622,6 +626,7 @@ prep_cdevsw(struct cdevsw *devsw)
if (dsw2 != NULL)
cdevsw_free_devlocked(dsw2);
+ return (1);
}
struct cdev *
@@ -632,9 +637,15 @@ make_dev_credv(int flags, struct cdevsw *devsw, int unit,
struct cdev *dev;
int i;
- dev = devfs_alloc();
+ dev = devfs_alloc(flags);
+ if (dev == NULL)
+ return (NULL);
dev_lock();
- prep_cdevsw(devsw);
+ if (!prep_cdevsw(devsw, flags)) {
+ dev_unlock();
+ devfs_free(dev);
+ return (NULL);
+ }
dev = newdev(devsw, unit, dev);
if (flags & MAKEDEV_REF)
dev_refl(dev);
@@ -661,8 +672,6 @@ make_dev_credv(int flags, struct cdevsw *devsw, int unit,
dev->si_flags |= SI_NAMED;
if (cr != NULL)
dev->si_cred = crhold(cr);
- else
- dev->si_cred = NULL;
dev->si_uid = uid;
dev->si_gid = gid;
dev->si_mode = mode;
@@ -671,7 +680,7 @@ make_dev_credv(int flags, struct cdevsw *devsw, int unit,
clean_unrhdrl(devfs_inos);
dev_unlock_and_free();
- notify_create(dev);
+ notify_create(dev, flags);
return (dev);
}
@@ -746,7 +755,7 @@ make_dev_alias(struct cdev *pdev, const char *fmt, ...)
int i;
KASSERT(pdev != NULL, ("NULL pdev"));
- dev = devfs_alloc();
+ dev = devfs_alloc(0);
dev_lock();
dev->si_flags |= SI_ALIAS;
dev->si_flags |= SI_NAMED;
@@ -763,7 +772,7 @@ make_dev_alias(struct cdev *pdev, const char *fmt, ...)
clean_unrhdrl(devfs_inos);
dev_unlock();
- notify_create(dev);
+ notify_create(dev, 0);
return (dev);
}
@@ -947,9 +956,9 @@ clone_create(struct clonedevs **cdp, struct cdevsw *csw,
int *up, struct cdev **
* the end of the list.
*/
unit = *up;
- ndev = devfs_alloc();
+ ndev = devfs_alloc(0);
dev_lock();
- prep_cdevsw(csw);
+ prep_cdevsw(csw, 0);
low = extra;
de = dl = NULL;
cd = *cdp;
diff --git a/sys/sys/conf.h b/sys/sys/conf.h
index 05c4bb5..7b65862 100644
--- a/sys/sys/conf.h
+++ b/sys/sys/conf.h
@@ -263,6 +263,7 @@ struct cdev *make_dev_cred(struct cdevsw *_devsw, int _unit,
const char *_fmt, ...) __printflike(7, 8);
#define MAKEDEV_REF 0x1
#define MAKEDEV_WHTOUT 0x2
+#define MAKEDEV_NOWAIT 0x4
struct cdev *make_dev_credf(int _flags,
struct cdevsw *_devsw, int _unit,
struct ucred *_cr, uid_t _uid, gid_t _gid, int _mode,
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