Re: svn commit: r192535 - head/sys/kern

[Kostik Belousov]

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;

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