On Wed, 21 Mar 2018, Warner Losh wrote:
On Wed, Mar 21, 2018 at 11:53 AM, Bruce Evans <b...@optusnet.com.au> wrote:
On Wed, 21 Mar 2018, Warner Losh wrote:
Log:
Unlock giant when calling shutdown_nice()
This breaks the driver. Giant is syscons' driver lock, and also the
interrupt handler lock for at least the atkbd keyboard driver, so vt
sometimes holds the lock for.
OK. I got carried away. You're right. The proper fix is to unlock Giant at
the top of kern_reboot() instead. This handles the case where we call
shutdown_nice() with no init running and have to call kern_reboot directly.
Otherwise it's perfectly fine to just call shutdown_nice() with Giant held
since we just signal init from there. So I'll revert this change and make
that other change instead.
...
Good point. I think the following change is good for everything except
calling shutdown_nice() from a fast interrupt handler with noinit running:
diff --git a/sys/kern/kern_shutdown.c b/sys/kern/kern_shutdown.c
index e5ea9644ad3f..564aecd811be 100644
--- a/sys/kern/kern_shutdown.c
+++ b/sys/kern/kern_shutdown.c
@@ -366,6 +366,12 @@ kern_reboot(int howto)
{
static int once = 0;
+ /*
+ * Drop Giant once and for all.
+ */
+ while (mtx_owned(&Giant))
+ mtx_unlock(&Giant);
+
#if defined(SMP)
/*
* Bind us to the first CPU so that all shutdown code runs there.
Some
Comments?
Try putting this in vfs_mountroot_parse() and/or the second clause of
shutdown_nice() only. The only other calls are from is from sys_reboot()
and vpanic(). sys_reboot() is either MPSAFE or not, and it should know
when it is safe to drop its Giant lock if at all. vpanic() sets
SCHEDULER_STOPPED() to avoid seeing problems with Giant or any other
mutex.
Bruce
_______________________________________________
svn-src-head@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-head
To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
