Messages in this thread |  | | Date | Mon, 19 May 2003 19:54:41 -0400 | From | Pete Zaitcev <> | Subject | Re: recursive spinlocks. Shoot. |
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>> Let's quote the example from rubini & corbet of the sbull block device >> driver. The request function ends like so: > > defective locking in a driver is no excuse to pamper over it with > recusrive shite.
Arjan is a little too harsh here, but on the principle I happen to agree, because I worked with systems which allow recursive locks. They very often cover up for programmer's lack of basic understanding. Worse, sometimes even experienced programmers can do poorly. I ran into the latter cathegory of code when fixing so-called "presto" in Solaris (now replaced by Encore-originated code).
Normal spinlocks are not without problems, in particular people tend to write:
void urb_rm_priv_locked(struct urb *) { ...... } void urb_rm_priv(struct urb *u) { spin_lock_irqsave(); urb_rm_prin_locked(u); spin_unlock_irqrestore(); }
Which eats a stack frame. We make this tradeoff on purpose, as a lesser evil.
BTW, I do not see Linus and his leutenants rebuking the onslaught of recursive ingenuity in this thread. Ignoring the hogwash, or waiting and watching?
-- Pete - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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