linux-kernel - Busy-waiting with interrupts disabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 12 Dec 2011 17:12:14 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	USB list <linux-usb@...r.kernel.org>
cc:	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Busy-waiting with interrupts disabled

How long is it okay to busy-wait with interrupts disabled?  Are there 
any clear-cut guidelines?

My feeling is that for ordinary desktop use, 1-2 ms should be about the
limit, but other people may feel differently.  (There's one spot in
ehci-hcd where the delay can last up to 250 ms, which does seem rather
excessive.  Fortunately it never takes that long unless the hardware is
broken.)

No doubt the RT people would say the upper bound should be on the order
of a few microseconds or less.  I'd be happy to change ehci-hcd, which
has several delays in the 1-2 ms range -- but they tend to be nested
inside routines that are called within the scope of spinlock_irq, which
means a fair amount of rewriting would be needed.

Any thoughts or recommendations?

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/