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, 11 May 2009 18:43:27 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	David Miller <davem@...emloft.net>
CC:	linuxppc-dev@...abs.org, paulus@...ba.org, netdev@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: question about softirqs


This started out as a thread on the ppc list, but on the suggestion of
DaveM and Paul Mackerras I'm expanding the receiver list a bit.

Currently, if a softirq is raised in process context the
TIF_RESCHED_PENDING flag gets set and on return to userspace we run the
scheduler, expecting it to switch to ksoftirqd to handle the softirqd
processing.

I think I see a possible problem with this. Suppose I have a SCHED_FIFO
task spinning on recvmsg() with MSG_DONTWAIT set. Under the scenario
above, schedule() would re-run the spinning task rather than ksoftirqd,
thus preventing any incoming packets from being sent up the stack until
we get a real hardware interrupt--which could be a whole jiffy if
interrupt mitigation is enabled in the net device.

DaveM pointed out that if we're doing transmits we're likely to hit
local_bh_enable(), which would process the softirq work.  However, I
think we may still have a problem in the above rx-only scenario--or is
it too contrived to matter?

Thanks,

Chris
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists