linux-kernel - Re: [PATCH -v2] use per cpu data for single cpu ipi calls

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

Message-ID: <alpine.DEB.1.10.0901291249000.27527@gandalf.stny.rr.com>
Date:	Thu, 29 Jan 2009 12:50:18 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>, npiggin@...e.de,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...radead.org>,
	jens.axboe@...cle.com
Subject: Re: [PATCH -v2] use per cpu data for single cpu ipi calls


On Thu, 29 Jan 2009, Steven Rostedt wrote:
> 
> > 
> > But to be irq-safe, you now need to protect the _whole_ region against 
> > interrupts, because otherwise an incoming interrupt will hit while the 
> > CSD_FLAG_LOCK bit is set, perhaps _before_ the actual IPI has been sent, 
> > and now nothing will ever clear it. So the interrupt handler that tries to 
> > send an IPI will now spin forever.
> 
> Again, this code is not allowed to run from an interrupt handler.
> 
> > 
> > So NAK on this patch. I think the approach is correct, but the 
> > implementation is buggy.

My whole assumption of this is that smp_call_function_single can not be 
called from an interrupt handler. If it can, then perhaps I just change 
the spinlock to the cmpxchg code, and put a:

	WARN_ON(cpu == smp_processor_id());

-- Steve

--
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/