linux-kernel - Re: [PATCH] MIPS: Enable interrupts in arch_cpu

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]

Date:	Thu, 2 May 2013 09:45:08 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ralf Baechle <ralf@...ux-mips.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jonas Gorski <jogo@...nwrt.org>, eunb.song@...sung.com,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] MIPS: Enable interrupts in arch_cpu_idle()

On Thu, May 2, 2013 at 7:58 AM, Ralf Baechle <ralf@...ux-mips.org> wrote:
>
> For a while we just used to live with the race condition resulting from
> not disabling interrupts in the idle loop.  Then c65a5480 fixed this by
> checking if we're returning to the WAIT instruction in the idle loop
> when returning from an interrupt and iff so, rolling back the
> program counter to point to the if (test_thread_flag(TIF_NEED_RESCHED))
> test at the beginning of rollback_r4k_wait.

Umm. That sounds buggy. What if there was an interrupt *between* the
two places, not right at the wait instruction?

It seriously sounds like MIPS should do this by enabling interrupts in
the *assembly* code immediately preceding the wait instruction. IOW,
you'd effectively have the same kind of "sti; halt" kind of sequence
that x86 has. Not "enable interrupts" + C compiler puts random
instructions here + "wait".

                       Linus
--
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/