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Open Source and information security mailing list archives
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Date: Fri, 7 Dec 2012 22:17:09 +0000 From: "Luck, Tony" <tony.luck@...el.com> To: Seiji Aguchi <seiji.aguchi@....com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> CC: "cbouatmailru@...il.com" <cbouatmailru@...il.com>, "ccross@...roid.com" <ccross@...roid.com>, "keescook@...omium.org" <keescook@...omium.org>, "dzickus@...hat.com" <dzickus@...hat.com>, "dle-develop@...ts.sourceforge.net" <dle-develop@...ts.sourceforge.net>, Satoru Moriya <satoru.moriya@....com> Subject: RE: [RFC][PATCH] pstore: Skip spinlock when just one cpu is online > This patch skips taking a psinfo->buf_lock when just one cpu is online > because stopped cpus turn to offline via smp_send_stop() > in some architectures like x86, powerpc or arm64. That seems an impressive list of preconditions. So for this to help we need to have taken all but one cpu offline, then be in some code that is holding the pstore lock and get hit by an NMI which causes us to recurse into the pstore code. Can all these things really happen (did you run into this problem on a real system?). Or is this just a theoretical problem. Ugly (but practical) hacks might be OK to solve real problems. But do we really want them to fix problems that actually never happen? -Tony -- 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/
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