From: Cliff Wickman Date: Fri, 22 Jun 2012 13:14:59 +0000 (-0500) Subject: x86/uv: Work around UV2 BAU hangs X-Git-Tag: v3.6-rc1~160^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8b6e511e51f7e540c8e71022318ee4cc9a4567a7;p=pandora-kernel.git x86/uv: Work around UV2 BAU hangs On SGI's UV2 the BAU (Broadcast Assist Unit) driver can hang under a heavy load. To cure this: - Disable the UV2 extended status mode (see UV2_EXT_SHFT), as this mode changes BAU behavior in more ways then just delivering an extra bit of status. Revert status to just two meaningful bits, like UV1. - Use no IPI-style resets on UV2. Just give up the request for whatever the reason it failed and let it be accomplished with the legacy IPI method. - Use no alternate sending descriptor (the former UV2 workaround bcp->using_desc and handle_uv2_busy() stuff). Just disable the use of the BAU for a period of time in favor of the legacy IPI method when the h/w bug leaves a descriptor busy. -- new tunable: giveup_limit determines the threshold at which a hub is so plugged that it should do all requests with the legacy IPI method for a period of time -- generalize disable_for_congestion() (renamed disable_for_period()) for use whenever a hub should avoid using the BAU for a period of time Also: - Fix find_another_by_swack(), which is part of the UV2 bug workaround - Correct and clarify the statistics (new stats s_overipilimit, s_giveuplimit, s_enters, s_ipifordisabled, s_plugged, s_congested) Signed-off-by: Cliff Wickman Link: http://lkml.kernel.org/r/20120622131459.GC31884@sgi.com Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed