From: Benjamin Herrenschmidt Date: Wed, 2 Apr 2008 04:58:40 +0000 (+1100) Subject: [POWERPC] Fix iSeries hard irq enabling regression X-Git-Tag: v2.6.25-rc9~76^2~4 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ff3da2e0938bae36d10d69c22bce0177b067a9e2;p=pandora-kernel.git [POWERPC] Fix iSeries hard irq enabling regression A subtle bug sneaked into iSeries recently. On this platform, we must not normally clear MSR:EE (the hardware external interrupt enable) except for short periods of time. Taking an interrupt while soft-disabled doesn't cause us to clear it for example. The iSeries kernel expects to mostly run with MSR:EE enabled at all times except in a few exception entry/exit code paths. Thus local_irq_enable() doesn't check if it needs to hard-enable as it expects this to be unnecessary on iSeries. However, hard_irq_disable() _does_ cause MSR:EE to be cleared, including on iSeries. A call to it was recently added to the context switch code, thus causing interrupts to become disabled for a long periods of time, causing the iSeries watchdog to kick in under some circumstances and other nasty things. This patch fixes it by making local_irq_enable() properly re-enable MSR:EE on iSeries. It basically removes a return statement here to make iSeries use the same code path as everybody else. That does mean that we might occasionally get spurious decrementer interrupts but I don't think that matters. Another option would have been to make hard_irq_disable() a nop on iSeries but I didn't like it much, in case we have good reasons to hard-disable. Part of the patch is fixes to make sure the hard_enabled PACA field is properly set on iSeries as it used not to be before, since it was mostly unused. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Paul Mackerras --- Reading git-diff-tree failed