A subtle bug sneaked into iSeries recently. On this platform, we
must not normally clear MSR:EE unless it's 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 a few exception entry/exit code path. 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 period 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 spurrious 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 <[EMAIL PROTECTED]>
--
arch/powerpc/kernel/head_64.S | 13 +++++++------
arch/powerpc/kernel/irq.c | 1 -
2 files changed, 7 insertions(+), 7 deletions(-)
--- linux-work.orig/arch/powerpc/kernel/head_64.S 2008-04-02
15:47:20.000000000 +1100
+++ linux-work/arch/powerpc/kernel/head_64.S 2008-04-02 15:48:50.000000000
+1100
@@ -1387,12 +1387,14 @@ __secondary_start:
#ifdef CONFIG_PPC_ISERIES
BEGIN_FW_FTR_SECTION
ori r4,r4,MSR_EE
+ li r8,1
+ stb r8,PACAHARDIRQEN(r13)
END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
#endif
BEGIN_FW_FTR_SECTION
- stb r7,PACASOFTIRQEN(r13)
stb r7,PACAHARDIRQEN(r13)
END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
+ stb r7,PACASOFTIRQEN(r13)
mtspr SPRN_SRR0,r3
mtspr SPRN_SRR1,r4
@@ -1520,15 +1522,14 @@ _INIT_GLOBAL(start_here_common)
#ifdef CONFIG_PPC_ISERIES
BEGIN_FW_FTR_SECTION
mfmsr r5
- ori r5,r5,MSR_EE /* Hard Enabled */
+ ori r5,r5,MSR_EE /* Hard Enabled on iSeries*/
mtmsrd r5
+ li r5,1
END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
#endif
-BEGIN_FW_FTR_SECTION
- stb r5,PACAHARDIRQEN(r13)
-END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
+ stb r5,PACAHARDIRQEN(r13) /* Hard Disabled on others */
- bl .start_kernel
+ bl .start_kernel
/* Not reached */
BUG_OPCODE
Index: linux-work/arch/powerpc/kernel/irq.c
===================================================================
--- linux-work.orig/arch/powerpc/kernel/irq.c 2008-04-02 15:46:34.000000000
+1100
+++ linux-work/arch/powerpc/kernel/irq.c 2008-04-02 15:46:37.000000000
+1100
@@ -143,7 +143,6 @@ void local_irq_restore(unsigned long en)
*/
if (local_paca->lppaca_ptr->int_dword.any_int)
iseries_handle_interrupts();
- return;
}
/*
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