MIPS: Make irqflags.h functions preempt-safe for non-mipsr2 cpus
For non MIPSr2 processors, such as the BMIPS 5000, calls to
arch_local_irq_disable() and others may be preempted, and in doing
so a stale value may be restored to c0_status. This fix disables
preemption for such processors prior to the call and enables it
after the call.
Those functions that needed this fix have been "outlined" to
mips-atomic.c, as they are no longer good candidates for inlining.
This bug was observed in a BMIPS 5000, occuring once every few hours
in a continuous reboot test. It was traced to the write_lock_irq()
function which was being invoked in release_task() in exit.c.
By placing a number of "nops" inbetween the mfc0/mtc0 pair in
arch_local_irq_disable(), which is called by write_lock_irq(), we
were able to greatly increase the occurance of this bug. Similarly,
the application of this commit silenced the bug.
Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: David Daney <ddaney.cavm@gmail.com>
Cc: Kevin Cernekee cernekee@gmail.com
Cc: Jim Quinlan <jim2101024@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/4321/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/lib/Makefile b/arch/mips/lib/Makefile
index a7b89371..eeddc58 100644
--- a/arch/mips/lib/Makefile
+++ b/arch/mips/lib/Makefile
@@ -3,7 +3,8 @@
#
lib-y += bitops.o csum_partial.o delay.o memcpy.o memset.o \
- strlen_user.o strncpy_user.o strnlen_user.o uncached.o
+ mips-atomic.o strlen_user.o strncpy_user.o \
+ strnlen_user.o uncached.o
obj-y += iomap.o
obj-$(CONFIG_PCI) += iomap-pci.o
