android_kernel_xiaomi_sm8350/arch/m32r
Hirokazu Takata cf535ea52e [PATCH] m32r: update sys_tas() routine
This patch updates and fixes sys_tas() routine for m32r.

In the previous implementation, a lockup rarely caused at sys_tas()
routine in SMP environment.

> > The problem is that touching *addr will generate an oops if that page isn't
> > paged in.  If we convert it to use get_user() then that's an improvement,
> > but we must not run get_user() under spinlock or local_irq_disable().

I rewrote sys_tas() routine by using "lock -> unlock" instructions, and
utilizing the m32r's interrupt handling characteristics; the m32r processor
can accept interrupts only at the 32-bit instruction boundary.  So, the
"unlock" instruction can be executed continuously after the "lock"
instruction execution without any interruptions.

In addition, to solve such a page_fault problem, I use a fixup code like
get_user().

And, as for the kernel lockup problem, we found that a calling
do_page_fault() routine with disabling interrupts might cause a lockup at
flush_tlb_others(), because we checked a completion of IPI handler's
operations in a spin-locked critical section.

Therefore, by using "lock -> unlock" code, we can implement the sys_tas()
rouitine without disabling interrupts explicitly, then no lockups would
happen at flush_tlb_others(), I hope.

Compile check and some working test in SMP environment have done.

Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-20 20:00:12 -08:00
..
boot [PATCH] m32r: Fix M32104 cache flushing routines 2006-01-06 08:33:44 -08:00
kernel [PATCH] m32r: update sys_tas() routine 2006-02-20 20:00:12 -08:00
lib [PATCH] fix missing includes 2005-10-30 17:37:32 -08:00
m32104ut [PATCH] m32r: Support M32104UT target platform 2006-01-06 08:33:43 -08:00
m32700ut [PATCH] m32r: Update defconfig files 2005-06-21 19:07:31 -07:00
mappi [PATCH] m32r: Update defconfig files 2005-06-21 19:07:31 -07:00
mappi2 [PATCH] m32r: Update defconfig files 2005-06-21 19:07:31 -07:00
mappi3 [PATCH] m32r: Support M3A-2170(Mappi-III) platform 2005-06-21 19:07:30 -07:00
mm [PATCH] m32r: Fix M32104 cache flushing routines 2006-01-06 08:33:44 -08:00
oaks32r [PATCH] m32r: Update defconfig files 2005-06-21 19:07:31 -07:00
oprofile Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
opsput [PATCH] m32r: Update defconfig files 2005-06-21 19:07:31 -07:00
defconfig [PATCH] m32r: Update defconfig files 2005-06-21 19:07:31 -07:00
Kconfig [PATCH] "tiny-make-id16-support-optional" fixes 2006-01-10 08:01:23 -08:00
Kconfig.debug [PATCH] Kconfig fix (DEBUG_PAGEALLOC on m32r) 2005-08-23 18:43:41 -07:00
Makefile [PATCH] m32r: set CHECKFLAGS properly 2005-09-26 18:29:50 -07:00