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MIPS: Build uasm-generated code only once to avoid CPU Hotplug problem

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This and the next patch resolve memory corruption problems while CPU
hotplug. Without these patches, memory corruption can triggered easily
as below:

On a quad-core MIPS platform, use "spawn" of UnixBench-5.1.3 (http://
code.google.com/p/byte-unixbench/) and a CPU hotplug script like this
(hotplug.sh):
while true; do
echo 0 >/sys/devices/system/cpu/cpu1/online
echo 0 >/sys/devices/system/cpu/cpu2/online
echo 0 >/sys/devices/system/cpu/cpu3/online
sleep 1
echo 1 >/sys/devices/system/cpu/cpu1/online
echo 1 >/sys/devices/system/cpu/cpu2/online
echo 1 >/sys/devices/system/cpu/cpu3/online
sleep 1
done

Run "hotplug.sh" and then run "spawn 10000", spawn will get segfault
after a few minutes.

This patch:
Currently, clear_page()/copy_page() are generated by Micro-assembler
dynamically. But they are unavailable until uasm_resolve_relocs() has
finished because jump labels are illegal before that. Since these
functions are shared by every CPU, we only call build_clear_page()/
build_copy_page() only once at boot time. Without this patch, programs
will get random memory corruption (segmentation fault, bus error, etc.)
while CPU Hotplug (e.g. one CPU is using clear_page() while another is
generating it in cpu_cache_init()).

For similar reasons we modify build_tlb_refill_handler()'s invocation.

V2:
1, Rework the code to make CPU#0 can be online/offline.
2, Introduce cpu_has_local_ebase feature since some types of MIPS CPU
   need a per-CPU tlb_refill_handler().

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Hongbing Hu <huhb@lemote.com>
Acked-by: David Daney <david.daney@cavium.com>
Patchwork: http://patchwork.linux-mips.org/patch/4994/
Acked-by: John Crispin <blogic@openwrt.org>
This commit is contained in:
Huacai Chen 2013-03-17 11:49:38 +00:00 committed by Ralf Baechle
parent 59b435d1ad
commit 8759934e2b
4 changed files with 22 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
arch/mips/include/asm/cpu-features.h
View file

@ -113,6 +113,9 @@
#ifndef cpu_has_pindexed_dcache
#define cpu_has_pindexed_dcache (cpu_data[0].dcache.flags & MIPS_CACHE_PINDEX)
#endif
#ifndef cpu_has_local_ebase
#define cpu_has_local_ebase 1
#endif
/*
* I-Cache snoops remote store. This only matters on SMP. Some multiprocessors

1
arch/mips/include/asm/mach-loongson/cpu-feature-overrides.h
View file

@ -57,5 +57,6 @@
#define cpu_has_vint 0
#define cpu_has_vtag_icache 0
#define cpu_has_watch 1
#define cpu_has_local_ebase 0
#endif /* __ASM_MACH_LOONGSON_CPU_FEATURE_OVERRIDES_H */

10
arch/mips/mm/page.c
View file

@ -247,6 +247,11 @@ void __cpuinit build_clear_page(void)
struct uasm_label *l = labels;
struct uasm_reloc *r = relocs;
int i;
static atomic_t run_once = ATOMIC_INIT(0);
if (atomic_xchg(&run_once, 1)) {
return;
}
memset(labels, 0, sizeof(labels));
memset(relocs, 0, sizeof(relocs));
@ -389,6 +394,11 @@ void __cpuinit build_copy_page(void)
struct uasm_label *l = labels;
struct uasm_reloc *r = relocs;
int i;
static atomic_t run_once = ATOMIC_INIT(0);
if (atomic_xchg(&run_once, 1)) {
return;
}
memset(labels, 0, sizeof(labels));
memset(relocs, 0, sizeof(relocs));

10
arch/mips/mm/tlbex.c
View file

@ -2162,8 +2162,11 @@ void __cpuinit build_tlb_refill_handler(void)
case CPU_TX3922:
case CPU_TX3927:
#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
build_r3000_tlb_refill_handler();
if (cpu_has_local_ebase)
build_r3000_tlb_refill_handler();
if (!run_once) {
if (!cpu_has_local_ebase)
build_r3000_tlb_refill_handler();
build_r3000_tlb_load_handler();
build_r3000_tlb_store_handler();
build_r3000_tlb_modify_handler();
@ -2192,9 +2195,12 @@ void __cpuinit build_tlb_refill_handler(void)
build_r4000_tlb_load_handler();
build_r4000_tlb_store_handler();
build_r4000_tlb_modify_handler();
if (!cpu_has_local_ebase)
build_r4000_tlb_refill_handler();
run_once++;
}
build_r4000_tlb_refill_handler();
if (cpu_has_local_ebase)
build_r4000_tlb_refill_handler();
}
}