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authorMaksim Rayskiy <maksim.rayskiy@gmail.com>2011-11-10 17:59:45 +0000
committerRalf Baechle <ralf@linux-mips.org>2011-11-10 17:59:45 +0000
commit5c200197130e307de6eba72fc335c83c9dd6a5bc (patch)
treef633ada1e41c893822f4075dcfea0ae2d36deb0a
parentb2f909419b72cf043814bf17b96c93d4695378a1 (diff)
downloadlinux-5c200197130e307de6eba72fc335c83c9dd6a5bc.tar.bz2
MIPS: ASID conflict after CPU hotplug
I am running SMP Linux 2.6.37-rc1 on BMIPS5000 (single core dual thread) and observe some abnormalities when doing system suspend/resume which I narrowed down to cpu hotplugging. The suspend brings the second thread processor down and then restarts it, after which I see memory corruption in userspace. I started digging and found out that problem occurs because while doing execve() the child process is getting the same ASID as the parent, which obviously corrupts parent's address space. Further digging showed that activate_mm() calls get_new_mmu_context() to get a new ASID, but at this time ASID field in entryHi is 1, and asid_cache(cpu) is 0x100 (it was just reset to ASID_FIRST_VERSION when the secondary TP was booting). So, get_new_mmu_context() increments the asid_cache(cpu) value to 0x101, and thus puts 0x01 into entryHi. The result - ASID field does not get changed as it was supposed to. My solution is very simple - do not reset asid_cache(cpu) on TP warm restart. Patchwork: https://patchwork.linux-mips.org/patch/1797/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
-rw-r--r--arch/mips/kernel/traps.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 261ccbc07740..5c8a49d55054 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1596,7 +1596,8 @@ void __cpuinit per_cpu_trap_init(void)
}
#endif /* CONFIG_MIPS_MT_SMTC */
- cpu_data[cpu].asid_cache = ASID_FIRST_VERSION;
+ if (!cpu_data[cpu].asid_cache)
+ cpu_data[cpu].asid_cache = ASID_FIRST_VERSION;
atomic_inc(&init_mm.mm_count);
current->active_mm = &init_mm;