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authorDavid Daney <david.daney@cavium.com>2015-08-03 17:48:43 -0700
committerRalf Baechle <ralf@linux-mips.org>2015-08-05 11:11:10 +0200
commit46011e6ea39235e4aca656673c500eac81a07a17 (patch)
tree40c529d5bb47cc8fc7380df3ac4e918fd76852b3
parenta4504755e7dc8d43ed2a934397032691cd03adf7 (diff)
MIPS: Make set_pte() SMP safe.
On MIPS the GLOBAL bit of the PTE must have the same value in any aligned pair of PTEs. These pairs of PTEs are referred to as "buddies". In a SMP system is is possible for two CPUs to be calling set_pte() on adjacent PTEs at the same time. There is a race between setting the PTE and a different CPU setting the GLOBAL bit in its buddy PTE. This race can be observed when multiple CPUs are executing vmap()/vfree() at the same time. Make setting the buddy PTE's GLOBAL bit an atomic operation to close the race condition. The case of CONFIG_64BIT_PHYS_ADDR && CONFIG_CPU_MIPS32 is *not* handled. Signed-off-by: David Daney <david.daney@cavium.com> Cc: <stable@vger.kernel.org> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/10835/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
-rw-r--r--arch/mips/include/asm/pgtable.h31
1 files changed, 31 insertions, 0 deletions
diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index 9d8106758142..ae8569475264 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -182,8 +182,39 @@ static inline void set_pte(pte_t *ptep, pte_t pteval)
* Make sure the buddy is global too (if it's !none,
* it better already be global)
*/
+#ifdef CONFIG_SMP
+ /*
+ * For SMP, multiple CPUs can race, so we need to do
+ * this atomically.
+ */
+#ifdef CONFIG_64BIT
+#define LL_INSN "lld"
+#define SC_INSN "scd"
+#else /* CONFIG_32BIT */
+#define LL_INSN "ll"
+#define SC_INSN "sc"
+#endif
+ unsigned long page_global = _PAGE_GLOBAL;
+ unsigned long tmp;
+
+ __asm__ __volatile__ (
+ " .set push\n"
+ " .set noreorder\n"
+ "1: " LL_INSN " %[tmp], %[buddy]\n"
+ " bnez %[tmp], 2f\n"
+ " or %[tmp], %[tmp], %[global]\n"
+ " " SC_INSN " %[tmp], %[buddy]\n"
+ " beqz %[tmp], 1b\n"
+ " nop\n"
+ "2:\n"
+ " .set pop"
+ : [buddy] "+m" (buddy->pte),
+ [tmp] "=&r" (tmp)
+ : [global] "r" (page_global));
+#else /* !CONFIG_SMP */
if (pte_none(*buddy))
pte_val(*buddy) = pte_val(*buddy) | _PAGE_GLOBAL;
+#endif /* CONFIG_SMP */
}
#endif
}