diff options
| author | David Daney <david.daney@cavium.com> | 2015-08-03 17:48:43 -0700 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2015-08-19 13:15:59 -0400 |
| commit | 204041c4a640f004a5df152434f05b96ee76dfab (patch) | |
| tree | df72491f918b872aadd5875d98a1d019b60fda52 /arch | |
| parent | e1c3e51cf7e1de53b9279ac6a02ceb8630dd15f2 (diff) | |
MIPS: Make set_pte() SMP safe.
[ Upstream commit 46011e6ea39235e4aca656673c500eac81a07a17 ]
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>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/mips/include/asm/pgtable.h | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h index bc3fc4fdc9ab..060fc2e50cd2 100644 --- a/arch/mips/include/asm/pgtable.h +++ b/arch/mips/include/asm/pgtable.h @@ -187,8 +187,39 @@ 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 } |