MIPS: oprofile: Fix BUG due to smp_processor_id() in preemptible code.

current_cpu_type() is not preemption-safe.
If CONFIG_PREEMPT is enabled then mipsxx_reg_setup() can be called from preemptible state.
Added get_cpu()/put_cpu() pair to make it preemption-safe.

This was found while testing oprofile with CONFIG_DEBUG_PREEMPT enable.

/usr/zntestsuite # opcontrol --init
/usr/zntestsuite # opcontrol --setup --event=L2_CACHE_ACCESSES:500 --event=L2_CACHE_MISSES:500 --no-vmlinux
/usr/zntestsuite # opcontrol --start
Using 2.6+ OProfile kernel interface.
BUG: using smp_processor_id() in preemptible [00000000] code: oprofiled/1362
caller is mipsxx_reg_setup+0x11c/0x164
CPU: 0 PID: 1362 Comm: oprofiled Not tainted 3.10.4 #18
Stack : 00000006 70757465 00000000 00000000 00000000 00000000 80b173f6 00000037
          80b10000 00000000 80b21614 88f5a220 00000000 00000000 00000000 00000000
          00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
          00000000 00000000 00000000 89c49c00 89c49c2c 80721254 807b7927 8012c1d0
          80b10000 80721254 00000000 00000552 88f5a220 80b1335c 807b78e6 89c49ba8
          ...
Call Trace:
[<801099a4>] show_stack+0x64/0x7c
[<80665520>] dump_stack+0x20/0x2c
[<803a2250>] debug_smp_processor_id+0xe0/0xf0
[<8052df24>] mipsxx_reg_setup+0x11c/0x164
[<8052cd70>] op_mips_setup+0x24/0x4c
[<80529cfc>] oprofile_setup+0x5c/0x12c
[<8052b9f8>] event_buffer_open+0x78/0xf8
[<801c3150>] do_dentry_open.isra.15+0x2b8/0x3b0
[<801c3270>] finish_open+0x28/0x4c
[<801d49b8>] do_last.isra.41+0x2cc/0xd00
[<801d54a0>] path_openat+0xb4/0x4c4
[<801d5c44>] do_filp_open+0x3c/0xac
[<801c4744>] do_sys_open+0x110/0x1f4
[<8010f47c>] stack_done+0x20/0x44

Bug reported and original patch by Jerin Jacob <jerinjacobk@gmail.com>.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Acked-by: Jerin Jacob <jerinjacobk@gmail.com>

diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
index 1dc086087a723fd9c90c427d05f4eb3c8ca919f6..fa44f3ec530214f5014664cda4611b1a5a027251 100644 (file)
--- a/arch/mips/include/asm/cpu-features.h
+++ b/arch/mips/include/asm/cpu-features.h
@@ -17,6 +17,8 @@
 #define current_cpu_type()     current_cpu_data.cputype
 #endif
 
+#define boot_cpu_type()                cpu_data[0].cputype
+
 /*
  * SMP assumption: Options of CPU 0 are a superset of all processors.
  * This is true for all known MIPS systems.

diff --git a/arch/mips/oprofile/op_model_mipsxx.c b/arch/mips/oprofile/op_model_mipsxx.c
index e4b1140cdae060dca0de8bfdd6a5985b1429de58..3a2b6e9f25cfb95ab0f2f5ee1eeccf069bde8f22 100644 (file)
--- a/arch/mips/oprofile/op_model_mipsxx.c
+++ b/arch/mips/oprofile/op_model_mipsxx.c
@@ -166,7 +166,7 @@ static void mipsxx_reg_setup(struct op_counter_config *ctr)
                        reg.control[i] |= M_PERFCTL_USER;
                if (ctr[i].exl)
                        reg.control[i] |= M_PERFCTL_EXL;
-               if (current_cpu_type() == CPU_XLR)
+               if (boot_cpu_type() == CPU_XLR)
                        reg.control[i] |= M_PERFCTL_COUNT_ALL_THREADS;
                reg.counter[i] = 0x80000000 - ctr[i].count;
        }