Merge branch 'android-4.4' of https://android.googlesource.com/kernel/common

[firefly-linux-kernel-4.4.55.git] / arch / powerpc / kernel / process.c

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index a7b91b54c8134d3f94ce2c2a1dce9b38db30ad59..36795d1e75586aa523f2c55ffabc09baeb1562f1 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -551,6 +551,24 @@ static void tm_reclaim_thread(struct thread_struct *thr,
                msr_diff &= MSR_FP | MSR_VEC | MSR_VSX | MSR_FE0 | MSR_FE1;
        }
 
+       /*
+        * Use the current MSR TM suspended bit to track if we have
+        * checkpointed state outstanding.
+        * On signal delivery, we'd normally reclaim the checkpointed
+        * state to obtain stack pointer (see:get_tm_stackpointer()).
+        * This will then directly return to userspace without going
+        * through __switch_to(). However, if the stack frame is bad,
+        * we need to exit this thread which calls __switch_to() which
+        * will again attempt to reclaim the already saved tm state.
+        * Hence we need to check that we've not already reclaimed
+        * this state.
+        * We do this using the current MSR, rather tracking it in
+        * some specific thread_struct bit, as it has the additional
+        * benifit of checking for a potential TM bad thing exception.
+        */
+       if (!MSR_TM_SUSPENDED(mfmsr()))
+               return;
+
        /*
         * Use the current MSR TM suspended bit to track if we have
         * checkpointed state outstanding.