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Diffstat (limited to 'arch/arm/vfp/vfpmodule.c')
-rw-r--r--arch/arm/vfp/vfpmodule.c83
1 files changed, 62 insertions, 21 deletions
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 2d7423af119..aed05bc3c2e 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -38,16 +38,72 @@ union vfp_state *last_VFP_context[NR_CPUS];
*/
unsigned int VFP_arch;
+/*
+ * Per-thread VFP initialization.
+ */
+static void vfp_thread_flush(struct thread_info *thread)
+{
+ union vfp_state *vfp = &thread->vfpstate;
+ unsigned int cpu;
+
+ memset(vfp, 0, sizeof(union vfp_state));
+
+ vfp->hard.fpexc = FPEXC_EN;
+ vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
+
+ /*
+ * Disable VFP to ensure we initialize it first. We must ensure
+ * that the modification of last_VFP_context[] and hardware disable
+ * are done for the same CPU and without preemption.
+ */
+ cpu = get_cpu();
+ if (last_VFP_context[cpu] == vfp)
+ last_VFP_context[cpu] = NULL;
+ fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
+ put_cpu();
+}
+
+static void vfp_thread_release(struct thread_info *thread)
+{
+ /* release case: Per-thread VFP cleanup. */
+ union vfp_state *vfp = &thread->vfpstate;
+ unsigned int cpu = thread->cpu;
+
+ if (last_VFP_context[cpu] == vfp)
+ last_VFP_context[cpu] = NULL;
+}
+
+/*
+ * When this function is called with the following 'cmd's, the following
+ * is true while this function is being run:
+ * THREAD_NOFTIFY_SWTICH:
+ * - the previously running thread will not be scheduled onto another CPU.
+ * - the next thread to be run (v) will not be running on another CPU.
+ * - thread->cpu is the local CPU number
+ * - not preemptible as we're called in the middle of a thread switch
+ * THREAD_NOTIFY_FLUSH:
+ * - the thread (v) will be running on the local CPU, so
+ * v === current_thread_info()
+ * - thread->cpu is the local CPU number at the time it is accessed,
+ * but may change at any time.
+ * - we could be preempted if tree preempt rcu is enabled, so
+ * it is unsafe to use thread->cpu.
+ * THREAD_NOTIFY_RELEASE:
+ * - the thread (v) will not be running on any CPU; it is a dead thread.
+ * - thread->cpu will be the last CPU the thread ran on, which may not
+ * be the current CPU.
+ * - we could be preempted if tree preempt rcu is enabled.
+ */
static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
{
struct thread_info *thread = v;
- union vfp_state *vfp;
- __u32 cpu = thread->cpu;
if (likely(cmd == THREAD_NOTIFY_SWITCH)) {
u32 fpexc = fmrx(FPEXC);
#ifdef CONFIG_SMP
+ unsigned int cpu = thread->cpu;
+
/*
* On SMP, if VFP is enabled, save the old state in
* case the thread migrates to a different CPU. The
@@ -74,25 +130,10 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
return NOTIFY_DONE;
}
- vfp = &thread->vfpstate;
- if (cmd == THREAD_NOTIFY_FLUSH) {
- /*
- * Per-thread VFP initialisation.
- */
- memset(vfp, 0, sizeof(union vfp_state));
-
- vfp->hard.fpexc = FPEXC_EN;
- vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
-
- /*
- * Disable VFP to ensure we initialise it first.
- */
- fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
- }
-
- /* flush and release case: Per-thread VFP cleanup. */
- if (last_VFP_context[cpu] == vfp)
- last_VFP_context[cpu] = NULL;
+ if (cmd == THREAD_NOTIFY_FLUSH)
+ vfp_thread_flush(thread);
+ else
+ vfp_thread_release(thread);
return NOTIFY_DONE;
}