1 files changed, 1 insertions, 25 deletions

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 72edac026a7..5bafdec3444 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -53,7 +53,6 @@
 #include <asm/syscalls.h>
 #include <asm/ds.h>
 #include <asm/debugreg.h>
-#include <asm/hw_breakpoint.h>
 
 asmlinkage extern void ret_from_fork(void);
 
@@ -244,8 +243,6 @@ void release_thread(struct task_struct *dead_task)
                         BUG();
                 }
         }
-        if (unlikely(dead_task->thread.debugreg7))
-                flush_thread_hw_breakpoint(dead_task);
 }
 
 static inline void set_32bit_tls(struct task_struct *t, int tls, u32 addr)
@@ -309,9 +306,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
         savesegment(ds, p->thread.ds);
 
         err = -ENOMEM;
-        if (unlikely(test_tsk_thread_flag(me, TIF_DEBUG)))
-                if (copy_thread_hw_breakpoint(me, p, clone_flags))
-                        goto out;
+        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 
         if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
                 p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
@@ -351,8 +346,6 @@ out:
                 kfree(p->thread.io_bitmap_ptr);
                 p->thread.io_bitmap_max = 0;
         }
-        if (err)
-                flush_thread_hw_breakpoint(p);
 
         return err;
 }
@@ -508,23 +501,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
          */
         if (preload_fpu)
                 __math_state_restore();
-        /*
-         * There's a problem with moving the arch_install_thread_hw_breakpoint()
-         * call before current is updated.  Suppose a kernel breakpoint is
-         * triggered in between the two, the hw-breakpoint handler will see that
-         * the 'current' task does not have TIF_DEBUG flag set and will think it
-         * is leftover from an old task (lazy switching) and will erase it. Then
-         * until the next context switch, no user-breakpoints will be installed.
-         *
-         * The real problem is that it's impossible to update both current and
-         * physical debug registers at the same instant, so there will always be
-         * a window in which they disagree and a breakpoint might get triggered.
-         * Since we use lazy switching, we are forced to assume that a
-         * disagreement means that current is correct and the exception is due
-         * to lazy debug register switching.
-         */
-        if (unlikely(test_tsk_thread_flag(next_p, TIF_DEBUG)))
-                arch_install_thread_hw_breakpoint(next_p);
 
         return prev_p;
 }