1 files changed, 15 insertions, 5 deletions

diff --git a/kernel/kgdb.c b/kernel/kgdb.c
index 29357a9ccfb2..ca21fe98e8de 100644
--- a/kernel/kgdb.c
+++ b/kernel/kgdb.c
@@ -129,6 +129,7 @@ struct task_struct		*kgdb_usethread;
 struct task_struct              *kgdb_contthread;
 
 int                             kgdb_single_step;
+pid_t                           kgdb_sstep_pid;
 
 /* Our I/O buffers. */
 static char                     remcom_in_buffer[BUFMAX];
@@ -1400,6 +1401,7 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
         struct kgdb_state kgdb_var;
         struct kgdb_state *ks = &kgdb_var;
         unsigned long flags;
+        int sstep_tries = 100;
         int error = 0;
         int i, cpu;
 
@@ -1430,13 +1432,14 @@ acquirelock:
                 cpu_relax();
 
         /*
-         * Do not start the debugger connection on this CPU if the last
-         * instance of the exception handler wanted to come into the
-         * debugger on a different CPU via a single step
+         * For single stepping, try to only enter on the processor
+         * that was single stepping.  To gaurd against a deadlock, the
+         * kernel will only try for the value of sstep_tries before
+         * giving up and continuing on.
          */
         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
-            atomic_read(&kgdb_cpu_doing_single_step) != cpu) {
-
+            (kgdb_info[cpu].task &&
+             kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
                 atomic_set(&kgdb_active, -1);
                 touch_softlockup_watchdog();
                 clocksource_touch_watchdog();
@@ -1529,6 +1532,13 @@ acquirelock:
         }
 
 kgdb_restore:
+        if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
+                int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
+                if (kgdb_info[sstep_cpu].task)
+                        kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
+                else
+                        kgdb_sstep_pid = 0;
+        }
         /* Free kgdb_active */
         atomic_set(&kgdb_active, -1);
         touch_softlockup_watchdog();