[MIPS] MT: Improved multithreading support.

    
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 60 insertions, 1 deletions

diff --git a/arch/mips/kernel/gdb-stub.c b/arch/mips/kernel/gdb-stub.c
index d4f88e0af24c..6ecbdc1fefd1 100644
--- a/arch/mips/kernel/gdb-stub.c
+++ b/arch/mips/kernel/gdb-stub.c
@@ -140,6 +140,7 @@
 #include <asm/system.h>
 #include <asm/gdb-stub.h>
 #include <asm/inst.h>
+#include <asm/smp.h>
 
 /*
  * external low-level support routines
@@ -669,6 +670,64 @@ static void kgdb_wait(void *arg)
         local_irq_restore(flags);
 }
 
+/*
+ * GDB stub needs to call kgdb_wait on all processor with interrupts
+ * disabled, so it uses it's own special variant.
+ */
+static int kgdb_smp_call_kgdb_wait(void)
+{
+#ifdef CONFIG_SMP
+        struct call_data_struct data;
+        int i, cpus = num_online_cpus() - 1;
+        int cpu = smp_processor_id();
+
+        /*
+         * Can die spectacularly if this CPU isn't yet marked online
+         */
+        BUG_ON(!cpu_online(cpu));
+
+        if (!cpus)
+                return 0;
+
+        if (spin_is_locked(&smp_call_lock)) {
+                /*
+                 * Some other processor is trying to make us do something
+                 * but we're not going to respond... give up
+                 */
+                return -1;
+                }
+
+        /*
+         * We will continue here, accepting the fact that
+         * the kernel may deadlock if another CPU attempts
+         * to call smp_call_function now...
+         */
+
+        data.func = kgdb_wait;
+        data.info = NULL;
+        atomic_set(&data.started, 0);
+        data.wait = 0;
+
+        spin_lock(&smp_call_lock);
+        call_data = &data;
+        mb();
+
+        /* Send a message to all other CPUs and wait for them to respond */
+        for (i = 0; i < NR_CPUS; i++)
+                if (cpu_online(i) && i != cpu)
+                        core_send_ipi(i, SMP_CALL_FUNCTION);
+
+        /* Wait for response */
+        /* FIXME: lock-up detection, backtrace on lock-up */
+        while (atomic_read(&data.started) != cpus)
+                barrier();
+
+        call_data = NULL;
+        spin_unlock(&smp_call_lock);
+#endif
+
+        return 0;
+}
 
 /*
  * This function does all command processing for interfacing to gdb.  It
@@ -718,7 +777,7 @@ void handle_exception (struct gdb_regs *regs)
         /*
          * force other cpus to enter kgdb
          */
-        smp_call_function(kgdb_wait, NULL, 0, 0);
+        kgdb_smp_call_kgdb_wait();
 
         /*
          * If we're in breakpoint() increment the PC