kgdb,x86: fix regression in detach handling

The fix from ba773f7c510c0b252145933926c636c439889207
(x86,kgdb: Fix hw breakpoint regression) was not entirely complete.

The kgdb_remove_all_hw_break() function also needs to call the
hw_break_release_slot() or else a breakpoint can get activated again
after the debugger has detached.

The kgdb test suite exposes the behavior in the form of either a hang
or repetitive failure.  The kernel config that exposes the problem
contains all of the following:

CONFIG_DEBUG_RODATA=y
CONFIG_KGDB_TESTS=y
CONFIG_KGDB_TESTS_ON_BOOT=y
CONFIG_KGDB_TESTS_BOOT_STRING="V1F100"

Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Tested-by: Frederic Weisbecker <fweisbec@gmail.com>

diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index ec592ca..cd21b65 100644 (file)
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -315,14 +315,18 @@ static void kgdb_remove_all_hw_break(void)
                if (!breakinfo[i].enabled)
                        continue;
                bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
-               if (bp->attr.disabled == 1)
+               if (!bp->attr.disabled) {
+                       arch_uninstall_hw_breakpoint(bp);
+                       bp->attr.disabled = 1;
                        continue;
+               }
                if (dbg_is_early)
                        early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
                                                 breakinfo[i].type);
-               else
-                       arch_uninstall_hw_breakpoint(bp);
-               bp->attr.disabled = 1;
+               else if (hw_break_release_slot(i))
+                       printk(KERN_ERR "KGDB: hw bpt remove failed %lx\n",
+                              breakinfo[i].addr);
+               breakinfo[i].enabled = 0;
        }
 }