x86 mmiotrace: improve handling of secondary faults
authorStuart Bennett <stuart@freedesktop.org>
Thu, 5 Feb 2009 11:02:02 +0000 (11:02 +0000)
committerIngo Molnar <mingo@elte.hu>
Mon, 2 Mar 2009 09:20:37 +0000 (10:20 +0100)
Upgrade some kmmio.c debug messages to warnings.
Allow secondary faults on probed pages to fall through, and only log
secondary faults that are not due to non-present pages.

Patch edited by Pekka Paalanen.

Signed-off-by: Stuart Bennett <stuart@freedesktop.org>
Signed-off-by: Pekka Paalanen <pq@iki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
arch/x86/mm/kmmio.c

index d29777520af332908f260f113f915c98c0cbb6a6..4c66bd3a240d93f9d4436187e014cea7a63b2428 100644 (file)
@@ -232,28 +232,32 @@ int kmmio_handler(struct pt_regs *regs, unsigned long addr)
 
        ctx = &get_cpu_var(kmmio_ctx);
        if (ctx->active) {
-               disarm_kmmio_fault_page(faultpage);
                if (addr == ctx->addr) {
                        /*
-                        * On SMP we sometimes get recursive probe hits on the
-                        * same address. Context is already saved, fall out.
+                        * A second fault on the same page means some other
+                        * condition needs handling by do_page_fault(), the
+                        * page really not being present is the most common.
                         */
-                       pr_debug("kmmio: duplicate probe hit on CPU %d, for "
-                                               "address 0x%08lx.\n",
-                                               smp_processor_id(), addr);
-                       ret = 1;
-                       goto no_kmmio_ctx;
-               }
-               /*
-                * Prevent overwriting already in-flight context.
-                * This should not happen, let's hope disarming at least
-                * prevents a panic.
-                */
-               pr_emerg("kmmio: recursive probe hit on CPU %d, "
+                       pr_debug("kmmio: secondary hit for 0x%08lx CPU %d.\n",
+                                       addr, smp_processor_id());
+
+                       if (!faultpage->old_presence)
+                               pr_info("kmmio: unexpected secondary hit for "
+                                       "address 0x%08lx on CPU %d.\n", addr,
+                                       smp_processor_id());
+               } else {
+                       /*
+                        * Prevent overwriting already in-flight context.
+                        * This should not happen, let's hope disarming at
+                        * least prevents a panic.
+                        */
+                       pr_emerg("kmmio: recursive probe hit on CPU %d, "
                                        "for address 0x%08lx. Ignoring.\n",
                                        smp_processor_id(), addr);
-               pr_emerg("kmmio: previous hit was at 0x%08lx.\n",
-                                       ctx->addr);
+                       pr_emerg("kmmio: previous hit was at 0x%08lx.\n",
+                                               ctx->addr);
+                       disarm_kmmio_fault_page(faultpage);
+               }
                goto no_kmmio_ctx;
        }
        ctx->active++;
@@ -305,7 +309,7 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
        struct kmmio_context *ctx = &get_cpu_var(kmmio_ctx);
 
        if (!ctx->active) {
-               pr_debug("kmmio: spurious debug trap on CPU %d.\n",
+               pr_warning("kmmio: spurious debug trap on CPU %d.\n",
                                                        smp_processor_id());
                goto out;
        }