hw-breakpoints: Simplify error handling in breakpoint creation requests

This simplifies the error handling when we create a breakpoint.
We don't need to check the NULL return value corner case anymore
since we have improved perf_event_create_kernel_counter() to
always return an error code in the failure case.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
LKML-Reference: <1259210142-5714-3-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

4 files changed, 7 insertions, 24 deletions

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index b25f8947ed7a..75e0cd847bd6 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -657,10 +657,7 @@ restore:
                                                tsk, true);
                 thread->ptrace_bps[i] = NULL;
 
-                if (!bp) { /* incorrect bp, or we have a bug in bp API */
-                        rc = -EINVAL;
-                        break;
-                }
+                /* Incorrect bp, or we have a bug in bp API */
                 if (IS_ERR(bp)) {
                         rc = PTR_ERR(bp);
                         bp = NULL;
@@ -729,9 +726,6 @@ static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
                                                tsk,
                                                bp->attr.disabled);
         }
-
-        if (!bp)
-                return -EIO;
         /*
          * CHECKME: the previous code returned -EIO if the addr wasn't a
          * valid task virtual addr. The new one will return -EINVAL in this
diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index 06d372fc026d..dd3fb4a999d3 100644
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -442,7 +442,7 @@ register_wide_hw_breakpoint(unsigned long addr,
 
                 *pevent = bp;
 
-                if (IS_ERR(bp) || !bp) {
+                if (IS_ERR(bp)) {
                         err = PTR_ERR(bp);
                         goto fail;
                 }
@@ -453,7 +453,7 @@ register_wide_hw_breakpoint(unsigned long addr,
 fail:
         for_each_possible_cpu(cpu) {
                 pevent = per_cpu_ptr(cpu_events, cpu);
-                if (IS_ERR(*pevent) || !*pevent)
+                if (IS_ERR(*pevent))
                         break;
                 unregister_hw_breakpoint(*pevent);
         }
diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c
index 9f040e42f516..c538b15b95d6 100644
--- a/kernel/trace/trace_ksym.c
+++ b/kernel/trace/trace_ksym.c
@@ -200,12 +200,9 @@ int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
         entry->ksym_hbp = register_wide_hw_breakpoint(entry->ksym_addr,
                                         entry->len, entry->type,
                                         ksym_hbp_handler, true);
+
         if (IS_ERR(entry->ksym_hbp)) {
-                entry->ksym_hbp = NULL;
                 ret = PTR_ERR(entry->ksym_hbp);
-        }
-
-        if (!entry->ksym_hbp) {
                 printk(KERN_INFO "ksym_tracer request failed. Try again"
                                         " later!!\n");
                 goto err;
@@ -332,21 +329,16 @@ static ssize_t ksym_trace_filter_write(struct file *file,
         if (changed) {
                 unregister_wide_hw_breakpoint(entry->ksym_hbp);
                 entry->type = op;
+                ret = 0;
                 if (op > 0) {
                         entry->ksym_hbp =
                                 register_wide_hw_breakpoint(entry->ksym_addr,
                                         entry->len, entry->type,
                                         ksym_hbp_handler, true);
                         if (IS_ERR(entry->ksym_hbp))
-                                entry->ksym_hbp = NULL;
-
-                        /* modified without problem */
-                        if (entry->ksym_hbp) {
-                                ret = 0;
+                                ret = PTR_ERR(entry->ksym_hbp);
+                        else
                                 goto out;
-                        }
-                } else {
-                        ret = 0;
                 }
                 /* Error or "symbol:---" case: drop it */
                 ksym_filter_entry_count--;
diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c
index 95063818bcf4..ee7f9fbaffbd 100644
--- a/samples/hw_breakpoint/data_breakpoint.c
+++ b/samples/hw_breakpoint/data_breakpoint.c
@@ -61,9 +61,6 @@ static int __init hw_break_module_init(void)
         if (IS_ERR(sample_hbp)) {
                 ret = PTR_ERR(sample_hbp);
                 goto fail;
-        } else if (!sample_hbp) {
-                ret = -EINVAL;
-                goto fail;
         }
 
         printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name);