[Patch 2/2] ksym_tracer:Handle machine stall when cat trace_pipe for ksym tracer

["K.Prasad" <prasad@linux.vnet.ibm.com>]

[-- Attachment #1: fix_machine_stall_issue_02 --]
[-- Type: text/plain, Size: 1019 bytes --]

'trace_pipe' does not handle a TRACE_TYPE_PARTIAL_LINE well and causes the
machine to stall. While a TRACE_TYPE_UNHANDLED return causes the tracer to
output unrelated data, a TRACE_TYPE_HANDLED return presents a clean output
(minus all partial traces).

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
---
 kernel/trace/trace_ksym.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-2.6-tip.hbkpt/kernel/trace/trace_ksym.c
===================================================================
--- linux-2.6-tip.hbkpt.orig/kernel/trace/trace_ksym.c
+++ linux-2.6-tip.hbkpt/kernel/trace/trace_ksym.c
@@ -389,6 +389,12 @@ static enum print_line_t ksym_trace_outp
 
 	trace_assign_type(field, entry);
 
+	/*
+	 * Return early without any output if we don't have sufficient
+	 * information
+	 */
+	if ((!field->ksym_hbp->info.type) || (!field->ip))
+		return TRACE_TYPE_HANDLED;
 	ret = trace_seq_printf(s, "%-15s %-5d %-3d %-20s ", field->p_name,
 				entry->pid, iter->cpu, field->ksym_name);
 	if (!ret) {