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authorSteven Rostedt <rostedt@goodmis.org>2008-05-12 21:20:54 +0200
committerThomas Gleixner <tglx@linutronix.de>2008-05-23 21:13:02 +0200
commit4fe8c3048cd8280a54256bca9cac2007bd546c33 (patch)
treeb6bba481a3dde79a027654675d3b34da24ca54f2 /kernel
parent8f96da02c14d722ad9a3713cd7273ce28c9036ad (diff)
ftrace: printk and trace irqsoff and wakeups
printk called from wakeup critical timings and irqs off can cause deadlocks since printk might do a wakeup itself. If the call to printk happens with the runqueue lock held, it can deadlock. This patch protects the printk from being called in trace irqs off with a test to see if the runqueue for the current CPU is locked. If it is locked, the printk is skipped. The wakeup always holds the runqueue lock, so the printk is simply removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace_irqsoff.c26
-rw-r--r--kernel/trace/trace_sched_wakeup.c13
2 files changed, 14 insertions, 25 deletions
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 7a4dc014b8a..d0c1748b1e2 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -165,18 +165,20 @@ check_critical_timing(struct trace_array *tr,
update_max_tr_single(tr, current, cpu);
- if (tracing_thresh) {
- printk(KERN_INFO "(%16s-%-5d|#%d):"
- " %lu us critical section violates %lu us threshold.\n",
- current->comm, current->pid,
- raw_smp_processor_id(),
- latency, nsecs_to_usecs(tracing_thresh));
- } else {
- printk(KERN_INFO "(%16s-%-5d|#%d):"
- " new %lu us maximum-latency critical section.\n",
- current->comm, current->pid,
- raw_smp_processor_id(),
- latency);
+ if (!runqueue_is_locked()) {
+ if (tracing_thresh) {
+ printk(KERN_INFO "(%16s-%-5d|#%d): %lu us critical"
+ " section violates %lu us threshold.\n",
+ current->comm, current->pid,
+ raw_smp_processor_id(),
+ latency, nsecs_to_usecs(tracing_thresh));
+ } else {
+ printk(KERN_INFO "(%16s-%-5d|#%d): new %lu us"
+ " maximum-latency critical section.\n",
+ current->comm, current->pid,
+ raw_smp_processor_id(),
+ latency);
+ }
}
max_sequence++;
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 2a012423f9d..5948011006b 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -106,19 +106,6 @@ wakeup_sched_switch(struct task_struct *prev, struct task_struct *next)
update_max_tr(tr, wakeup_task, wakeup_cpu);
- if (tracing_thresh) {
- printk(KERN_INFO "(%16s-%-5d|#%d):"
- " %lu us wakeup latency violates %lu us threshold.\n",
- wakeup_task->comm, wakeup_task->pid,
- raw_smp_processor_id(),
- latency, nsecs_to_usecs(tracing_thresh));
- } else {
- printk(KERN_INFO "(%16s-%-5d|#%d):"
- " new %lu us maximum wakeup latency.\n",
- wakeup_task->comm, wakeup_task->pid,
- cpu, latency);
- }
-
out_unlock:
__wakeup_reset(tr);
spin_unlock_irqrestore(&wakeup_lock, flags);