Now that the ring buffer is reentrant, some of the ftrace tracers (sched_swich, debugging traces) can also be reentrant. Note: Never make the function tracer reentrant, that can cause recursion problems all over the kernel. The function tracer must disable reentrancy. Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 10 ++-------- kernel/trace/trace_sched_switch.c | 10 ++-------- 2 files changed, 4 insertions(+), 16 deletions(-) Index: linux-tip.git/kernel/trace/trace.c =================================================================== --- linux-tip.git.orig/kernel/trace/trace.c 2008-10-04 01:14:30.000000000 -0400 +++ linux-tip.git/kernel/trace/trace.c 2008-10-04 01:49:35.000000000 -0400 @@ -839,7 +839,6 @@ ftrace_special(unsigned long arg1, unsig { struct trace_array *tr = &global_trace; struct trace_array_cpu *data; - long disabled; int cpu; int pc; @@ -850,12 +849,10 @@ ftrace_special(unsigned long arg1, unsig preempt_disable_notrace(); cpu = raw_smp_processor_id(); data = tr->data[cpu]; - disabled = atomic_inc_return(&data->disabled); - if (likely(disabled == 1)) + if (likely(!atomic_read(&data->disabled))) ftrace_trace_special(tr, data, arg1, arg2, arg3, pc); - atomic_dec(&data->disabled); preempt_enable_notrace(); } @@ -2961,7 +2958,6 @@ int trace_vprintk(unsigned long ip, cons struct trace_array_cpu *data; struct print_entry *entry; unsigned long flags, irq_flags; - long disabled; int cpu, len = 0, size, pc; if (!tr->ctrl || tracing_disabled) @@ -2971,9 +2967,8 @@ int trace_vprintk(unsigned long ip, cons preempt_disable_notrace(); cpu = raw_smp_processor_id(); data = tr->data[cpu]; - disabled = atomic_inc_return(&data->disabled); - if (unlikely(disabled != 1)) + if (unlikely(atomic_read(&data->disabled))) goto out; spin_lock_irqsave(&trace_buf_lock, flags); @@ -2999,7 +2994,6 @@ int trace_vprintk(unsigned long ip, cons spin_unlock_irqrestore(&trace_buf_lock, flags); out: - atomic_dec(&data->disabled); preempt_enable_notrace(); return len; Index: linux-tip.git/kernel/trace/trace_sched_switch.c =================================================================== --- linux-tip.git.orig/kernel/trace/trace_sched_switch.c 2008-10-04 01:14:30.000000000 -0400 +++ linux-tip.git/kernel/trace/trace_sched_switch.c 2008-10-04 01:49:35.000000000 -0400 @@ -24,7 +24,6 @@ probe_sched_switch(struct rq *__rq, stru { struct trace_array_cpu *data; unsigned long flags; - long disabled; int cpu; int pc; @@ -41,12 +40,10 @@ probe_sched_switch(struct rq *__rq, stru local_irq_save(flags); cpu = raw_smp_processor_id(); data = ctx_trace->data[cpu]; - disabled = atomic_inc_return(&data->disabled); - if (likely(disabled == 1)) + if (likely(!atomic_read(&data->disabled))) tracing_sched_switch_trace(ctx_trace, data, prev, next, flags, pc); - atomic_dec(&data->disabled); local_irq_restore(flags); } @@ -55,7 +52,6 @@ probe_sched_wakeup(struct rq *__rq, stru { struct trace_array_cpu *data; unsigned long flags; - long disabled; int cpu, pc; if (!likely(tracer_enabled)) @@ -67,13 +63,11 @@ probe_sched_wakeup(struct rq *__rq, stru local_irq_save(flags); cpu = raw_smp_processor_id(); data = ctx_trace->data[cpu]; - disabled = atomic_inc_return(&data->disabled); - if (likely(disabled == 1)) + if (likely(!atomic_read(&data->disabled))) tracing_sched_wakeup_trace(ctx_trace, data, wakee, current, flags, pc); - atomic_dec(&data->disabled); local_irq_restore(flags); } -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/