Commit-ID: 3189cdb31622f4e40688ce5a6fc5d940b42bc805 Gitweb: http://git.kernel.org/tip/3189cdb31622f4e40688ce5a6fc5d940b42bc805 Author: Steven Rostedt <srostedt@xxxxxxxxxx> AuthorDate: Fri, 17 Apr 2009 16:13:55 -0400 Committer: Steven Rostedt <rostedt@xxxxxxxxxxx> CommitDate: Fri, 17 Apr 2009 16:21:35 -0400 tracing: protect trace_printk from recursion trace_printk can be called from any context, including NMIs. If this happens, then we must test for for recursion before grabbing any spinlocks. This patch prevents trace_printk from being called recursively. [ Impact: prevent hard lockup in lockdep event tracer ] Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> --- kernel/trace/trace.c | 10 ++++++++-- 1 files changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 183d788..b9a3adc 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1259,6 +1259,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args) struct trace_array_cpu *data; struct bprint_entry *entry; unsigned long flags; + int disable; int resched; int cpu, len = 0, size, pc; @@ -1273,7 +1274,8 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args) cpu = raw_smp_processor_id(); data = tr->data[cpu]; - if (unlikely(atomic_read(&data->disabled))) + disable = atomic_inc_return(&data->disabled); + if (unlikely(disable != 1)) goto out; /* Lockdep uses trace_printk for lock tracing */ @@ -1301,6 +1303,7 @@ out_unlock: local_irq_restore(flags); out: + atomic_dec_return(&data->disabled); ftrace_preempt_enable(resched); unpause_graph_tracing(); @@ -1320,6 +1323,7 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) int cpu, len = 0, size, pc; struct print_entry *entry; unsigned long irq_flags; + int disable; if (tracing_disabled || tracing_selftest_running) return 0; @@ -1329,7 +1333,8 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) cpu = raw_smp_processor_id(); data = tr->data[cpu]; - if (unlikely(atomic_read(&data->disabled))) + disable = atomic_inc_return(&data->disabled); + if (unlikely(disable != 1)) goto out; pause_graph_tracing(); @@ -1357,6 +1362,7 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) raw_local_irq_restore(irq_flags); unpause_graph_tracing(); out: + atomic_dec_return(&data->disabled); preempt_enable_notrace(); return len; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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