linux/arch/s390/kernel/trace.c
Heiko Carstens f6c9b16023 s390/diag: avoid lockdep recursion
The diagnose tracer will indirectly call back into the lockdep code
when lockdep does not expect it (arch_spinlock). This causes lockdep
to disable itself and therefore we don't have a working lock
dependency validator anymore.

This patch effectively disables tracing of diag 0x9c and 0x44 if
lockdep is enabled.  If however lockdep is enabled spinlocks are
mainly implemented using a trylock variant, which will not issue any
diag 0x9c or 0x44. So this change has hardly any effect on tracing
except when arch_spinlock and friends are explicitly used.

Reported-and-Tested-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2016-02-11 13:05:56 +01:00

33 lines
671 B
C

/*
* Tracepoint definitions for s390
*
* Copyright IBM Corp. 2015
* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
*/
#include <linux/percpu.h>
#define CREATE_TRACE_POINTS
#include <asm/trace/diag.h>
EXPORT_TRACEPOINT_SYMBOL(s390_diagnose);
static DEFINE_PER_CPU(unsigned int, diagnose_trace_depth);
void trace_s390_diagnose_norecursion(int diag_nr)
{
unsigned long flags;
unsigned int *depth;
/* Avoid lockdep recursion. */
if (IS_ENABLED(CONFIG_LOCKDEP))
return;
local_irq_save(flags);
depth = this_cpu_ptr(&diagnose_trace_depth);
if (*depth == 0) {
(*depth)++;
trace_s390_diagnose(diag_nr);
(*depth)--;
}
local_irq_restore(flags);
}