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authorHeiko Carstens <heiko.carstens@de.ibm.com>2015-02-28 11:35:26 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2015-03-02 11:35:53 -0800
commita9ca8eb7afb4f1c90d8e43092e94c4e86785efbc (patch)
tree0e728829761cb824e4e470e1429d7144027a4c6c /arch/s390
parentd94260832d0d78aba398de361c0416a93cabc046 (diff)
s390/ftrace: fix crashes when switching tracers / add notrace to cpu_relax()
With git commit 4d92f50249eb ("s390: reintroduce diag 44 calls for cpu_relax()") I reintroduced a non-trivial cpu_relax() variant on s390. The difference to the previous variant however is that the new version is an out-of-line function, which will be traced if function tracing is enabled. Switching to different tracers includes instruction patching. Therefore this is done within stop_machine() "context" to prevent that any function tracing is going on while instructions are being patched. With the new out-of-line variant of cpu_relax() this is not true anymore, since cpu_relax() gets called in a busy loop by all waiting cpus within stop_machine() until function patching is finished. Therefore cpu_relax() must be marked notrace. This fixes kernel crashes when frequently switching between "function" and "function_graph" tracers. Moving cpu_relax() to a header file again, doesn't work because of header include order dependencies. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/kernel/processor.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/s390/kernel/processor.c b/arch/s390/kernel/processor.c
index 26108232fcaa..dc488e13b7e3 100644
--- a/arch/s390/kernel/processor.c
+++ b/arch/s390/kernel/processor.c
@@ -18,7 +18,7 @@
static DEFINE_PER_CPU(struct cpuid, cpu_id);
-void cpu_relax(void)
+void notrace cpu_relax(void)
{
if (!smp_cpu_mtid && MACHINE_HAS_DIAG44)
asm volatile("diag 0,0,0x44");