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Heiko Carstens authored
With git commit 4d92f502 ("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>
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