The following commit has been merged in the linux branch: commit 4f8048ee734dab7c463574797b820c0c68c80791 Author: Heiko Carstens heiko.carstens@de.ibm.com Date: Thu Oct 29 15:04:09 2009 +0100

[S390] smp: fix prefix handling of offlined cpus

Offlined cpus still have valid prefix register contents. Dumpers will store the register contents of a cpu to the location where its prefix register points to. For offlined cpus the area (lowcore) has been freed and the dumper would write the uninteresting contents of the offline cpu to a memory location which might be in use by some other component and destroy valueable information. To fix this set the prefix register of offline cpus to absolute address zero again. This prevents the current dumpers to write to random memory locations.

Signed-off-by: Heiko Carstens heiko.carstens@de.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index c932caa..c699ac5 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -638,6 +638,8 @@ void __cpu_die(unsigned int cpu) /* Wait until target cpu is down */ while (!cpu_stopped(cpu)) cpu_relax(); + while (signal_processor_p(0, cpu, sigp_set_prefix) == sigp_busy) + udelay(10); smp_free_lowcore(cpu); pr_info("Processor %d stopped\n", cpu); }