On Saturday 20 March 2010, Linus Torvalds wrote: > > On Sat, 20 Mar 2010, Peter Zijlstra wrote: > > > > cpuhw = &per_cpu(cpu_hw_events, cpu); > > + if (!cpuhw) > > + return; > > How can an address-of expression be NULL? > > Yes, 'per_cpu()' is magic, but it shouldn't be possible to be _that_ > magic. It's rather against the whole C model. Yeah. A field in the object pointed to by it can be NULL, though. The appended patch fixes the breakage for me too. Rafael --- From: Rafael J. Wysocki <rjw@xxxxxxx> Subject: x86 / perf: Fix suspend to RAM on HP nx6325 Commit 3f6da3905398826d85731247e7fbcf53400c18bd (perf: Rework and fix the arch CPU-hotplug hooks) broke suspend to RAM on my HP nx6325 (and most likely on other AMD-based boxes too) by allowing amd_pmu_cpu_offline() to be executed for CPUs that are going offline as part of the suspend process. The problem is that cpuhw->amd_nb may be NULL already when amd_pmu_cpu_offline() is called, so the function should make sure it's not NULL before accessing the object pointed to by it. Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx> --- arch/x86/kernel/cpu/perf_event_amd.c | 4 ++++ 1 file changed, 4 insertions(+) Index: linux-2.6/arch/x86/kernel/cpu/perf_event_amd.c =================================================================== --- linux-2.6.orig/arch/x86/kernel/cpu/perf_event_amd.c +++ linux-2.6/arch/x86/kernel/cpu/perf_event_amd.c @@ -348,11 +348,15 @@ static void amd_pmu_cpu_offline(int cpu) raw_spin_lock(&amd_nb_lock); + if (!cpuhw->amd_nb) + goto unlock; + if (--cpuhw->amd_nb->refcnt == 0) kfree(cpuhw->amd_nb); cpuhw->amd_nb = NULL; + unlock: raw_spin_unlock(&amd_nb_lock); } _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
