From: Aboorva Devarajan Date: Fri, 5 Jun 2026 08:29:12 +0000 (+0530) Subject: powerpc/kexec: fix double get_cpu() imbalance in kexec_prepare_cpus X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5c86f1c1f972761a04bf22f4c0618d1aa714185b;p=thirdparty%2Flinux.git powerpc/kexec: fix double get_cpu() imbalance in kexec_prepare_cpus kexec_prepare_cpus_wait() calls get_cpu() internally to obtain the current CPU id. kexec_prepare_cpus() calls kexec_prepare_cpus_wait() twice -- once for KEXEC_STATE_IRQS_OFF and once for KEXEC_STATE_REAL_MODE -- but only issues a single put_cpu() at the end, leaving preempt_count elevated by one extra nesting level. In practice the imbalance does not trigger a 'scheduling while atomic' splat because the kexec path is a one-way trip: IRQs are already disabled, no schedule() occurs after the leak, and default_machine_kexec() overwrites preempt_count with HARDIRQ_OFFSET before jumping into kexec_sequence() which never returns. However the bookkeeping is still wrong. kexec_prepare_cpus() calls local_irq_disable()/hard_irq_disable() before invoking kexec_prepare_cpus_wait(), so the CPU is already pinned and the get_cpu()/put_cpu() preempt_disable() bracketing is unnecessary. Only the current CPU id is needed, so replace get_cpu() with raw_smp_processor_id() and drop the now-unneeded put_cpu(). Fixes: 1fc711f7ffb0 ("powerpc/kexec: Fix race in kexec shutdown") Signed-off-by: Aboorva Devarajan Reviewed-by: Shrikanth Hegde Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20260605082912.305100-4-aboorvad@linux.ibm.com --- diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c index 825ab8a88f18e..58c13a59b93b5 100644 --- a/arch/powerpc/kexec/core_64.c +++ b/arch/powerpc/kexec/core_64.c @@ -169,7 +169,7 @@ static void kexec_prepare_cpus_wait(int wait_state) int my_cpu, i, notified=-1; hw_breakpoint_disable(); - my_cpu = get_cpu(); + my_cpu = raw_smp_processor_id(); /* Make sure each CPU has at least made it to the state we need. * * FIXME: There is a (slim) chance of a problem if not all of the CPUs @@ -267,8 +267,6 @@ static void kexec_prepare_cpus(void) /* after we tell the others to go down */ if (ppc_md.kexec_cpu_down) ppc_md.kexec_cpu_down(0, 0); - - put_cpu(); } #else /* ! SMP */