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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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011e4b02f1
If we try to perform a kexec when the machine is in ST (Single-Threaded) mode (ppc64_cpu --smt=off), the kexec operation doesn't succeed properly, and we get the following messages during boot: [ 0.089866] POWER8 performance monitor hardware support registered [ 0.089985] power8-pmu: PMAO restore workaround active. [ 5.095419] Processor 1 is stuck. [ 10.097933] Processor 2 is stuck. [ 15.100480] Processor 3 is stuck. [ 20.102982] Processor 4 is stuck. [ 25.105489] Processor 5 is stuck. [ 30.108005] Processor 6 is stuck. [ 35.110518] Processor 7 is stuck. [ 40.113369] Processor 9 is stuck. [ 45.115879] Processor 10 is stuck. [ 50.118389] Processor 11 is stuck. [ 55.120904] Processor 12 is stuck. [ 60.123425] Processor 13 is stuck. [ 65.125970] Processor 14 is stuck. [ 70.128495] Processor 15 is stuck. [ 75.131316] Processor 17 is stuck. Note that only the sibling threads are stuck, while the primary threads (0, 8, 16 etc) boot just fine. Looking closer at the previous step of kexec, we observe that kexec tries to wakeup (bring online) the sibling threads of all the cores, before performing kexec: [ 9464.131231] Starting new kernel [ 9464.148507] kexec: Waking offline cpu 1. [ 9464.148552] kexec: Waking offline cpu 2. [ 9464.148600] kexec: Waking offline cpu 3. [ 9464.148636] kexec: Waking offline cpu 4. [ 9464.148671] kexec: Waking offline cpu 5. [ 9464.148708] kexec: Waking offline cpu 6. [ 9464.148743] kexec: Waking offline cpu 7. [ 9464.148779] kexec: Waking offline cpu 9. [ 9464.148815] kexec: Waking offline cpu 10. [ 9464.148851] kexec: Waking offline cpu 11. [ 9464.148887] kexec: Waking offline cpu 12. [ 9464.148922] kexec: Waking offline cpu 13. [ 9464.148958] kexec: Waking offline cpu 14. [ 9464.148994] kexec: Waking offline cpu 15. [ 9464.149030] kexec: Waking offline cpu 17. Instrumenting this piece of code revealed that the cpu_up() operation actually fails with -EBUSY. Thus, only the primary threads of all the cores are online during kexec, and hence this is a sure-shot receipe for disaster, as explained in commite8e5c2155b
(powerpc/kexec: Fix orphaned offline CPUs across kexec), as well as in the comment above wake_offline_cpus(). It turns out that cpu_up() was returning -EBUSY because the variable 'cpu_hotplug_disabled' was set to 1; and this disabling of CPU hotplug was done by migrate_to_reboot_cpu() inside kernel_kexec(). Now, migrate_to_reboot_cpu() was originally written with the assumption that any further code will not need to perform CPU hotplug, since we are anyway in the reboot path. However, kexec is clearly not such a case, since we depend on onlining CPUs, atleast on powerpc. So re-enable cpu-hotplug after returning from migrate_to_reboot_cpu() in the kexec path, to fix this regression in kexec on powerpc. Also, wrap the cpu_up() in powerpc kexec code within a WARN_ON(), so that we can catch such issues more easily in the future. Fixes:c97102ba96
(kexec: migrate to reboot cpu) Cc: stable@vger.kernel.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
416 lines
11 KiB
C
416 lines
11 KiB
C
/*
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* PPC64 code to handle Linux booting another kernel.
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*
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* Copyright (C) 2004-2005, IBM Corp.
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*
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* Created by: Milton D Miller II
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*
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* This source code is licensed under the GNU General Public License,
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* Version 2. See the file COPYING for more details.
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*/
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#include <linux/kexec.h>
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#include <linux/smp.h>
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#include <linux/thread_info.h>
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#include <linux/init_task.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/cpu.h>
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#include <linux/hardirq.h>
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#include <asm/page.h>
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#include <asm/current.h>
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#include <asm/machdep.h>
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#include <asm/cacheflush.h>
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#include <asm/paca.h>
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#include <asm/mmu.h>
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#include <asm/sections.h> /* _end */
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#include <asm/prom.h>
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#include <asm/smp.h>
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#include <asm/hw_breakpoint.h>
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int default_machine_kexec_prepare(struct kimage *image)
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{
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int i;
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unsigned long begin, end; /* limits of segment */
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unsigned long low, high; /* limits of blocked memory range */
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struct device_node *node;
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const unsigned long *basep;
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const unsigned int *sizep;
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if (!ppc_md.hpte_clear_all)
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return -ENOENT;
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/*
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* Since we use the kernel fault handlers and paging code to
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* handle the virtual mode, we must make sure no destination
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* overlaps kernel static data or bss.
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*/
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for (i = 0; i < image->nr_segments; i++)
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if (image->segment[i].mem < __pa(_end))
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return -ETXTBSY;
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/*
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* For non-LPAR, we absolutely can not overwrite the mmu hash
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* table, since we are still using the bolted entries in it to
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* do the copy. Check that here.
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*
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* It is safe if the end is below the start of the blocked
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* region (end <= low), or if the beginning is after the
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* end of the blocked region (begin >= high). Use the
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* boolean identity !(a || b) === (!a && !b).
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*/
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if (htab_address) {
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low = __pa(htab_address);
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high = low + htab_size_bytes;
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for (i = 0; i < image->nr_segments; i++) {
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begin = image->segment[i].mem;
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end = begin + image->segment[i].memsz;
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if ((begin < high) && (end > low))
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return -ETXTBSY;
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}
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}
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/* We also should not overwrite the tce tables */
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for_each_node_by_type(node, "pci") {
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basep = of_get_property(node, "linux,tce-base", NULL);
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sizep = of_get_property(node, "linux,tce-size", NULL);
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if (basep == NULL || sizep == NULL)
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continue;
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low = *basep;
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high = low + (*sizep);
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for (i = 0; i < image->nr_segments; i++) {
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begin = image->segment[i].mem;
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end = begin + image->segment[i].memsz;
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if ((begin < high) && (end > low))
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return -ETXTBSY;
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}
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}
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return 0;
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}
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#define IND_FLAGS (IND_DESTINATION | IND_INDIRECTION | IND_DONE | IND_SOURCE)
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static void copy_segments(unsigned long ind)
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{
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unsigned long entry;
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unsigned long *ptr;
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void *dest;
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void *addr;
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/*
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* We rely on kexec_load to create a lists that properly
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* initializes these pointers before they are used.
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* We will still crash if the list is wrong, but at least
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* the compiler will be quiet.
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*/
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ptr = NULL;
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dest = NULL;
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for (entry = ind; !(entry & IND_DONE); entry = *ptr++) {
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addr = __va(entry & PAGE_MASK);
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switch (entry & IND_FLAGS) {
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case IND_DESTINATION:
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dest = addr;
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break;
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case IND_INDIRECTION:
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ptr = addr;
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break;
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case IND_SOURCE:
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copy_page(dest, addr);
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dest += PAGE_SIZE;
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}
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}
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}
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void kexec_copy_flush(struct kimage *image)
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{
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long i, nr_segments = image->nr_segments;
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struct kexec_segment ranges[KEXEC_SEGMENT_MAX];
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/* save the ranges on the stack to efficiently flush the icache */
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memcpy(ranges, image->segment, sizeof(ranges));
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/*
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* After this call we may not use anything allocated in dynamic
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* memory, including *image.
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*
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* Only globals and the stack are allowed.
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*/
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copy_segments(image->head);
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/*
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* we need to clear the icache for all dest pages sometime,
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* including ones that were in place on the original copy
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*/
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for (i = 0; i < nr_segments; i++)
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flush_icache_range((unsigned long)__va(ranges[i].mem),
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(unsigned long)__va(ranges[i].mem + ranges[i].memsz));
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}
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#ifdef CONFIG_SMP
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static int kexec_all_irq_disabled = 0;
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static void kexec_smp_down(void *arg)
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{
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local_irq_disable();
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hard_irq_disable();
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mb(); /* make sure our irqs are disabled before we say they are */
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get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;
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while(kexec_all_irq_disabled == 0)
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cpu_relax();
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mb(); /* make sure all irqs are disabled before this */
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hw_breakpoint_disable();
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/*
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* Now every CPU has IRQs off, we can clear out any pending
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* IPIs and be sure that no more will come in after this.
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*/
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if (ppc_md.kexec_cpu_down)
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ppc_md.kexec_cpu_down(0, 1);
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kexec_smp_wait();
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/* NOTREACHED */
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}
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static void kexec_prepare_cpus_wait(int wait_state)
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{
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int my_cpu, i, notified=-1;
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hw_breakpoint_disable();
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my_cpu = get_cpu();
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/* Make sure each CPU has at least made it to the state we need.
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*
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* FIXME: There is a (slim) chance of a problem if not all of the CPUs
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* are correctly onlined. If somehow we start a CPU on boot with RTAS
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* start-cpu, but somehow that CPU doesn't write callin_cpu_map[] in
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* time, the boot CPU will timeout. If it does eventually execute
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* stuff, the secondary will start up (paca[].cpu_start was written) and
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* get into a peculiar state. If the platform supports
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* smp_ops->take_timebase(), the secondary CPU will probably be spinning
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* in there. If not (i.e. pseries), the secondary will continue on and
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* try to online itself/idle/etc. If it survives that, we need to find
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* these possible-but-not-online-but-should-be CPUs and chaperone them
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* into kexec_smp_wait().
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*/
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for_each_online_cpu(i) {
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if (i == my_cpu)
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continue;
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while (paca[i].kexec_state < wait_state) {
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barrier();
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if (i != notified) {
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printk(KERN_INFO "kexec: waiting for cpu %d "
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"(physical %d) to enter %i state\n",
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i, paca[i].hw_cpu_id, wait_state);
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notified = i;
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}
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}
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}
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mb();
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}
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/*
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* We need to make sure each present CPU is online. The next kernel will scan
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* the device tree and assume primary threads are online and query secondary
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* threads via RTAS to online them if required. If we don't online primary
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* threads, they will be stuck. However, we also online secondary threads as we
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* may be using 'cede offline'. In this case RTAS doesn't see the secondary
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* threads as offline -- and again, these CPUs will be stuck.
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*
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* So, we online all CPUs that should be running, including secondary threads.
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*/
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static void wake_offline_cpus(void)
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{
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int cpu = 0;
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for_each_present_cpu(cpu) {
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if (!cpu_online(cpu)) {
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printk(KERN_INFO "kexec: Waking offline cpu %d.\n",
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cpu);
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WARN_ON(cpu_up(cpu));
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}
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}
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}
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static void kexec_prepare_cpus(void)
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{
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wake_offline_cpus();
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smp_call_function(kexec_smp_down, NULL, /* wait */0);
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local_irq_disable();
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hard_irq_disable();
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mb(); /* make sure IRQs are disabled before we say they are */
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get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;
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kexec_prepare_cpus_wait(KEXEC_STATE_IRQS_OFF);
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/* we are sure every CPU has IRQs off at this point */
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kexec_all_irq_disabled = 1;
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/* after we tell the others to go down */
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if (ppc_md.kexec_cpu_down)
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ppc_md.kexec_cpu_down(0, 0);
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/*
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* Before removing MMU mappings make sure all CPUs have entered real
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* mode:
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*/
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kexec_prepare_cpus_wait(KEXEC_STATE_REAL_MODE);
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put_cpu();
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}
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#else /* ! SMP */
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static void kexec_prepare_cpus(void)
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{
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/*
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* move the secondarys to us so that we can copy
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* the new kernel 0-0x100 safely
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*
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* do this if kexec in setup.c ?
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*
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* We need to release the cpus if we are ever going from an
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* UP to an SMP kernel.
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*/
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smp_release_cpus();
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if (ppc_md.kexec_cpu_down)
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ppc_md.kexec_cpu_down(0, 0);
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local_irq_disable();
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hard_irq_disable();
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}
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#endif /* SMP */
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/*
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* kexec thread structure and stack.
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*
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* We need to make sure that this is 16384-byte aligned due to the
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* way process stacks are handled. It also must be statically allocated
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* or allocated as part of the kimage, because everything else may be
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* overwritten when we copy the kexec image. We piggyback on the
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* "init_task" linker section here to statically allocate a stack.
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*
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* We could use a smaller stack if we don't care about anything using
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* current, but that audit has not been performed.
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*/
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static union thread_union kexec_stack __init_task_data =
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{ };
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/*
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* For similar reasons to the stack above, the kexecing CPU needs to be on a
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* static PACA; we switch to kexec_paca.
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*/
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struct paca_struct kexec_paca;
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/* Our assembly helper, in misc_64.S */
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extern void kexec_sequence(void *newstack, unsigned long start,
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void *image, void *control,
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void (*clear_all)(void)) __noreturn;
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/* too late to fail here */
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void default_machine_kexec(struct kimage *image)
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{
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/* prepare control code if any */
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/*
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* If the kexec boot is the normal one, need to shutdown other cpus
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* into our wait loop and quiesce interrupts.
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* Otherwise, in the case of crashed mode (crashing_cpu >= 0),
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* stopping other CPUs and collecting their pt_regs is done before
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* using debugger IPI.
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*/
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if (crashing_cpu == -1)
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kexec_prepare_cpus();
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pr_debug("kexec: Starting switchover sequence.\n");
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/* switch to a staticly allocated stack. Based on irq stack code.
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* We setup preempt_count to avoid using VMX in memcpy.
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* XXX: the task struct will likely be invalid once we do the copy!
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*/
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kexec_stack.thread_info.task = current_thread_info()->task;
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kexec_stack.thread_info.flags = 0;
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kexec_stack.thread_info.preempt_count = HARDIRQ_OFFSET;
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kexec_stack.thread_info.cpu = current_thread_info()->cpu;
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/* We need a static PACA, too; copy this CPU's PACA over and switch to
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* it. Also poison per_cpu_offset to catch anyone using non-static
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* data.
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*/
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memcpy(&kexec_paca, get_paca(), sizeof(struct paca_struct));
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kexec_paca.data_offset = 0xedeaddeadeeeeeeeUL;
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paca = (struct paca_struct *)RELOC_HIDE(&kexec_paca, 0) -
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kexec_paca.paca_index;
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setup_paca(&kexec_paca);
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/* XXX: If anyone does 'dynamic lppacas' this will also need to be
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* switched to a static version!
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*/
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/* Some things are best done in assembly. Finding globals with
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* a toc is easier in C, so pass in what we can.
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*/
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kexec_sequence(&kexec_stack, image->start, image,
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page_address(image->control_code_page),
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ppc_md.hpte_clear_all);
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/* NOTREACHED */
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}
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/* Values we need to export to the second kernel via the device tree. */
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static unsigned long htab_base;
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static unsigned long htab_size;
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static struct property htab_base_prop = {
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.name = "linux,htab-base",
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.length = sizeof(unsigned long),
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.value = &htab_base,
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};
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static struct property htab_size_prop = {
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.name = "linux,htab-size",
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.length = sizeof(unsigned long),
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.value = &htab_size,
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};
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static int __init export_htab_values(void)
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{
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struct device_node *node;
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struct property *prop;
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/* On machines with no htab htab_address is NULL */
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if (!htab_address)
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return -ENODEV;
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node = of_find_node_by_path("/chosen");
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if (!node)
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return -ENODEV;
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/* remove any stale propertys so ours can be found */
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prop = of_find_property(node, htab_base_prop.name, NULL);
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if (prop)
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of_remove_property(node, prop);
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prop = of_find_property(node, htab_size_prop.name, NULL);
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if (prop)
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of_remove_property(node, prop);
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htab_base = cpu_to_be64(__pa(htab_address));
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of_add_property(node, &htab_base_prop);
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htab_size = cpu_to_be64(htab_size_bytes);
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of_add_property(node, &htab_size_prop);
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of_node_put(node);
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return 0;
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}
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late_initcall(export_htab_values);
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