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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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a9ca8eb7af
With git commit 4d92f50249 ("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>
104 lines
2.3 KiB
C
104 lines
2.3 KiB
C
/*
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* Copyright IBM Corp. 2008
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* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
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*/
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#define KMSG_COMPONENT "cpu"
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#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/seq_file.h>
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#include <linux/delay.h>
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#include <linux/cpu.h>
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#include <asm/elf.h>
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#include <asm/lowcore.h>
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#include <asm/param.h>
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#include <asm/smp.h>
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static DEFINE_PER_CPU(struct cpuid, cpu_id);
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void notrace cpu_relax(void)
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{
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if (!smp_cpu_mtid && MACHINE_HAS_DIAG44)
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asm volatile("diag 0,0,0x44");
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barrier();
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}
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EXPORT_SYMBOL(cpu_relax);
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/*
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* cpu_init - initializes state that is per-CPU.
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*/
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void cpu_init(void)
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{
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struct cpuid *id = this_cpu_ptr(&cpu_id);
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get_cpu_id(id);
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atomic_inc(&init_mm.mm_count);
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current->active_mm = &init_mm;
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BUG_ON(current->mm);
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enter_lazy_tlb(&init_mm, current);
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}
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/*
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* show_cpuinfo - Get information on one CPU for use by procfs.
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*/
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static int show_cpuinfo(struct seq_file *m, void *v)
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{
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static const char *hwcap_str[] = {
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"esan3", "zarch", "stfle", "msa", "ldisp", "eimm", "dfp",
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"edat", "etf3eh", "highgprs", "te", "vx"
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};
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unsigned long n = (unsigned long) v - 1;
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int i;
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if (!n) {
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s390_adjust_jiffies();
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seq_printf(m, "vendor_id : IBM/S390\n"
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"# processors : %i\n"
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"bogomips per cpu: %lu.%02lu\n",
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num_online_cpus(), loops_per_jiffy/(500000/HZ),
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(loops_per_jiffy/(5000/HZ))%100);
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seq_puts(m, "features\t: ");
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for (i = 0; i < ARRAY_SIZE(hwcap_str); i++)
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if (hwcap_str[i] && (elf_hwcap & (1UL << i)))
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seq_printf(m, "%s ", hwcap_str[i]);
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seq_puts(m, "\n");
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show_cacheinfo(m);
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}
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get_online_cpus();
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if (cpu_online(n)) {
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struct cpuid *id = &per_cpu(cpu_id, n);
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seq_printf(m, "processor %li: "
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"version = %02X, "
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"identification = %06X, "
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"machine = %04X\n",
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n, id->version, id->ident, id->machine);
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}
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put_online_cpus();
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return 0;
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}
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static void *c_start(struct seq_file *m, loff_t *pos)
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{
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return *pos < nr_cpu_ids ? (void *)((unsigned long) *pos + 1) : NULL;
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}
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static void *c_next(struct seq_file *m, void *v, loff_t *pos)
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{
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++*pos;
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return c_start(m, pos);
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}
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static void c_stop(struct seq_file *m, void *v)
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{
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}
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const struct seq_operations cpuinfo_op = {
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.start = c_start,
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.next = c_next,
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.stop = c_stop,
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.show = show_cpuinfo,
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};
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