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dump_stack() is called in panic(). If for some reason another CPU is holding the printk_cpu_sync and is unable to release it, the panic CPU will be unable to continue and print the stacktrace. Since non-panic CPUs are not allowed to store new printk messages anyway, there is no need to synchronize the stacktrace output in a panic situation. For the panic CPU, do not get the printk_cpu_sync because it is not needed and avoids a potential deadlock scenario in panic(). Link: https://lore.kernel.org/lkml/ZcIGKU8sxti38Kok@alley Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20240207134103.1357162-15-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com>
125 lines
3.4 KiB
C
125 lines
3.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Provide a default dump_stack() function for architectures
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* which don't implement their own.
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*/
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#include <linux/kernel.h>
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#include <linux/buildid.h>
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#include <linux/export.h>
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#include <linux/sched.h>
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#include <linux/sched/debug.h>
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#include <linux/smp.h>
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#include <linux/atomic.h>
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#include <linux/kexec.h>
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#include <linux/utsname.h>
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#include <linux/stop_machine.h>
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static char dump_stack_arch_desc_str[128];
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/**
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* dump_stack_set_arch_desc - set arch-specific str to show with task dumps
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* @fmt: printf-style format string
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* @...: arguments for the format string
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*
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* The configured string will be printed right after utsname during task
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* dumps. Usually used to add arch-specific system identifiers. If an
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* arch wants to make use of such an ID string, it should initialize this
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* as soon as possible during boot.
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*/
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void __init dump_stack_set_arch_desc(const char *fmt, ...)
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{
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va_list args;
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va_start(args, fmt);
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vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
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fmt, args);
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va_end(args);
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}
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#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
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#define BUILD_ID_FMT " %20phN"
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#define BUILD_ID_VAL vmlinux_build_id
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#else
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#define BUILD_ID_FMT "%s"
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#define BUILD_ID_VAL ""
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#endif
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/**
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* dump_stack_print_info - print generic debug info for dump_stack()
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* @log_lvl: log level
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*
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* Arch-specific dump_stack() implementations can use this function to
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* print out the same debug information as the generic dump_stack().
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*/
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void dump_stack_print_info(const char *log_lvl)
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{
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printk("%sCPU: %d PID: %d Comm: %.20s %s%s %s %.*s" BUILD_ID_FMT "\n",
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log_lvl, raw_smp_processor_id(), current->pid, current->comm,
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kexec_crash_loaded() ? "Kdump: loaded " : "",
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print_tainted(),
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init_utsname()->release,
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(int)strcspn(init_utsname()->version, " "),
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init_utsname()->version, BUILD_ID_VAL);
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if (dump_stack_arch_desc_str[0] != '\0')
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printk("%sHardware name: %s\n",
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log_lvl, dump_stack_arch_desc_str);
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print_worker_info(log_lvl, current);
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print_stop_info(log_lvl, current);
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}
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/**
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* show_regs_print_info - print generic debug info for show_regs()
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* @log_lvl: log level
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*
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* show_regs() implementations can use this function to print out generic
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* debug information.
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*/
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void show_regs_print_info(const char *log_lvl)
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{
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dump_stack_print_info(log_lvl);
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}
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static void __dump_stack(const char *log_lvl)
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{
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dump_stack_print_info(log_lvl);
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show_stack(NULL, NULL, log_lvl);
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}
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/**
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* dump_stack_lvl - dump the current task information and its stack trace
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* @log_lvl: log level
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*
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* Architectures can override this implementation by implementing its own.
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*/
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asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
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{
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bool in_panic = this_cpu_in_panic();
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unsigned long flags;
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/*
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* Permit this cpu to perform nested stack dumps while serialising
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* against other CPUs, unless this CPU is in panic.
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*
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* When in panic, non-panic CPUs are not permitted to store new
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* printk messages so there is no need to synchronize the output.
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* This avoids potential deadlock in panic() if another CPU is
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* holding and unable to release the printk_cpu_sync.
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*/
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if (!in_panic)
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printk_cpu_sync_get_irqsave(flags);
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__dump_stack(log_lvl);
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if (!in_panic)
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printk_cpu_sync_put_irqrestore(flags);
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}
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EXPORT_SYMBOL(dump_stack_lvl);
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asmlinkage __visible void dump_stack(void)
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{
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dump_stack_lvl(KERN_DEFAULT);
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}
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EXPORT_SYMBOL(dump_stack);
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