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authorPetr Mladek <pmladek@suse.com>2021-07-27 10:09:39 +0200
committerPetr Mladek <pmladek@suse.com>2021-07-30 09:25:34 +0200
commit26d1982fd17c2cac77f9cf764255362ccb28fe49 (patch)
tree161675bef5e0c060a0962fca2abbb712e5f40a69 /lib
parent8d909b2333f37e5da84a9e6a2cbe21f52be5f42a (diff)
lib/nmi_backtrace: Serialize even messages about idle CPUs
The commit 55d6af1d66885059ffc2a ("lib/nmi_backtrace: explicitly serialize banner and regs") serialized backtraces from more CPUs using the re-entrant printk_printk_cpu lock. It was a preparation step for removing the obsolete nmi_safe buffers. The single-line messages about idle CPUs were not serialized against other CPUs and might appear in the middle of backtrace from another CPU, for example: [56394.590068] NMI backtrace for cpu 2 [56394.590069] CPU: 2 PID: 444 Comm: systemd-journal Not tainted 5.14.0-rc1-default+ #268 [56394.590071] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014 [56394.590072] RIP: 0010:lock_is_held_type+0x0/0x120 [56394.590071] NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0xb/0x10 [56394.590076] Code: a2 38 ff 0f 0b 8b 44 24 04 eb bd 48 8d ... [56394.590077] RSP: 0018:ffffab02c07c7e68 EFLAGS: 00000246 [56394.590079] RAX: 0000000000000000 RBX: ffff9a7bc0ec8a40 RCX: ffffffffaab8eb40 It might cause confusion what CPU the following lines belongs to and whether the backtraces are really serialized. Prevent the confusion and serialize also the single line message against other CPUs. Fixes: 55d6af1d66885059ffc2a ("lib/nmi_backtrace: explicitly serialize banner and regs") Reviewed-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20210727080939.27193-1-pmladek@suse.com
Diffstat (limited to 'lib')
-rw-r--r--lib/nmi_backtrace.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index 9813a983d024..f9e89001b52e 100644
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -89,22 +89,22 @@ bool nmi_cpu_backtrace(struct pt_regs *regs)
unsigned long flags;
if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
+ /*
+ * Allow nested NMI backtraces while serializing
+ * against other CPUs.
+ */
+ printk_cpu_lock_irqsave(flags);
if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {
pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
cpu, (void *)instruction_pointer(regs));
} else {
- /*
- * Allow nested NMI backtraces while serializing
- * against other CPUs.
- */
- printk_cpu_lock_irqsave(flags);
pr_warn("NMI backtrace for cpu %d\n", cpu);
if (regs)
show_regs(regs);
else
dump_stack();
- printk_cpu_unlock_irqrestore(flags);
}
+ printk_cpu_unlock_irqrestore(flags);
cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
return true;
}