From: Daniel Thompson <daniel.thompson@linaro.org>
To: Thomas Gleixner <tglx@linutronix.de>,
Jason Cooper <jason@lakedaemon.net>
Cc: Daniel Thompson <daniel.thompson@linaro.org>,
Russell King <linux@arm.linux.org.uk>,
Will Deacon <will.deacon@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Marc Zyngier <marc.zyngier@arm.com>,
Stephen Boyd <sboyd@codeaurora.org>,
John Stultz <john.stultz@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, patches@linaro.org,
linaro-kernel@lists.linaro.org,
Sumit Semwal <sumit.semwal@linaro.org>,
Dirk Behme <dirk.behme@de.bosch.com>,
Daniel Drake <drake@endlessm.com>,
Dmitry Pervushin <dpervushin@gmail.com>,
Tim Sander <tim@krieglstein.org>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org
Subject: [PATCH 4.0-rc5 v19 5/6] x86/nmi: Use common printk functions
Date: Tue, 24 Mar 2015 16:53:33 +0000 [thread overview]
Message-ID: <1427216014-5324-6-git-send-email-daniel.thompson@linaro.org> (raw)
In-Reply-To: <1427216014-5324-1-git-send-email-daniel.thompson@linaro.org>
Much of the code sitting in arch/x86/kernel/apic/hw_nmi.c to support safe
all-cpu backtracing from NMI has been copied to printk.c to make it
accessible to other architectures.
Port the x86 NMI backtrace to the generic code.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
---
arch/x86/Kconfig | 1 +
arch/x86/kernel/apic/hw_nmi.c | 101 +++---------------------------------------
2 files changed, 8 insertions(+), 94 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b7d31ca55187..a1a54570f2d0 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -141,6 +141,7 @@ config X86
select ACPI_LEGACY_TABLES_LOOKUP if ACPI
select X86_FEATURE_NAMES if PROC_FS
select SRCU
+ select PRINTK_NMI_BACKTRACE if X86_LOCAL_APIC
config INSTRUCTION_DECODER
def_bool y
diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index 6873ab925d00..db934f9461ed 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -30,40 +30,16 @@ u64 hw_nmi_get_sample_period(int watchdog_thresh)
#ifdef arch_trigger_all_cpu_backtrace
/* For reliability, we're prepared to waste bits here. */
static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
-static cpumask_t printtrace_mask;
-
-#define NMI_BUF_SIZE 4096
-
-struct nmi_seq_buf {
- unsigned char buffer[NMI_BUF_SIZE];
- struct seq_buf seq;
-};
-
-/* Safe printing in NMI context */
-static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq);
-
-/* "in progress" flag of arch_trigger_all_cpu_backtrace */
-static unsigned long backtrace_flag;
-
-static void print_seq_line(struct nmi_seq_buf *s, int start, int end)
-{
- const char *buf = s->buffer + start;
-
- printk("%.*s", (end - start) + 1, buf);
-}
void arch_trigger_all_cpu_backtrace(bool include_self)
{
- struct nmi_seq_buf *s;
- int len;
- int cpu;
int i;
int this_cpu = get_cpu();
- if (test_and_set_bit(0, &backtrace_flag)) {
+ if (0 != printk_nmi_backtrace_prepare()) {
/*
- * If there is already a trigger_all_cpu_backtrace() in progress
- * (backtrace_flag == 1), don't output double cpu dump infos.
+ * If there is already an nmi printk sequence in
+ * progress then just give up...
*/
put_cpu();
return;
@@ -73,16 +49,6 @@ void arch_trigger_all_cpu_backtrace(bool include_self)
if (!include_self)
cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
- cpumask_copy(&printtrace_mask, to_cpumask(backtrace_mask));
- /*
- * Set up per_cpu seq_buf buffers that the NMIs running on the other
- * CPUs will write to.
- */
- for_each_cpu(cpu, to_cpumask(backtrace_mask)) {
- s = &per_cpu(nmi_print_seq, cpu);
- seq_buf_init(&s->seq, s->buffer, NMI_BUF_SIZE);
- }
-
if (!cpumask_empty(to_cpumask(backtrace_mask))) {
pr_info("sending NMI to %s CPUs:\n",
(include_self ? "all" : "other"));
@@ -97,73 +63,20 @@ void arch_trigger_all_cpu_backtrace(bool include_self)
touch_softlockup_watchdog();
}
- /*
- * Now that all the NMIs have triggered, we can dump out their
- * back traces safely to the console.
- */
- for_each_cpu(cpu, &printtrace_mask) {
- int last_i = 0;
-
- s = &per_cpu(nmi_print_seq, cpu);
- len = seq_buf_used(&s->seq);
- if (!len)
- continue;
-
- /* Print line by line. */
- for (i = 0; i < len; i++) {
- if (s->buffer[i] == '\n') {
- print_seq_line(s, last_i, i);
- last_i = i + 1;
- }
- }
- /* Check if there was a partial line. */
- if (last_i < len) {
- print_seq_line(s, last_i, len - 1);
- pr_cont("\n");
- }
- }
-
- clear_bit(0, &backtrace_flag);
- smp_mb__after_atomic();
+ printk_nmi_backtrace_complete();
put_cpu();
}
-/*
- * It is not safe to call printk() directly from NMI handlers.
- * It may be fine if the NMI detected a lock up and we have no choice
- * but to do so, but doing a NMI on all other CPUs to get a back trace
- * can be done with a sysrq-l. We don't want that to lock up, which
- * can happen if the NMI interrupts a printk in progress.
- *
- * Instead, we redirect the vprintk() to this nmi_vprintk() that writes
- * the content into a per cpu seq_buf buffer. Then when the NMIs are
- * all done, we can safely dump the contents of the seq_buf to a printk()
- * from a non NMI context.
- */
-static int nmi_vprintk(const char *fmt, va_list args)
-{
- struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
- unsigned int len = seq_buf_used(&s->seq);
-
- seq_buf_vprintf(&s->seq, fmt, args);
- return seq_buf_used(&s->seq) - len;
-}
-
static int
arch_trigger_all_cpu_backtrace_handler(unsigned int cmd, struct pt_regs *regs)
{
- int cpu;
-
- cpu = smp_processor_id();
+ int cpu = smp_processor_id();
if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
- printk_func_t printk_func_save = this_cpu_read(printk_func);
-
- /* Replace printk to write into the NMI seq */
- this_cpu_write(printk_func, nmi_vprintk);
+ printk_nmi_backtrace_this_cpu_begin();
printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
show_regs(regs);
- this_cpu_write(printk_func, printk_func_save);
+ printk_nmi_backtrace_this_cpu_end();
cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
return NMI_HANDLED;
--
2.1.0
next prev parent reply other threads:[~2015-03-24 16:54 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-24 16:53 [PATCH 4.0-rc5 v19 0/6] irq/arm: Implement arch_trigger_all_cpu_backtrace Daniel Thompson
2015-03-24 16:53 ` [PATCH 4.0-rc5 v19 1/6] irqchip: gic: Optimize locking in gic_raise_softirq Daniel Thompson
2015-03-24 16:53 ` [PATCH 4.0-rc5 v19 2/6] irqchip: gic: Make gic_raise_softirq FIQ-safe Daniel Thompson
2015-03-24 16:53 ` [PATCH 4.0-rc5 v19 3/6] irqchip: gic: Introduce plumbing for IPI FIQ Daniel Thompson
2015-03-24 16:53 ` [PATCH 4.0-rc5 v19 4/6] printk: Simple implementation for NMI backtracing Daniel Thompson
2015-03-24 16:53 ` Daniel Thompson [this message]
2015-03-24 16:53 ` [PATCH 4.0-rc5 v19 6/6] ARM: Add support for on-demand backtrace of other CPUs Daniel Thompson
2015-04-07 15:37 ` [RESEND PATCH 4.0-rc5 v19 0/6] irq/arm: Implement arch_trigger_all_cpu_backtrace Daniel Thompson
2015-04-07 15:37 ` [RESEND PATCH 4.0-rc5 v19 1/6] irqchip: gic: Optimize locking in gic_raise_softirq Daniel Thompson
2015-04-07 15:37 ` [RESEND PATCH 4.0-rc5 v19 2/6] irqchip: gic: Make gic_raise_softirq FIQ-safe Daniel Thompson
2015-04-07 15:38 ` [RESEND PATCH 4.0-rc5 v19 3/6] irqchip: gic: Introduce plumbing for IPI FIQ Daniel Thompson
2015-04-07 15:38 ` [RESEND PATCH 4.0-rc5 v19 4/6] printk: Simple implementation for NMI backtracing Daniel Thompson
2015-04-07 15:38 ` [RESEND PATCH 4.0-rc5 v19 5/6] x86/nmi: Use common printk functions Daniel Thompson
2015-04-07 16:19 ` Steven Rostedt
2015-04-07 16:37 ` Borislav Petkov
2015-04-07 16:43 ` Steven Rostedt
2015-04-08 12:08 ` Daniel Thompson
2015-04-07 15:38 ` [RESEND PATCH 4.0-rc5 v19 6/6] ARM: Add support for on-demand backtrace of other CPUs Daniel Thompson
2015-04-10 9:51 ` [RESEND PATCH 4.0-rc7 v20 0/6] irq/arm: Implement arch_trigger_all_cpu_backtrace Daniel Thompson
2015-04-10 9:51 ` [RESEND PATCH 4.0-rc7 v20 1/6] irqchip: gic: Optimize locking in gic_raise_softirq Daniel Thompson
2015-04-21 12:51 ` Marc Zyngier
2015-04-10 9:51 ` [RESEND PATCH 4.0-rc7 v20 2/6] irqchip: gic: Make gic_raise_softirq FIQ-safe Daniel Thompson
2015-04-21 12:54 ` Marc Zyngier
2015-04-10 9:51 ` [RESEND PATCH 4.0-rc7 v20 3/6] irqchip: gic: Introduce plumbing for IPI FIQ Daniel Thompson
2015-04-21 13:45 ` Marc Zyngier
2015-04-21 21:03 ` Daniel Thompson
2015-04-22 9:15 ` Marc Zyngier
2015-04-22 12:45 ` Daniel Thompson
2015-04-22 12:57 ` Marc Zyngier
2015-04-22 15:40 ` Daniel Thompson
2015-04-21 14:50 ` Mark Rutland
2015-04-21 21:15 ` Daniel Thompson
2015-04-22 10:38 ` Mark Rutland
2015-07-02 13:31 ` Daniel Thompson
2015-04-10 9:51 ` [RESEND PATCH 4.0-rc7 v20 4/6] printk: Simple implementation for NMI backtracing Daniel Thompson
2015-04-10 9:51 ` [RESEND PATCH 4.0-rc7 v20 5/6] x86/nmi: Use common printk functions Daniel Thompson
2015-04-10 9:51 ` [RESEND PATCH 4.0-rc7 v20 6/6] ARM: Add support for on-demand backtrace of other CPUs Daniel Thompson
2015-04-10 10:47 ` [RESEND PATCH 4.0-rc7 v20 0/6] irq/arm: Implement arch_trigger_all_cpu_backtrace Daniel Thompson
2015-04-21 12:46 ` Thomas Gleixner
2015-04-21 13:08 ` Marc Zyngier
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