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authorPetr Mladek <pmladek@suse.com>2016-05-20 17:00:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-20 17:58:30 -0700
commit42a0bb3f71383b457a7db362f1c69e7afb96732b (patch)
treec63f12bed74fee20662fbcc8cc985d53a0d20def /arch
parent2eeed7e98d6a1341b1574893a95ce5b8379140f2 (diff)
downloadlinux-42a0bb3f71383b457a7db362f1c69e7afb96732b.tar.gz
printk/nmi: generic solution for safe printk in NMI
printk() takes some locks and could not be used a safe way in NMI context. The chance of a deadlock is real especially when printing stacks from all CPUs. This particular problem has been addressed on x86 by the commit a9edc8809328 ("x86/nmi: Perform a safe NMI stack trace on all CPUs"). The patchset brings two big advantages. First, it makes the NMI backtraces safe on all architectures for free. Second, it makes all NMI messages almost safe on all architectures (the temporary buffer is limited. We still should keep the number of messages in NMI context at minimum). Note that there already are several messages printed in NMI context: WARN_ON(in_nmi()), BUG_ON(in_nmi()), anything being printed out from MCE handlers. These are not easy to avoid. This patch reuses most of the code and makes it generic. It is useful for all messages and architectures that support NMI. The alternative printk_func is set when entering and is reseted when leaving NMI context. It queues IRQ work to copy the messages into the main ring buffer in a safe context. __printk_nmi_flush() copies all available messages and reset the buffer. Then we could use a simple cmpxchg operations to get synchronized with writers. There is also used a spinlock to get synchronized with other flushers. We do not longer use seq_buf because it depends on external lock. It would be hard to make all supported operations safe for a lockless use. It would be confusing and error prone to make only some operations safe. The code is put into separate printk/nmi.c as suggested by Steven Rostedt. It needs a per-CPU buffer and is compiled only on architectures that call nmi_enter(). This is achieved by the new HAVE_NMI Kconfig flag. The are MN10300 and Xtensa architectures. We need to clean up NMI handling there first. Let's do it separately. The patch is heavily based on the draft from Peter Zijlstra, see https://lkml.org/lkml/2015/6/10/327 [arnd@arndb.de: printk-nmi: use %zu format string for size_t] [akpm@linux-foundation.org: min_t->min - all types are size_t here] Signed-off-by: Petr Mladek <pmladek@suse.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Cc: Jan Kara <jack@suse.cz> Acked-by: Russell King <rmk+kernel@arm.linux.org.uk> [arm part] Cc: Daniel Thompson <daniel.thompson@linaro.org> Cc: Jiri Kosina <jkosina@suse.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: David Miller <davem@davemloft.net> Cc: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/Kconfig4
-rw-r--r--arch/arm/Kconfig1
-rw-r--r--arch/arm/kernel/smp.c2
-rw-r--r--arch/avr32/Kconfig1
-rw-r--r--arch/blackfin/Kconfig1
-rw-r--r--arch/cris/Kconfig1
-rw-r--r--arch/mips/Kconfig1
-rw-r--r--arch/powerpc/Kconfig1
-rw-r--r--arch/s390/Kconfig1
-rw-r--r--arch/sh/Kconfig1
-rw-r--r--arch/sparc/Kconfig1
-rw-r--r--arch/tile/Kconfig1
-rw-r--r--arch/x86/Kconfig1
-rw-r--r--arch/x86/kernel/apic/hw_nmi.c1
14 files changed, 17 insertions, 1 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index 0f298f9123dc..8f84fd268dee 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -187,7 +187,11 @@ config HAVE_OPTPROBES
config HAVE_KPROBES_ON_FTRACE
bool
+config HAVE_NMI
+ bool
+
config HAVE_NMI_WATCHDOG
+ depends on HAVE_NMI
bool
#
# An arch should select this if it provides all these things:
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 956d3575426c..90542db1220d 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -67,6 +67,7 @@ config ARM
select HAVE_KRETPROBES if (HAVE_KPROBES)
select HAVE_MEMBLOCK
select HAVE_MOD_ARCH_SPECIFIC
+ select HAVE_NMI
select HAVE_OPROFILE if (HAVE_PERF_EVENTS)
select HAVE_OPTPROBES if !THUMB2_KERNEL
select HAVE_PERF_EVENTS
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index baee70267f29..df90bc59bfce 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -644,9 +644,11 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
break;
case IPI_CPU_BACKTRACE:
+ printk_nmi_enter();
irq_enter();
nmi_cpu_backtrace(regs);
irq_exit();
+ printk_nmi_exit();
break;
default:
diff --git a/arch/avr32/Kconfig b/arch/avr32/Kconfig
index e43519a2ca89..7e75d45e20cd 100644
--- a/arch/avr32/Kconfig
+++ b/arch/avr32/Kconfig
@@ -18,6 +18,7 @@ config AVR32
select GENERIC_CLOCKEVENTS
select HAVE_MOD_ARCH_SPECIFIC
select MODULES_USE_ELF_RELA
+ select HAVE_NMI
help
AVR32 is a high-performance 32-bit RISC microprocessor core,
designed for cost-sensitive embedded applications, with particular
diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index a63c12259e77..28c63fea786d 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -40,6 +40,7 @@ config BLACKFIN
select HAVE_MOD_ARCH_SPECIFIC
select MODULES_USE_ELF_RELA
select HAVE_DEBUG_STACKOVERFLOW
+ select HAVE_NMI
config GENERIC_CSUM
def_bool y
diff --git a/arch/cris/Kconfig b/arch/cris/Kconfig
index 5c0ca8ae9293..deba2662b9f3 100644
--- a/arch/cris/Kconfig
+++ b/arch/cris/Kconfig
@@ -70,6 +70,7 @@ config CRIS
select GENERIC_CLOCKEVENTS if ETRAX_ARCH_V32
select GENERIC_SCHED_CLOCK if ETRAX_ARCH_V32
select HAVE_DEBUG_BUGVERBOSE if ETRAX_ARCH_V32
+ select HAVE_NMI
config HZ
int
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 5663f411c225..8040fb1845b4 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -48,6 +48,7 @@ config MIPS
select GENERIC_SCHED_CLOCK if !CAVIUM_OCTEON_SOC
select GENERIC_CMOS_UPDATE
select HAVE_MOD_ARCH_SPECIFIC
+ select HAVE_NMI
select VIRT_TO_BUS
select MODULES_USE_ELF_REL if MODULES
select MODULES_USE_ELF_RELA if MODULES && 64BIT
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index f0403b58ae8b..01f7464d9fea 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -155,6 +155,7 @@ config PPC
select NO_BOOTMEM
select HAVE_GENERIC_RCU_GUP
select HAVE_PERF_EVENTS_NMI if PPC64
+ select HAVE_NMI if PERF_EVENTS
select EDAC_SUPPORT
select EDAC_ATOMIC_SCRUB
select ARCH_HAS_DMA_SET_COHERENT_MASK
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index e2c9aaaf64b2..1c3c43d9d1b5 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -166,6 +166,7 @@ config S390
select TTY
select VIRT_CPU_ACCOUNTING
select VIRT_TO_BUS
+ select HAVE_NMI
config SCHED_OMIT_FRAME_POINTER
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index cb93af8f8017..f6254341c065 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -44,6 +44,7 @@ config SUPERH
select OLD_SIGSUSPEND
select OLD_SIGACTION
select HAVE_ARCH_AUDITSYSCALL
+ select HAVE_NMI
help
The SuperH is a RISC processor targeted for use in embedded systems
and consumer electronics; it was also used in the Sega Dreamcast
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 27b3a0ad40a0..1012f7ffcdf5 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -79,6 +79,7 @@ config SPARC64
select NO_BOOTMEM
select HAVE_ARCH_AUDITSYSCALL
select ARCH_SUPPORTS_ATOMIC_RMW
+ select HAVE_NMI
config ARCH_DEFCONFIG
string
diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 174746225577..76989b878f3c 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -30,6 +30,7 @@ config TILE
select HAVE_DEBUG_STACKOVERFLOW
select ARCH_WANT_FRAME_POINTERS
select HAVE_CONTEXT_TRACKING
+ select HAVE_NMI if USE_PMC
select EDAC_SUPPORT
select GENERIC_STRNCPY_FROM_USER
select GENERIC_STRNLEN_USER
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8ff5b3be95d4..0a7b885964ba 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -131,6 +131,7 @@ config X86
select HAVE_MEMBLOCK
select HAVE_MEMBLOCK_NODE_MAP
select HAVE_MIXED_BREAKPOINTS_REGS
+ select HAVE_NMI
select HAVE_OPROFILE
select HAVE_OPTPROBES
select HAVE_PCSPKR_PLATFORM
diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index 045e424fb368..7788ce643bf4 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -18,7 +18,6 @@
#include <linux/nmi.h>
#include <linux/module.h>
#include <linux/delay.h>
-#include <linux/seq_buf.h>
#ifdef CONFIG_HARDLOCKUP_DETECTOR
u64 hw_nmi_get_sample_period(int watchdog_thresh)