Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1384122 > unrolled thread
| Started by | Petr Mladek <pmladek@suse.com> |
|---|---|
| First post | 2016-04-21 13:50 +0200 |
| Last post | 2016-04-27 02:40 +0200 |
| Articles | 3 — 2 participants |
Back to article view | Back to linux.kernel
[PATCH v5 0/4] Cleaning printk stuff in NMI context Petr Mladek <pmladek@suse.com> - 2016-04-21 13:50 +0200
[PATCH v5 3/4] printk/nmi: increase the size of NMI buffer and make it configurable Petr Mladek <pmladek@suse.com> - 2016-04-21 14:00 +0200
Re: [PATCH v5 0/4] Cleaning printk stuff in NMI context Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-04-27 02:40 +0200
| From | Petr Mladek <pmladek@suse.com> |
|---|---|
| Date | 2016-04-21 13:50 +0200 |
| Subject | [PATCH v5 0/4] Cleaning printk stuff in NMI context |
| Message-ID | <rqlhn-8vU-5@gated-at.bofh.it> |
This patch set generalizes the already existing solution for
printing NMI messages. The main idea comes from Peter Zijlstra.
v5 adds changes suggested by Sergey Senozhatsky. It should not longer
conflict with his async printk patchset.
There are some conflicts with the nmi_backtrace improvements
from Chris Metcalf, see
https://lkml.kernel.org/g/<1459877208-15119-1-git-send-email-cmetcalf@mellanox.com>
Feel free to ask me to resolve them.
Changes against v4:
+ merged 2nd patch into the 1st one to do not break bisection
+ set vprintk_nmi() early in nmi_enter() and set vprintk_default()
later in nmi_exit() to make sure that all NMI messages are printed
to the temporary ring buffer
+ used printk_deferred() when flushing the temporary buffers
on panic in NMI; we do not longer need to touch vprintk_emit()
and define the ugly macro deferred_console_in_nmi().
Changes against v3:
+ merged all small changes from -mm tree, including commit
descriptions
+ disabled interrupts when taking the read_lock in __printk_nmi_flush();
printk_nmi_flush() might be called from any context; reported
by lockdep
+ never introduce NEED_PRINTK_NMI; in -mm tree was introduced
in 1st patch and removed in the 4th one
+ flush NMI buffers when the system goes down (new 5th patch);
addresses Daniel's concerns
Changes against v2:
+ fixed compilation problems reported by 0-day build robot
+ MN10300 and Xtensa architectures will get handled separately
+ dropped the patch that printed NMI messages directly when Oops
in progress; it made the solution less reliable
+ made the size of the buffer configurable; use real numbers
instead of PAGE_SIZE
Changes against v1:
+ rebased on top of 4.4-rc2; there the old implementation was
moved to lib/nmi_backtrace.c and used also on arm; I hope that
I got the arm side correctly; I was not able to test on arm :-(
+ defined HAVE_NMI on arm for !CPU_V7M instead of !CPU_V7;
handle_fiq_as_nmi() is called from entry-armv.S that
is compiled when !CPU_V7M
+ defined HAVE_NMI also on mips; it calls nmi_enter() and
seems to have real NMIs (or am I wrong?)
+ serialized backtraces when printing directly
(oops_in_progress)
Petr Mladek (4):
printk/nmi: generic solution for safe printk in NMI
printk/nmi: warn when some message has been lost in NMI context
printk/nmi: increase the size of NMI buffer and make it configurable
printk/nmi: flush NMI messages on the system panic
arch/Kconfig | 4 +
arch/arm/Kconfig | 1 +
arch/arm/kernel/smp.c | 2 +
arch/avr32/Kconfig | 1 +
arch/blackfin/Kconfig | 1 +
arch/cris/Kconfig | 1 +
arch/mips/Kconfig | 1 +
arch/powerpc/Kconfig | 1 +
arch/s390/Kconfig | 1 +
arch/sh/Kconfig | 1 +
arch/sparc/Kconfig | 1 +
arch/tile/Kconfig | 1 +
arch/x86/Kconfig | 1 +
arch/x86/kernel/apic/hw_nmi.c | 1 -
include/linux/hardirq.h | 2 +
include/linux/percpu.h | 3 -
include/linux/printk.h | 14 ++-
init/Kconfig | 27 +++++
init/main.c | 1 +
kernel/kexec_core.c | 1 +
kernel/panic.c | 6 +-
kernel/printk/Makefile | 1 +
kernel/printk/internal.h | 57 +++++++++
kernel/printk/nmi.c | 260 ++++++++++++++++++++++++++++++++++++++++++
kernel/printk/printk.c | 31 ++---
lib/nmi_backtrace.c | 89 +--------------
26 files changed, 401 insertions(+), 109 deletions(-)
create mode 100644 kernel/printk/internal.h
create mode 100644 kernel/printk/nmi.c
--
1.8.5.6
[toc] | [next] | [standalone]
| From | Petr Mladek <pmladek@suse.com> |
|---|---|
| Date | 2016-04-21 14:00 +0200 |
| Subject | [PATCH v5 3/4] printk/nmi: increase the size of NMI buffer and make it configurable |
| Message-ID | <rqlr4-8y-3@gated-at.bofh.it> |
| In reply to | #1384122 |
Testing has shown that the backtrace sometimes does not fit into the 4kB
temporary buffer that is used in NMI context. The warnings are gone when
I double the temporary buffer size.
This patch doubles the buffer size and makes it configurable.
Note that this problem existed even in the x86-specific implementation
that was added by the commit a9edc8809328 ("x86/nmi: Perform a safe NMI
stack trace on all CPUs"). Nobody noticed it because it did not print any
warnings.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
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>
---
init/Kconfig | 22 ++++++++++++++++++++++
kernel/printk/nmi.c | 3 ++-
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/init/Kconfig b/init/Kconfig
index 85c7a2bf1ea4..9dfd27394d43 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -862,6 +862,28 @@ config LOG_CPU_MAX_BUF_SHIFT
13 => 8 KB for each CPU
12 => 4 KB for each CPU
+config NMI_LOG_BUF_SHIFT
+ int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)"
+ range 10 21
+ default 13
+ depends on PRINTK_NMI
+ help
+ Select the size of a per-CPU buffer where NMI messages are temporary
+ stored. They are copied to the main log buffer in a safe context
+ to avoid a deadlock. The value defines the size as a power of 2.
+
+ NMI messages are rare and limited. The largest one is when
+ a backtrace is printed. It usually fits into 4KB. Select
+ 8KB if you want to be on the safe side.
+
+ Examples:
+ 17 => 128 KB for each CPU
+ 16 => 64 KB for each CPU
+ 15 => 32 KB for each CPU
+ 14 => 16 KB for each CPU
+ 13 => 8 KB for each CPU
+ 12 => 4 KB for each CPU
+
#
# Architectures with an unreliable sched_clock() should select this:
#
diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c
index 572f94922230..bf08557d7e3d 100644
--- a/kernel/printk/nmi.c
+++ b/kernel/printk/nmi.c
@@ -41,7 +41,8 @@ DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
static int printk_nmi_irq_ready;
atomic_t nmi_message_lost;
-#define NMI_LOG_BUF_LEN (4096 - sizeof(atomic_t) - sizeof(struct irq_work))
+#define NMI_LOG_BUF_LEN ((1 << CONFIG_NMI_LOG_BUF_SHIFT) - \
+ sizeof(atomic_t) - sizeof(struct irq_work))
struct nmi_seq_buf {
atomic_t len; /* length of written data */
--
1.8.5.6
[toc] | [prev] | [next] | [standalone]
| From | Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> |
|---|---|
| Date | 2016-04-27 02:40 +0200 |
| Message-ID | <rslGk-kK-53@gated-at.bofh.it> |
| In reply to | #1384122 |
On (04/21/16 13:48), Petr Mladek wrote: > v5 adds changes suggested by Sergey Senozhatsky. It should not longer > conflict with his async printk patchset. passes my tests. (apart from that cosmetic-nano-nit) the series looks good to me Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> -ss
[toc] | [prev] | [standalone]
Back to top | Article view | linux.kernel
csiph-web