From 088e9d253d3a4ab7e058dd84bb532c32dadf1882 Mon Sep 17 00:00:00 2001 From: Daniel Bristot de Oliveira Date: Thu, 2 Jun 2016 13:51:41 -0300 Subject: rcu: sysctl: Panic on RCU Stall It is not always easy to determine the cause of an RCU stall just by analysing the RCU stall messages, mainly when the problem is caused by the indirect starvation of rcu threads. For example, when preempt_rcu is not awakened due to the starvation of a timer softirq. We have been hard coding panic() in the RCU stall functions for some time while testing the kernel-rt. But this is not possible in some scenarios, like when supporting customers. This patch implements the sysctl kernel.panic_on_rcu_stall. If set to 1, the system will panic() when an RCU stall takes place, enabling the capture of a vmcore. The vmcore provides a way to analyze all kernel/tasks states, helping out to point to the culprit and the solution for the stall. The kernel.panic_on_rcu_stall sysctl is disabled by default. Changes from v1: - Fixed a typo in the git log - The if(sysctl_panic_on_rcu_stall) panic() is in a static function - Fixed the CONFIG_TINY_RCU compilation issue - The var sysctl_panic_on_rcu_stall is now __read_mostly Cc: Jonathan Corbet Cc: "Paul E. McKenney" Cc: Josh Triplett Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: Lai Jiangshan Acked-by: Christian Borntraeger Reviewed-by: Josh Triplett Reviewed-by: Arnaldo Carvalho de Melo Tested-by: "Luis Claudio R. Goncalves" Signed-off-by: Daniel Bristot de Oliveira Signed-off-by: Paul E. McKenney --- include/linux/kernel.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 94aa10ffe156..c42082112ec8 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -451,6 +451,7 @@ extern int panic_on_oops; extern int panic_on_unrecovered_nmi; extern int panic_on_io_nmi; extern int panic_on_warn; +extern int sysctl_panic_on_rcu_stall; extern int sysctl_panic_on_stackoverflow; extern bool crash_kexec_post_notifiers; -- cgit v1.2.3 From 9d5059c959ac739dbf837cec14586e58e7a67292 Mon Sep 17 00:00:00 2001 From: Luis de Bethencourt Date: Tue, 2 Aug 2016 14:03:47 -0700 Subject: dynamic_debug: only add header when used kernel.h header doesn't directly use dynamic debug, instead we can include it in module.c (which used it via kernel.h). printk.h only uses it if CONFIG_DYNAMIC_DEBUG is on, changing the inclusion to only happen in that case. Link: http://lkml.kernel.org/r/1468429793-16917-1-git-send-email-luisbg@osg.samsung.com [luisbg@osg.samsung.com: include dynamic_debug.h in drb_int.h] Link: http://lkml.kernel.org/r/1468447828-18558-2-git-send-email-luisbg@osg.samsung.com Signed-off-by: Luis de Bethencourt Cc: Rusty Russell Cc: Hidehiro Kawai Cc: Borislav Petkov Cc: Michal Nazarewicz Cc: Rasmus Villemoes Cc: Joe Perches Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/block/drbd/drbd_actlog.c | 1 - drivers/block/drbd/drbd_int.h | 1 + include/linux/kernel.h | 1 - include/linux/printk.h | 3 ++- kernel/module.c | 1 + 5 files changed, 4 insertions(+), 3 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c index 0a1aaf8c24c4..2d3d50ab74bf 100644 --- a/drivers/block/drbd/drbd_actlog.c +++ b/drivers/block/drbd/drbd_actlog.c @@ -27,7 +27,6 @@ #include #include #include -#include #include "drbd_int.h" diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h index 7b54354976a5..4cb8f21ff4ef 100644 --- a/drivers/block/drbd/drbd_int.h +++ b/drivers/block/drbd/drbd_int.h @@ -41,6 +41,7 @@ #include #include #include +#include #include #include #include diff --git a/include/linux/kernel.h b/include/linux/kernel.h index c42082112ec8..d96a6118d26a 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -11,7 +11,6 @@ #include #include #include -#include #include #include diff --git a/include/linux/printk.h b/include/linux/printk.h index f136b22c7772..987c65ed34e5 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -289,10 +289,11 @@ extern asmlinkage void dump_stack(void) __cold; no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) #endif -#include /* If you are writing a driver, please use dev_dbg instead */ #if defined(CONFIG_DYNAMIC_DEBUG) +#include + /* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */ #define pr_debug(fmt, ...) \ dynamic_pr_debug(fmt, ##__VA_ARGS__) diff --git a/kernel/module.c b/kernel/module.c index 5f71aa63ed2a..a0f48b8b00da 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -60,6 +60,7 @@ #include #include #include +#include #include #include "module-internal.h" -- cgit v1.2.3