On 11/04/14 at 10:41am, Prarit Bhargava wrote: > There have been several times where I have had to rebuild a kernel to > cause a panic when hitting a WARN() in the code in order to get a crash > dump from a system. Sometimes this is easy to do, other times (such as > in the case of a remote admin) it is not trivial to send new images to the > user. > > A much easier method would be a switch to change the WARN() over to a > panic. This makes debugging easier in that I can now test the actual > image the WARN() was seen on and I do not have to engage in remote > debugging. > > This patch adds a panic_on_warn kernel parameter and > /proc/sys/kernel/panic_on_warn calls panic() in the warn_slowpath_common() > path. The function will still print out the location of the warning. > > An example of the panic_on_warn output: > > The first line below is from the WARN_ON() to output the WARN_ON()'s location. > After that the panic() output is displayed. > > WARNING: CPU: 30 PID: 11698 at /home/prarit/dummy_module/dummy-module.c:25 init_dummy+0x1f/0x30 [dummy_module]() > Kernel panic - not syncing: panic_on_warn set ... > > CPU: 30 PID: 11698 Comm: insmod Tainted: G W OE 3.17.0+ #57 > Hardware name: Intel Corporation S2600CP/S2600CP, BIOS RMLSDP.86I.00.29.D696.1311111329 11/11/2013 > 0000000000000000 000000008e3f87df ffff88080f093c38 ffffffff81665190 > 0000000000000000 ffffffff818aea3d ffff88080f093cb8 ffffffff8165e2ec > ffffffff00000008 ffff88080f093cc8 ffff88080f093c68 000000008e3f87df > Call Trace: > [<ffffffff81665190>] dump_stack+0x46/0x58 > [<ffffffff8165e2ec>] panic+0xd0/0x204 > [<ffffffffa038e05f>] ? init_dummy+0x1f/0x30 [dummy_module] > [<ffffffff81076b90>] warn_slowpath_common+0xd0/0xd0 > [<ffffffffa038e040>] ? dummy_greetings+0x40/0x40 [dummy_module] > [<ffffffff81076c8a>] warn_slowpath_null+0x1a/0x20 > [<ffffffffa038e05f>] init_dummy+0x1f/0x30 [dummy_module] > [<ffffffff81002144>] do_one_initcall+0xd4/0x210 > [<ffffffff811b52c2>] ? __vunmap+0xc2/0x110 > [<ffffffff810f8889>] load_module+0x16a9/0x1b30 > [<ffffffff810f3d30>] ? store_uevent+0x70/0x70 > [<ffffffff810f49b9>] ? copy_module_from_fd.isra.44+0x129/0x180 > [<ffffffff810f8ec6>] SyS_finit_module+0xa6/0xd0 > [<ffffffff8166cf29>] system_call_fastpath+0x12/0x17 > > Successfully tested by me. > > Cc: Jonathan Corbet <corbet at lwn.net> > Cc: Andrew Morton <akpm at linux-foundation.org> > Cc: Rusty Russell <rusty at rustcorp.com.au> > Cc: "H. Peter Anvin" <hpa at zytor.com> > Cc: Andi Kleen <ak at linux.intel.com> > Cc: Masami Hiramatsu <masami.hiramatsu.pt at hitachi.com> > Cc: Fabian Frederick <fabf at skynet.be> > Cc: vgoyal at redhat.com > Cc: isimatu.yasuaki at jp.fujitsu.com > Cc: jbaron at akamai.com > Cc: linux-doc at vger.kernel.org > Cc: kexec at lists.infradead.org > Cc: linux-api at vger.kernel.org > Signed-off-by: Prarit Bhargava <prarit at redhat.com> > > [v2]: add /proc/sys/kernel/panic_on_warn, additional documentation, modify > !slowpath cases > [v3]: use proc_dointvec_minmax() in sysctl handler > [v4]: remove !slowpath cases, and add __read_mostly > [v5]: change to panic_on_warn, re-alphabetize Documentation/sysctl/kernel.txt > [v6]: disable on kdump kernel to avoid bogus panicks. > [v7]: swithch to core param, and remove change from v6 This looks good to me. Acked-by: WANG Chao <chaowang at redhat.com> > --- > Documentation/kdump/kdump.txt | 7 ++++++ > Documentation/kernel-parameters.txt | 3 +++ > Documentation/sysctl/kernel.txt | 40 +++++++++++++++++++++++------------ > include/linux/kernel.h | 1 + > include/uapi/linux/sysctl.h | 1 + > kernel/panic.c | 15 ++++++++++++- > kernel/sysctl.c | 9 ++++++++ > kernel/sysctl_binary.c | 1 + > 8 files changed, 62 insertions(+), 15 deletions(-) > > diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt > index 6c0b9f2..bc4bd5a 100644 > --- a/Documentation/kdump/kdump.txt > +++ b/Documentation/kdump/kdump.txt > @@ -471,6 +471,13 @@ format. Crash is available on Dave Anderson's site at the following URL: > > http://people.redhat.com/~anderson/ > > +Trigger Kdump on WARN() > +======================= > + > +The kernel parameter, panic_on_warn, calls panic() in all WARN() paths. This > +will cause a kdump to occur at the panic() call. In cases where a user wants > +to specify this during runtime, /proc/sys/kernel/panic_on_warn can be set to 1 > +to achieve the same behaviour. > > Contact > ======= > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index 4c81a86..ea5d57c 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2509,6 +2509,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > timeout < 0: reboot immediately > Format: <timeout> > > + panic_on_warn panic() instead of WARN(). Useful to cause kdump > + on a WARN(). > + > crash_kexec_post_notifiers > Run kdump after running panic-notifiers and dumping > kmsg. This only for the users who doubt kdump always > diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt > index 57baff5..b5d0c85 100644 > --- a/Documentation/sysctl/kernel.txt > +++ b/Documentation/sysctl/kernel.txt > @@ -54,8 +54,9 @@ show up in /proc/sys/kernel: > - overflowuid > - panic > - panic_on_oops > -- panic_on_unrecovered_nmi > - panic_on_stackoverflow > +- panic_on_unrecovered_nmi > +- panic_on_warn > - pid_max > - powersave-nap [ PPC only ] > - printk > @@ -527,19 +528,6 @@ the recommended setting is 60. > > ============================================================== > > -panic_on_unrecovered_nmi: > - > -The default Linux behaviour on an NMI of either memory or unknown is > -to continue operation. For many environments such as scientific > -computing it is preferable that the box is taken out and the error > -dealt with than an uncorrected parity/ECC error get propagated. > - > -A small number of systems do generate NMI's for bizarre random reasons > -such as power management so the default is off. That sysctl works like > -the existing panic controls already in that directory. > - > -============================================================== > - > panic_on_oops: > > Controls the kernel's behaviour when an oops or BUG is encountered. > @@ -563,6 +551,30 @@ This file shows up if CONFIG_DEBUG_STACKOVERFLOW is enabled. > > ============================================================== > > +panic_on_unrecovered_nmi: > + > +The default Linux behaviour on an NMI of either memory or unknown is > +to continue operation. For many environments such as scientific > +computing it is preferable that the box is taken out and the error > +dealt with than an uncorrected parity/ECC error get propagated. > + > +A small number of systems do generate NMI's for bizarre random reasons > +such as power management so the default is off. That sysctl works like > +the existing panic controls already in that directory. > + > +============================================================== > + > +panic_on_warn: > + > +Calls panic() in the WARN() path when set to 1. This is useful to avoid > +a kernel rebuild when attempting to kdump at the location of a WARN(). > + > +0: only WARN(), default behaviour. > + > +1: call panic() after printing out WARN() location. > + > +============================================================== > + > perf_cpu_time_max_percent: > > Hints to the kernel how much CPU time it should be allowed to > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index 3d770f55..d60d31d 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -422,6 +422,7 @@ extern int panic_timeout; > 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_stackoverflow; > /* > * Only to be used by arch init code. If the user over-wrote the default > diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h > index 43aaba1..0956373 100644 > --- a/include/uapi/linux/sysctl.h > +++ b/include/uapi/linux/sysctl.h > @@ -153,6 +153,7 @@ enum > KERN_MAX_LOCK_DEPTH=74, /* int: rtmutex's maximum lock depth */ > KERN_NMI_WATCHDOG=75, /* int: enable/disable nmi watchdog */ > KERN_PANIC_ON_NMI=76, /* int: whether we will panic on an unrecovered */ > + KERN_PANIC_ON_WARN=77, /* int: call panic() in WARN() functions */ > }; > > > diff --git a/kernel/panic.c b/kernel/panic.c > index d09dc5c..db37c35 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -23,6 +23,7 @@ > #include <linux/sysrq.h> > #include <linux/init.h> > #include <linux/nmi.h> > +#include <linux/crash_dump.h> > > #define PANIC_TIMER_STEP 100 > #define PANIC_BLINK_SPD 18 > @@ -33,6 +34,7 @@ static int pause_on_oops; > static int pause_on_oops_flag; > static DEFINE_SPINLOCK(pause_on_oops_lock); > static bool crash_kexec_post_notifiers; > +int panic_on_warn __read_mostly; > > int panic_timeout = CONFIG_PANIC_TIMEOUT; > EXPORT_SYMBOL_GPL(panic_timeout); > @@ -420,13 +422,23 @@ static void warn_slowpath_common(const char *file, int line, void *caller, > { > disable_trace_on_warning(); > > - pr_warn("------------[ cut here ]------------\n"); > + if (!panic_on_warn) > + pr_warn("------------[ cut here ]------------\n"); > pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n", > raw_smp_processor_id(), current->pid, file, line, caller); > > if (args) > vprintk(args->fmt, args->args); > > + if (panic_on_warn) { > + /* > + * A flood of WARN()s may occur. Prevent further WARN()s > + * from panicking the system. > + */ > + panic_on_warn = 0; > + panic("panic_on_warn set ...\n"); > + } > + > print_modules(); > dump_stack(); > print_oops_end_marker(); > @@ -484,6 +496,7 @@ EXPORT_SYMBOL(__stack_chk_fail); > > core_param(panic, panic_timeout, int, 0644); > core_param(pause_on_oops, pause_on_oops, int, 0644); > +core_param(panic_on_warn, panic_on_warn, int, 0644); > > static int __init setup_crash_kexec_post_notifiers(char *s) > { > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 15f2511..7c54ff7 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -1104,6 +1104,15 @@ static struct ctl_table kern_table[] = { > .proc_handler = proc_dointvec, > }, > #endif > + { > + .procname = "panic_on_warn", > + .data = &panic_on_warn, > + .maxlen = sizeof(int), > + .mode = 0644, > + .proc_handler = proc_dointvec_minmax, > + .extra1 = &zero, > + .extra2 = &one, > + }, > { } > }; > > diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c > index 9a4f750..7e7746a 100644 > --- a/kernel/sysctl_binary.c > +++ b/kernel/sysctl_binary.c > @@ -137,6 +137,7 @@ static const struct bin_table bin_kern_table[] = { > { CTL_INT, KERN_COMPAT_LOG, "compat-log" }, > { CTL_INT, KERN_MAX_LOCK_DEPTH, "max_lock_depth" }, > { CTL_INT, KERN_PANIC_ON_NMI, "panic_on_unrecovered_nmi" }, > + { CTL_INT, KERN_PANIC_ON_WARN, "panic_on_warn" }, > {} > }; > > -- > 1.7.9.3 > > > _______________________________________________ > kexec mailing list > kexec at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec
