fs/pstore: provide panic data even in suspend
Subsystems (2)
PATCH v4 1/1 fs/pstore: provide panic data even in suspend
From: Dongdong Yang <[email protected]>
If system restart after panic, this patch also enables panic and oops messages which in suspend context to be logged into ramoops console buffer where it can be read back at some later point.
--- fs/pstore/ram.c | 16 ++++++++++++++++ include/linux/printk.h | 6 ++++++ kernel/printk/printk.c | 6 ++++++ 3 files changed, 28 insertions(+)
fs/pstore/ram.c +16 -0
@@ -642,8 +642,23 @@ static void ramoops_register_dummy(void) } } +static int ramoops_console_notify (struct notifier_block *this, +unsigned long event,void *ptr) +{ +pr_emerg ("ramoops unlock console ...\n" ); +emergency_unlock_console (); + +return 0 ; +} + +static struct notifier_block ramoop_nb = { + .notifier_call = ramoops_console_notify, + .priority =INT_MAX , +}; +static int __init ramoops_init (void ) { +atomic_notifier_chain_register (&panic_notifier_list, &ramoop_nb);ramoops_register_dummy ();return platform_driver_register (&ramoops_driver); }
@@ -654,6 +669,7 @@ static void __exit ramoops_exit(void)platform_driver_unregister (&ramoops_driver);platform_device_unregister (dummy);kfree (dummy_data); +atomic_notifier_chain_unregister (&panic_notifier_list, &ramoop_nb); }module_exit (ramoops_exit);
include/linux/printk.h +6 -0
@@ -230,6 +230,12 @@ static inline void show_regs_print_info(const char *log_lvl) }#endif +/* +* Enables printk() before emergency_restart +* if we go into suspend states and run into oops. +*/ +void emergency_unlock_console (void ); + extern asmlinkage void dump_stack(void) __cold;#ifndef pr_fmt
kernel/printk/printk.c +6 -0
@@ -2107,6 +2107,12 @@ void resume_console(void)console_unlock (); } +void emergency_unlock_console (void ) +{ +if (oops_in_progress && panic_timeout !=0 && console_suspended) +resume_console (); +} +/** * console_cpu_notify - print deferred console messages after CPU hotplug * @self: notifier struct
Signature · 9 lines
2.5.0 v4: - Move declaration emergency_unlock_console to printk.h from pstore_ram.h - Update sign-off information. Thanks, Dongdong Yang
Petr Mladek
maintainerQuoted 74 lines · On Mon 2015-08-17 16:51:39, [email protected] wrote:
From: Dongdong Yang <[email protected]>
If system restart after panic, this patch also enables panic and oops messages which in suspend context to be logged into ramoops console buffer where it can be read back at some later point.
Signed-off-by Dongdong Yang <[email protected]>Signed-off-by Linghua Gu <[email protected]>Signed-off-by Hui Du <[email protected]>--- fs/pstore/ram.c | 16 ++++++++++++++++ include/linux/printk.h | 6 ++++++ kernel/printk/printk.c | 6 ++++++ 3 files changed, 28 insertions(+)fs/pstore/ram.c +16
-0@@ -642,8 +642,23 @@ static void ramoops_register_dummy(void) } } +static int ramoops_console_notify (struct notifier_block *this, +unsigned long event,void *ptr) +{ +pr_emerg ("ramoops unlock console ...\n" ); +emergency_unlock_console (); + +return 0 ; +} + +static struct notifier_block ramoop_nb = { + .notifier_call = ramoops_console_notify, + .priority =INT_MAX , +}; +static int __init ramoops_init (void ) { +atomic_notifier_chain_register (&panic_notifier_list, &ramoop_nb);ramoops_register_dummy ();return platform_driver_register (&ramoops_driver); }@@ -654,6 +669,7 @@ static void __exit ramoops_exit(void)platform_driver_unregister (&ramoops_driver);platform_device_unregister (dummy);kfree (dummy_data); +atomic_notifier_chain_unregister (&panic_notifier_list, &ramoop_nb); }module_exit (ramoops_exit);include/linux/printk.h +6
-0@@ -230,6 +230,12 @@ static inline void show_regs_print_info(const char *log_lvl) }#endif +/* +* Enables printk() before emergency_restart +* if we go into suspend states and run into oops. +*/ +void emergency_unlock_console (void ); + extern asmlinkage void dump_stack(void) __cold;#ifndef pr_fmtkernel/printk/printk.c +0
-0
kernel/printk/printk.c void resume_console(void) · line 2113
Quoted 7 lines
kernel/printk/printk.c +4
-0@@ -2107,6 +2107,12 @@ void resume_console(void)console_unlock (); } +void emergency_unlock_console (void ) +{ +if (oops_in_progress && panic_timeout !=0 && console_suspended) +resume_console ();
IMHO, you need to put "console_sem" down if you want to test "console_suspended". And you must keep it down until you resume the console to avoid a race => we could not call resume_console() in the current form.
Also I am a bit nervous that this operation is not symmetric and the console will stay resumed. Please look at bust_spinlocks(), how this function is used in panic(), and see how the "oops_in_progress" is handled.
To be honest, I do not understand this code in details enough and I do not have time to investigate it at the moment. I just use a common sense to produce this feedback. Others might give you a better feedback. It is possible that this should get handled a more generic way and not by a ramoops specific handler.
BTW: Have you tested this with more consoles attached? I wonder if other consoles are still usable in this situation and if they will not block the output to ramoops.
Best Regards,
Petr
Quoted 15 lines
kernel/printk/printk.c +2
-0+} +/** * console_cpu_notify - print deferred console messages after CPU hotplug * @self: notifier struct Signature · 9 lines
2.5.0 v4: - Move declaration emergency_unlock_console to printk.h from pstore_ram.h - Update sign-off information. Thanks, Dongdong Yang