Messages in this thread | | | Date | Thu, 19 Jun 2008 13:02:14 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] X86: reboot-notify additions |
| |
* Cliff Wickman <cpw@sgi.com> wrote:
> From: Cliff Wickman <cpw@sgi.com> > > X86 reboot-notify additions. > > This patch adds scans of the "reboot_notifier_list" callback chain in > a three other places where the kernel is being stopped and/or restarted. > > Adds calls to blocking_notifier_call_chain() in: > crash_kexec(), emergency_restart(), sys_kexec_load() > > In the crash_kexec() and emergency_restart() cases it is indicated to the > called-back function that the system is not in a sane state, so that > it can avoid taking a lock or some such potentially blocking action. > > These callbacks are important to a partition system. The stopped kernel needs > to inform other partitions of their need to disconnect (stop sharing memory). > > Diffed against 2.6.26-rc6 > > Signed-off-by: Cliff Wickman <cpw@sgi.com> > --- > include/linux/notifier.h | 4 ++++ > kernel/kexec.c | 5 +++++ > kernel/sys.c | 1 + > 3 files changed, 10 insertions(+) > > Index: linux/include/linux/notifier.h > =================================================================== > --- linux.orig/include/linux/notifier.h > +++ linux/include/linux/notifier.h > @@ -202,6 +202,10 @@ static inline int notifier_to_errno(int > #define SYS_RESTART SYS_DOWN > #define SYS_HALT 0x0002 /* Notify of system halt */ > #define SYS_POWER_OFF 0x0003 /* Notify of system power off */ > +#define SYS_INSANE 0x0004 /* Notify of system error/panic/oops */ > +/* For the SYS_INSANE case, no locks should be taken by the called-back > + * function. The kernel is ready for an immediate reboot. > + */ > > #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ > > Index: linux/kernel/kexec.c > =================================================================== > --- linux.orig/kernel/kexec.c > +++ linux/kernel/kexec.c > @@ -1001,6 +1001,9 @@ asmlinkage long sys_kexec_load(unsigned > if (result) > goto out; > } > + > + blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL); > + > /* Install the new kernel, and Uninstall the old */ > image = xchg(dest_image, image); > > @@ -1068,6 +1071,8 @@ void crash_kexec(struct pt_regs *regs) > if (!locked) { > if (kexec_crash_image) { > struct pt_regs fixed_regs; > + blocking_notifier_call_chain(&reboot_notifier_list, > + SYS_INSANE, NULL); > crash_setup_regs(&fixed_regs, regs); > crash_save_vmcoreinfo(); > machine_crash_shutdown(&fixed_regs); > Index: linux/kernel/sys.c > =================================================================== > --- linux.orig/kernel/sys.c > +++ linux/kernel/sys.c > @@ -270,6 +270,7 @@ out_unlock: > */ > void emergency_restart(void) > { > + blocking_notifier_call_chain(&reboot_notifier_list, SYS_INSANE, NULL); > machine_emergency_restart(); > } > EXPORT_SYMBOL_GPL(emergency_restart);
i dont think this is a good idea. reboot_notifier_list is a blocking notifier, i.e. it comes with a notifier->rwsem read-write mutex that is taken when blocking_notifier_call_chain() is executed.
i.e. this patch puts a sleeping mutex operation (a down_read()) into a highly critical code path of the kernel. This will decrease the reliability of the kernel.
what exactly are you trying to achieve?
Ingo
| |