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| author |   Gautham R Shenoy <ego@in.ibm.com> | 2007-05-09 02:34:03 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-09 12:30:51 -0700 |
| commit | baaca49f415b25fdbe2a8f3c22b39929e450fbfd (patch) | |
| tree | b152b4235fc07fe56619bd3a2e975e5ca90b8c5b /include/linux/notifier.h | |
| parent | Extend notifier_call_chain to count nr_calls made (diff) | |
| download | linux-dev-baaca49f415b25fdbe2a8f3c22b39929e450fbfd.tar.xz linux-dev-baaca49f415b25fdbe2a8f3c22b39929e450fbfd.zip | |
Define and use new events,CPU_LOCK_ACQUIRE and CPU_LOCK_RELEASE
This is an attempt to provide an alternate mechanism for postponing
a hotplug event instead of using a global mechanism like lock_cpu_hotplug.
The proposal is to add two new events namely CPU_LOCK_ACQUIRE and
CPU_LOCK_RELEASE. The notification for these two events would be sent
out before and after a cpu_hotplug event respectively.
During the CPU_LOCK_ACQUIRE event, a cpu-hotplug-aware subsystem is
supposed to acquire any per-subsystem hotcpu mutex ( Eg. workqueue_mutex
in kernel/workqueue.c ).
During the CPU_LOCK_RELEASE release event the cpu-hotplug-aware subsystem
is supposed to release the per-subsystem hotcpu mutex.
The reasons for defining new events as opposed to reusing the existing events
like CPU_UP_PREPARE/CPU_UP_FAILED/CPU_ONLINE for locking/unlocking of
per-subsystem hotcpu mutexes are as follow:
- CPU_LOCK_ACQUIRE: All hotcpu mutexes are taken before subsystems
start handling pre-hotplug events like CPU_UP_PREPARE/CPU_DOWN_PREPARE
etc, thus ensuring a clean handling of these events.
- CPU_LOCK_RELEASE: The hotcpu mutexes will be released only after
all subsystems have handled post-hotplug events like CPU_DOWN_FAILED,
CPU_DEAD,CPU_ONLINE etc thereby ensuring that there are no subsequent
clashes amongst the interdependent subsystems after a cpu hotplugs.
This patch also uses __raw_notifier_call chain in _cpu_up to take care
of the dependency between the two consequetive calls to
raw_notifier_call_chain.
[akpm@linux-foundation.org: fix a bug]
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/notifier.h')
| -rw-r--r-- | include/linux/notifier.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/notifier.h b/include/linux/notifier.h index e34221bf8946..1903e5490c04 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -194,6 +194,8 @@ extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, #define CPU_DOWN_PREPARE 0x0005 /* CPU (unsigned)v going down */ #define CPU_DOWN_FAILED 0x0006 /* CPU (unsigned)v NOT going down */ #define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */ +#define CPU_LOCK_ACQUIRE 0x0008 /* Acquire all hotcpu locks */ +#define CPU_LOCK_RELEASE 0x0009 /* Release all hotcpu locks */ #endif /* __KERNEL__ */ #endif /* _LINUX_NOTIFIER_H */ |