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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2011-09-30 11:57:58 +0200
committerClark Williams <williams@redhat.com>2012-03-01 09:28:53 -0600
commit25ee004d77b1366b03ef54576bde10a2f883d1ac (patch)
tree57be7f50705174a3898a40e2d3a088b58b843be9 /include
parentbec8cc0486d35315f9bb26b39175178e45595d4f (diff)
workqueue: Fix cpuhotplug trainwreck
The current workqueue code does crazy stuff on cpu unplug, it relies on forced affine breakage, thereby violating per-cpu expectations. Worse, it tries to re-attach to a cpu if the thing comes up again before all previously queued works are finished. This breaks (admittedly bonkers) cpu-hotplug use that relies on a down-up cycle to push all usage away. Introduce a new WQ_NON_AFFINE flag that indicates a per-cpu workqueue will not respect cpu affinity and use this to migrate all its pending works to whatever cpu is doing cpu-down. This also adds a warning for queue_on_cpu() users which warns when its used on WQ_NON_AFFINE workqueues for the API implies you care about what cpu things are ran on when such workqueues cannot guarantee this. For the rest, simply flush all per-cpu works and don't mess about. This also means that currently all workqueues that are manually flushing things on cpu-down in order to provide the per-cpu guarantee no longer need to do so. In short, we tell the WQ what we want it to do, provide validation for this and loose ~250 lines of code. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include')
-rw-r--r--include/linux/cpu.h6
-rw-r--r--include/linux/workqueue.h5
2 files changed, 7 insertions, 4 deletions
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index c46ec3ecd661..72e90bbf625a 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -66,8 +66,10 @@ enum {
/* migration should happen before other stuff but after perf */
CPU_PRI_PERF = 20,
CPU_PRI_MIGRATION = 10,
- /* prepare workqueues for other notifiers */
- CPU_PRI_WORKQUEUE = 5,
+
+ CPU_PRI_WORKQUEUE_ACTIVE = 5, /* prepare workqueues for others */
+ CPU_PRI_NORMAL = 0,
+ CPU_PRI_WORKQUEUE_INACTIVE = -5, /* flush workqueues after others */
};
#define CPU_ONLINE 0x0002 /* CPU (unsigned)v is up */
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 0d556deb497b..d68ead81b52b 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -254,9 +254,10 @@ enum {
WQ_MEM_RECLAIM = 1 << 3, /* may be used for memory reclaim */
WQ_HIGHPRI = 1 << 4, /* high priority */
WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */
+ WQ_NON_AFFINE = 1 << 6, /* free to move works around cpus */
- WQ_DRAINING = 1 << 6, /* internal: workqueue is draining */
- WQ_RESCUER = 1 << 7, /* internal: workqueue has rescuer */
+ WQ_DRAINING = 1 << 7, /* internal: workqueue is draining */
+ WQ_RESCUER = 1 << 8, /* internal: workqueue has rescuer */
WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */