[PATCH] generic-pidhash-2.5.36-J2, BK-curr

This is the latest version of the generic pidhash patch.  The biggest
change is the removal of separately allocated pid structures: they are
now part of the task structure and the first task that uses a PID will
provide the pid structure.  Task refcounting is used to avoid the
freeing of the task structure before every member of a process group or
session has exited.

This approach has a number of advantages besides the performance gains.
Besides simplifying the whole hashing code significantly, attach_pid()
is now fundamentally atomic and can be called during create_process()
without worrying about task-list side-effects.  It does not have to
re-search the pidhash to find out about raced PID-adding either, and
attach_pid() cannot fail due to OOM.  detach_pid() can do a simple
put_task_struct() instead of the kmem_cache_free().

The only minimal downside is the potential pending task structures after
session leaders or group leaders have exited - but the number of orphan
sessions and process groups is usually very low - and even if it's
higher, this can be regarded as a slow execution of the final
deallocation of the session leader, not some additional burden.

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index ee937c477b83..2d5fae6293c5 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -8,7 +8,7 @@ export-objs = signal.o sys.o kmod.o context.o ksyms.o pm.o exec_domain.o \
 obj-y     = sched.o fork.o exec_domain.o panic.o printk.o \
 	    module.o exit.o itimer.o time.o softirq.o resource.o \
 	    sysctl.o capability.o ptrace.o timer.o user.o \
-	    signal.o sys.o kmod.o context.o futex.o platform.o
+	    signal.o sys.o kmod.o context.o futex.o platform.o pid.o
 
 obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
 obj-$(CONFIG_SMP) += cpu.o