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  1. 23 May, 2008 4 commits
    • Christian Borntraeger's avatar
      stop_machine: make stop_machine_run more virtualization friendly · 3401a61e
      Christian Borntraeger authored 
      On kvm I have seen some rare hangs in stop_machine when I used more guest
cpus than hosts cpus. e.g. 32 guest cpus on 1 host cpu triggered the
hang quite often. I could also reproduce the problem on a 4 way z/VM host with
a 64 way guest.

It turned out that the guest was consuming all available cpus mostly for
spinning on scheduler locks like rq->lock. This is expected as the threads are
calling yield all the time.
The problem is now, that the host scheduling decisings together with the guest
scheduling decisions and spinlocks not being fair managed to create an
interesting scenario similar to a live lock. (Sometimes the hang resolved
itself after some minutes)

Changing stop_machine to yield the cpu to the hypervisor when yielding inside
the guest fixed the problem for me. While I am not completely happy with this
patch, I think it causes no harm and it really improves the situation for me.

I used cpu_relax for yielding to the hypervisor, does that work on all
architectures?

p.s.: If you want to reproduce the problem, cpu hotplug and kprobes use
stop_machine_run and both triggered the problem after some retries.
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      3401a61e
    • Matti Linnanvuori's avatar
      doc: add a chapter about trylock functions [Bug 9011] · 4d2e7d0d
      Matti Linnanvuori authored 
      Add a chapter about trylock functions.
http://bugzilla.kernel.org/show_bug.cgi?id=9011Signed-off-by: default avatarMatti Linnanvuori <mattilinnanvuori@yahoo.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (removed down_trylock)
      4d2e7d0d
    • Denis V. Lunev's avatar
      modules: proper cleanup of kobject without CONFIG_SYSFS · 34e4e2fe
      Denis V. Lunev authored 
      kobject: '<NULL>' (ffffffffa0104050): is not initialized, yet kobject_put() is being called.
------------[ cut here ]------------
WARNING: at /home/den/src/linux-netns26/lib/kobject.c:583 kobject_put+0x53/0x55()
Modules linked in: ipv6 nfsd lockd nfs_acl auth_rpcgss sunrpc exportfs ide_cd_mod cdrom button [last unloaded: pktgen]
comm: rmmod Tainted: G        W 2.6.26-rc3 #585
Call Trace:
  [<ffffffff802359ab>] warn_on_slowpath+0x58/0x7a
  [<ffffffff80236aca>] ? printk+0x67/0x69
  [<ffffffff80236aca>] ? printk+0x67/0x69
  [<ffffffff80324289>] kobject_put+0x53/0x55
  [<ffffffff8025e2ee>] free_module+0x87/0xfa
  [<ffffffff8025fee5>] sys_delete_module+0x178/0x1e1
  [<ffffffff804b1e70>] ? lockdep_sys_exit_thunk+0x35/0x67
  [<ffffffff804b1dff>] ? trace_hardirqs_on_thunk+0x35/0x3a
  [<ffffffff8020c0bb>] system_call_after_swapgs+0x7b/0x80
---[ end trace 8f5aafa7f6406cf8 ]---

mod->mkobj.kobj is not initialized without CONFIG_SYSFS. Do not call
kobject_put in this case.
Signed-off-by: default avatarDenis V. Lunev <den@openvz.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      34e4e2fe
    • Cyrill Gorcunov's avatar
      module loading ELF handling: use SELFMAG instead of numeric constant · c4ea6fcf
      Cyrill Gorcunov authored 
      Signed-off-by: default avatarCyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      c4ea6fcf
  3. 21 May, 2008 25 commits
  5. 20 May, 2008 11 commits
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