With Rawhide kernel-PAE, I'm seeing what I can best describe as "semi-lockups" on my system.  The X server keeps responding, and I can for example launch thunderbird and read email, but filesystem operations block and attempts to open new terminal windows or to ssh in from a remote host hang.  The existing terminal windows even stop responding to keystrokes, although like I said, some other X applications continue to work.

When this happens, I see messages like this in dmesg:

Jul 19 13:28:52 jik2 kernel: INFO: task events/0:9 blocked for more than 120 seconds.
Jul 19 13:28:52 jik2 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jul 19 13:28:52 jik2 kernel: events/0      D 00000002  6000     9      2 0x00000000
Jul 19 13:28:52 jik2 kernel: f70d5cec 00000092 f405cf60 00000002 f70c599c c0afc3b8 c0c40fc0 f70c599c
Jul 19 13:28:52 jik2 kernel: f70d5cdc c0c40fc0 c0c40fc0 00000002 00000000 00000000 00000000 4870c435
Jul 19 13:28:52 jik2 kernel: 0000006e c3151fc0 f70c5700 503ca15f f70d5ce0 c0476746 503ca15f 503ca15f
Jul 19 13:28:52 jik2 kernel: Call Trace:
Jul 19 13:28:52 jik2 kernel: [<c0476746>] ? trace_hardirqs_on_caller+0x26/0x155
Jul 19 13:28:52 jik2 kernel: [<c047688e>] ? trace_hardirqs_on+0x19/0x2c
Jul 19 13:28:52 jik2 kernel: [<c0828ef1>] __mutex_lock_common+0x1cd/0x32b
Jul 19 13:28:52 jik2 kernel: [<c068986b>] ? process_echoes+0x3b/0x26b
Jul 19 13:28:52 jik2 kernel: [<c0829142>] mutex_lock_nested+0x41/0x5a
Jul 19 13:28:52 jik2 kernel: [<c068986b>] ? process_echoes+0x3b/0x26b
Jul 19 13:28:52 jik2 kernel: [<c068986b>] process_echoes+0x3b/0x26b
Jul 19 13:28:52 jik2 kernel: [<c0689abb>] n_tty_write_wakeup+0x20/0x62
Jul 19 13:28:52 jik2 kernel: [<c0688115>] tty_wakeup+0x3d/0x74
Jul 19 13:28:52 jik2 kernel: [<c068f2cf>] pty_write+0x5b/0x74
Jul 19 13:28:52 jik2 kernel: [<c068625b>] tty_put_char+0x38/0x4e
Jul 19 13:28:52 jik2 kernel: [<c06896f6>] do_output_char+0x97/0x1d1
Jul 19 13:28:52 jik2 kernel: [<c06899fb>] process_echoes+0x1cb/0x26b
Jul 19 13:28:52 jik2 kernel: [<c068b8da>] n_tty_receive_buf+0x98a/0xe14
Jul 19 13:28:52 jik2 kernel: [<c068e0fc>] ? flush_to_ldisc+0x47/0x17f
Jul 19 13:28:52 jik2 kernel: [<c068e0fc>] ? flush_to_ldisc+0x47/0x17f
Jul 19 13:28:52 jik2 kernel: [<c068e0fc>] ? flush_to_ldisc+0x47/0x17f
Jul 19 13:28:52 jik2 kernel: [<c0476746>] ? trace_hardirqs_on_caller+0x26/0x155
Jul 19 13:28:52 jik2 kernel: [<c047688e>] ? trace_hardirqs_on+0x19/0x2c
Jul 19 13:28:52 jik2 kernel: [<c068e19b>] flush_to_ldisc+0xe6/0x17f
Jul 19 13:28:52 jik2 kernel: [<c045f285>] worker_thread+0x194/0x275
Jul 19 13:28:52 jik2 kernel: [<c045f243>] ? worker_thread+0x152/0x275
Jul 19 13:28:52 jik2 kernel: [<c068e0b5>] ? flush_to_ldisc+0x0/0x17f
Jul 19 13:28:52 jik2 kernel: [<c0464166>] ? autoremove_wake_function+0x0/0x55
Jul 19 13:28:52 jik2 kernel: [<c045f0f1>] ? worker_thread+0x0/0x275
Jul 19 13:28:52 jik2 kernel: [<c0463e10>] kthread+0x76/0x7b
Jul 19 13:28:52 jik2 kernel: [<c0463d9a>] ? kthread+0x0/0x7b
Jul 19 13:28:52 jik2 kernel: [<c040b5df>] kernel_thread_helper+0x7/0x10
Jul 19 13:28:52 jik2 kernel: INFO: lockdep is turned off.

I usually have to reset my system to get it back into a usable state.