During those "cannot-do-anything" times, I even got kernel messages. One example:

[998882.032583] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[998882.032589] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[998882.032594] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[998882.032602]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[998882.032614]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[998882.032628]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[998882.032637] Call Trace:
[998882.032650]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[998882.032654]  [<c05a47c5>] mutex_lock+0x25/0x40
[998882.032660]  [<c020e1fe>] real_lookup+0x2e/0x110
[998882.032664]  [<c020fc05>] do_lookup+0x95/0xc0
[998882.032669]  [<c021043d>] __link_path_walk+0x54d/0xb60
[998882.032673]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[998882.032677]  [<c0210bf6>] path_walk+0x46/0xa0
[998882.032681]  [<c0210d59>] do_path_lookup+0x59/0x90
[998882.032685]  [<c02118a1>] user_path_at+0x41/0x80
[998882.032691]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[998882.032696]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[998882.032702]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[998882.032706]  [<c0209a60>] vfs_lstat+0x20/0x30
[998882.032710]  [<c0209a89>] sys_lstat64+0x19/0x30
[998882.032715]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[998882.032721]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[998882.032727]  [<c010344c>] syscall_call+0x7/0xb
[999002.032195] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[999002.032202] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[999002.032208] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[999002.032218]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[999002.032232]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[999002.032245]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[999002.032258] Call Trace:
[999002.032274]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[999002.032283]  [<c05a47c5>] mutex_lock+0x25/0x40
[999002.032291]  [<c020e1fe>] real_lookup+0x2e/0x110
[999002.032298]  [<c020fc05>] do_lookup+0x95/0xc0
[999002.032304]  [<c021043d>] __link_path_walk+0x54d/0xb60
[999002.032312]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[999002.032318]  [<c0210bf6>] path_walk+0x46/0xa0
[999002.032324]  [<c0210d59>] do_path_lookup+0x59/0x90
[999002.032331]  [<c02118a1>] user_path_at+0x41/0x80
[999002.032338]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[999002.032348]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[999002.032354]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[999002.032358]  [<c0209a60>] vfs_lstat+0x20/0x30
[999002.032362]  [<c0209a89>] sys_lstat64+0x19/0x30
[999002.032367]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[999002.032374]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[999002.032379]  [<c010344c>] syscall_call+0x7/0xb
[999122.032597] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[999122.032603] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[999122.032608] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[999122.032616]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[999122.032632]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[999122.032640]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[999122.032649] Call Trace:
[999122.032662]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[999122.032667]  [<c05a47c5>] mutex_lock+0x25/0x40
[999122.032673]  [<c020e1fe>] real_lookup+0x2e/0x110
[999122.032677]  [<c020fc05>] do_lookup+0x95/0xc0
[999122.032681]  [<c021043d>] __link_path_walk+0x54d/0xb60
[999122.032686]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[999122.032691]  [<c0210bf6>] path_walk+0x46/0xa0
[999122.032695]  [<c0210d59>] do_path_lookup+0x59/0x90
[999122.032699]  [<c02118a1>] user_path_at+0x41/0x80
[999122.032705]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[999122.032710]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[999122.032716]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[999122.032721]  [<c0209a60>] vfs_lstat+0x20/0x30
[999122.032725]  [<c0209a89>] sys_lstat64+0x19/0x30
[999122.032730]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[999122.032736]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[999122.032742]  [<c010344c>] syscall_call+0x7/0xb
[999242.032601] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[999242.032609] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[999242.032614] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[999242.032622]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[999242.032635]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[999242.032645]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[999242.032654] Call Trace:
[999242.032667]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[999242.032672]  [<c05a47c5>] mutex_lock+0x25/0x40
[999242.032678]  [<c020e1fe>] real_lookup+0x2e/0x110
[999242.032682]  [<c020fc05>] do_lookup+0x95/0xc0
[999242.032686]  [<c021043d>] __link_path_walk+0x54d/0xb60
[999242.032691]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[999242.032695]  [<c0210bf6>] path_walk+0x46/0xa0
[999242.032699]  [<c0210d59>] do_path_lookup+0x59/0x90
[999242.032704]  [<c02118a1>] user_path_at+0x41/0x80
[999242.032709]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[999242.032715]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[999242.032720]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[999242.032725]  [<c0209a60>] vfs_lstat+0x20/0x30
[999242.032729]  [<c0209a89>] sys_lstat64+0x19/0x30
[999242.032734]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[999242.032741]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[999242.032746]  [<c010344c>] syscall_call+0x7/0xb
[999362.032591] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[999362.032597] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[999362.032601] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[999362.032609]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[999362.032621]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[999362.032635]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[999362.032645] Call Trace:
[999362.032658]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[999362.032663]  [<c05a47c5>] mutex_lock+0x25/0x40
[999362.032668]  [<c020e1fe>] real_lookup+0x2e/0x110
[999362.032673]  [<c020fc05>] do_lookup+0x95/0xc0
[999362.032678]  [<c021043d>] __link_path_walk+0x54d/0xb60
[999362.032683]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[999362.032687]  [<c0210bf6>] path_walk+0x46/0xa0
[999362.032691]  [<c0210d59>] do_path_lookup+0x59/0x90
[999362.032696]  [<c02118a1>] user_path_at+0x41/0x80
[999362.032702]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[999362.032708]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[999362.032714]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[999362.032718]  [<c0209a60>] vfs_lstat+0x20/0x30
[999362.032722]  [<c0209a89>] sys_lstat64+0x19/0x30
[999362.032728]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[999362.032735]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[999362.032740]  [<c010344c>] syscall_call+0x7/0xb
[999482.032233] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[999482.032240] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[999482.032246] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[999482.032255]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[999482.032269]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[999482.032282]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[999482.032294] Call Trace:
[999482.032311]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[999482.032317]  [<c05a47c5>] mutex_lock+0x25/0x40
[999482.032325]  [<c020e1fe>] real_lookup+0x2e/0x110
[999482.032332]  [<c020fc05>] do_lookup+0x95/0xc0
[999482.032338]  [<c021043d>] __link_path_walk+0x54d/0xb60
[999482.032345]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[999482.032351]  [<c0210bf6>] path_walk+0x46/0xa0
[999482.032357]  [<c0210d59>] do_path_lookup+0x59/0x90
[999482.032364]  [<c02118a1>] user_path_at+0x41/0x80
[999482.032373]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[999482.032383]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[999482.032391]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[999482.032397]  [<c0209a60>] vfs_lstat+0x20/0x30
[999482.032402]  [<c0209a89>] sys_lstat64+0x19/0x30
[999482.032410]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[999482.032418]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[999482.032426]  [<c010344c>] syscall_call+0x7/0xb
[999602.032611] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[999602.032619] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[999602.032624] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[999602.032633]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[999602.032648]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[999602.032659]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[999602.032672] Call Trace:
[999602.032686]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[999602.032691]  [<c05a47c5>] mutex_lock+0x25/0x40
[999602.032697]  [<c020e1fe>] real_lookup+0x2e/0x110
[999602.032701]  [<c020fc05>] do_lookup+0x95/0xc0
[999602.032705]  [<c021043d>] __link_path_walk+0x54d/0xb60
[999602.032710]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[999602.032714]  [<c0210bf6>] path_walk+0x46/0xa0
[999602.032718]  [<c0210d59>] do_path_lookup+0x59/0x90
[999602.032722]  [<c02118a1>] user_path_at+0x41/0x80
[999602.032728]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[999602.032736]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[999602.032744]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[999602.032752]  [<c0209a60>] vfs_lstat+0x20/0x30
[999602.032756]  [<c0209a89>] sys_lstat64+0x19/0x30
[999602.032762]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[999602.032768]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[999602.032774]  [<c010344c>] syscall_call+0x7/0xb
[999722.032579] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[999722.032585] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[999722.032589] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[999722.032598]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[999722.032610]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[999722.032624]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[999722.032633] Call Trace:
[999722.032646]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[999722.032652]  [<c05a47c5>] mutex_lock+0x25/0x40
[999722.032658]  [<c020e1fe>] real_lookup+0x2e/0x110
[999722.032662]  [<c020fc05>] do_lookup+0x95/0xc0
[999722.032666]  [<c021043d>] __link_path_walk+0x54d/0xb60
[999722.032672]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[999722.032679]  [<c0210bf6>] path_walk+0x46/0xa0
[999722.032686]  [<c0210d59>] do_path_lookup+0x59/0x90
[999722.032694]  [<c02118a1>] user_path_at+0x41/0x80
[999722.032701]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[999722.032710]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[999722.032717]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[999722.032723]  [<c0209a60>] vfs_lstat+0x20/0x30
[999722.032728]  [<c0209a89>] sys_lstat64+0x19/0x30
[999722.032734]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[999722.032742]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[999722.032754]  [<c010344c>] syscall_call+0x7/0xb
[999842.032611] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[999842.032624] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[999842.032629] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[999842.032638]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[999842.032651]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[999842.032667]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[999842.032678] Call Trace:
[999842.032693]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[999842.032700]  [<c05a47c5>] mutex_lock+0x25/0x40
[999842.032706]  [<c020e1fe>] real_lookup+0x2e/0x110
[999842.032712]  [<c020fc05>] do_lookup+0x95/0xc0
[999842.032718]  [<c021043d>] __link_path_walk+0x54d/0xb60
[999842.032725]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[999842.032729]  [<c0210bf6>] path_walk+0x46/0xa0
[999842.032733]  [<c0210d59>] do_path_lookup+0x59/0x90
[999842.032737]  [<c02118a1>] user_path_at+0x41/0x80
[999842.032743]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[999842.032749]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[999842.032754]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[999842.032758]  [<c0209a60>] vfs_lstat+0x20/0x30
[999842.032762]  [<c0209a89>] sys_lstat64+0x19/0x30
[999842.032768]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[999842.032774]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[999842.032779]  [<c010344c>] syscall_call+0x7/0xb
[999962.032595] INFO: task gvfsd-trash:2063 blocked for more than 120 seconds.
[999962.032601] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[999962.032606] gvfsd-trash   D 0001ae75     0  2063      1 0x00000000
[999962.032614]  d59f7da0 00000086 00000000 0001ae75 00000000 c087c6c0 d5825c5c c087c6c0
[999962.032630]  7a06b2df 00038c42 c087c6c0 c087c6c0 d5825c5c c087c6c0 c087c6c0 dd11a200
[999962.032639]  7a04da23 00038c42 d58259b0 cb0f4078 cb0f407c ffffffff d59f7dcc c05a48a6
[999962.032648] Call Trace:
[999962.032661]  [<c05a48a6>] __mutex_lock_slowpath+0xc6/0x130
[999962.032665]  [<c05a47c5>] mutex_lock+0x25/0x40
[999962.032671]  [<c020e1fe>] real_lookup+0x2e/0x110
[999962.032676]  [<c020fc05>] do_lookup+0x95/0xc0
[999962.032680]  [<c021043d>] __link_path_walk+0x54d/0xb60
[999962.032684]  [<c020f246>] ? path_to_nameidata+0x36/0x50
[999962.032689]  [<c0210bf6>] path_walk+0x46/0xa0
[999962.032693]  [<c0210d59>] do_path_lookup+0x59/0x90
[999962.032697]  [<c02118a1>] user_path_at+0x41/0x80
[999962.032702]  [<c01304cc>] ? kmap_atomic_prot+0x4c/0xf0
[999962.032708]  [<c01e2f60>] ? __do_fault+0x3a0/0x4b0
[999962.032713]  [<c02099ca>] vfs_fstatat+0x3a/0x70
[999962.032718]  [<c0209a60>] vfs_lstat+0x20/0x30
[999962.032722]  [<c0209a89>] sys_lstat64+0x19/0x30
[999962.032727]  [<c05a7f2b>] ? do_page_fault+0x19b/0x380
[999962.032733]  [<c0237492>] ? sys_inotify_add_watch+0xc2/0x100
[999962.032739]  [<c010344c>] syscall_call+0x7/0xb