Hi all,

I'm currently investigating a regression that has showed up with my last
git pull yesterday. Bisecting the commits showed bf726e "semaphore: fix"
to be the culprit, reverting it fixed the issue.

Symptoms: During heavy filesystem usage (e.g. a kernel compile) I get
several compiler processes in uninterruptible sleep, blocking all i/o on
the filesystem. System is an Intel Core 2 Quad running a 64bit kernel and
userspace. Filesystem is xfs on top of lvm. See below for the output of
sysrq-w.

Sven



task PC stack pid father
gcc D ffff81000105c100 0 13923 13913
ffff8101ed51be18 0000000000000082 ffff8101ed51beb0 00000010802bf7b8
ffffffff807d7100 ffffffff807d7100 ffffffff807d7100 ffffffff807d7100
ffffffff807d7100 ffffffff807d7100 ffffffff807d3ca0 ffffffff807d7100
Call Trace:
[] __mutex_lock_slowpath+0xd8/0x270
[] ? do_path_lookup+0x91/0x220
[] ? strncpy_from_user+0x3a/0x50
[] mutex_lock+0x9/0x10
[] do_unlinkat+0xaa/0x1d0
[] ? up_read+0x9/0x10
[] ? do_page_fault+0x3ec/0x850
[] sys_unlink+0x11/0x20
[] system_call_after_swapgs+0x7b/0x80

gcc D ffff810001070100 0 13924 13920
ffff8101f6971e18 0000000000000082 ffff8101f6971eb0 00000010802bf7b8
ffffffff807d7100 ffffffff807d7100 ffffffff807d7100 ffffffff807d7100
ffffffff807d7100 ffffffff807d7100 ffffffff807d3ca0 ffffffff807d7100
Call Trace:
[] __mutex_lock_slowpath+0xd8/0x270
[] ? do_path_lookup+0x91/0x220
[] ? strncpy_from_user+0x3a/0x50
[] mutex_lock+0x9/0x10
[] do_unlinkat+0xaa/0x1d0
[] ? up_read+0x9/0x10
[] ? do_page_fault+0x3ec/0x850
[] sys_unlink+0x11/0x20
[] system_call_after_swapgs+0x7b/0x80

gcc D ffff81000107a100 0 13932 13931
ffff8101ed447e18 0000000000000086 ffff8101ed447eb0 00000010802bf7b8
ffffffff807d7100 ffffffff807d7100 ffffffff807d7100 ffffffff807d7100
ffffffff807d7100 ffffffff807d7100 ffffffff807d3ca0 ffffffff807d7100
Call Trace:
[] __mutex_lock_slowpath+0xd8/0x270
[] ? do_path_lookup+0x91/0x220
[] ? strncpy_from_user+0x3a/0x50
[] mutex_lock+0x9/0x10
[] do_unlinkat+0xaa/0x1d0
[] ? up_read+0x9/0x10
[] ? do_page_fault+0x3ec/0x850
[] sys_unlink+0x11/0x20
[] system_call_after_swapgs+0x7b/0x80

sync D ffff81000105c100 0 13996 9142
ffff8101ed481d48 0000000000000086 0000000000000000 ffffffff807d7100
ffffffff807d7100 ffffffff807d7100 ffffffff807d7100 ffffffff807d7100
ffffffff807d7100 ffffffff807d7100 ffffffff807d3ca0 ffffffff807d7100
Call Trace:
[] __down_read+0x79/0xb7
[] down_read+0x9/0x10
[] xfs_ilock+0x44/0x80
[] xfs_sync_inodes+0x3e8/0x6b0
[] xfs_syncsub+0x15e/0x2d0
[] ? _spin_unlock+0x9/0x40
[] xfs_sync+0x44/0x60
[] xfs_fs_sync_super+0x37/0x100
[] ? _spin_unlock_irq+0x9/0x40
[] ? __down_read+0xa5/0xb7
[] ? __up_read+0x46/0xb0
[] sync_filesystems+0xdf/0x130
[] do_sync+0x39/0x80
[] sys_sync+0xe/0x20
[] system_call_after_swapgs+0x7b/0x80

gcc D ffff810001066100 0 14008 14007
ffff8101f69b5898 0000000000000086 ffff8101fb9e4de0 0000000100000000
ffffffff807d7100 ffffffff807d7100 ffffffff807d7100 ffffffff807d7100
ffffffff807d7100 ffffffff807d7100 ffffffff807d3ca0 ffffffff807d7100
Call Trace:
[] ? down_trylock+0x36/0x50
[] schedule_timeout+0x95/0xd0
[] ? xfs_buf_get_flags+0xa8/0x170
[] __down+0x5a/0x90
[] down+0x45/0x50
[] xlog_state_get_iclog_space+0xa2/0x200
[] xlog_write+0x11c/0x530
[] xfs_log_write+0x40/0x70
[] _xfs_trans_commit+0x2e8/0x3d0
[] ? igrab+0x2f/0x50
[] xfs_create+0x426/0x480
[] xfs_vn_mknod+0x15b/0x2a0
[] xfs_vn_create+0xb/0x10
[] vfs_create+0xe8/0x180
[] do_filp_open+0x69f/0x9c0
[] ? _spin_unlock+0x9/0x40
[] ? get_unused_fd_flags+0x105/0x130
[] do_sys_open+0x5c/0xf0
[] sys_open+0x1b/0x20
[] system_call_after_swapgs+0x7b/0x80

gcc D ffff81000105c100 0 14011 14010
ffff8101ed51fe18 0000000000000082 0000000000000000 00000010802b1704
ffffffff807d7100 ffffffff807d7100 ffffffff807d7100 ffffffff807d7100
ffffffff807d7100 ffffffff807d7100 ffffffff807d3ca0 ffffffff807d7100
Call Trace:
[] __mutex_lock_slowpath+0xd8/0x270
[] ? do_path_lookup+0x91/0x220
[] ? strncpy_from_user+0x3a/0x50
[] mutex_lock+0x9/0x10
[] do_unlinkat+0xaa/0x1d0
[] ? up_read+0x9/0x10
[] ? do_page_fault+0x3ec/0x850
[] sys_unlink+0x11/0x20
[] system_call_after_swapgs+0x7b/0x80

gcc D ffff81000107a100 0 14012 13987
ffff8101ed409e18 0000000000000082 0000000000000000 00000010802b1704
ffffffff807d7100 ffffffff807d7100 ffffffff807d7100 ffffffff807d7100
ffffffff807d7100 ffffffff807d7100 ffffffff807d3ca0 ffffffff807d7100
Call Trace:
[] __mutex_lock_slowpath+0xd8/0x270
[] ? do_path_lookup+0x91/0x220
[] ? strncpy_from_user+0x3a/0x50
[] mutex_lock+0x9/0x10
[] do_unlinkat+0xaa/0x1d0
[] ? up_read+0x9/0x10
[] ? do_page_fault+0x3ec/0x850
[] sys_unlink+0x11/0x20
[] system_call_after_swapgs+0x7b/0x80
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