Processes spinning forever, apparently in lock_timer_base()?

[Chuck Ebbert]

Looks like the same problem with spinlock unfairness we've seen
elsewhere: it seems to be looping here? Or is everyone stuck
just waiting for writeout?

lock_timer_base():
        for (;;) {
                tvec_base_t *prelock_base = timer->base;
                base = tbase_get_base(prelock_base);
                if (likely(base != NULL)) {
                        spin_lock_irqsave(&base->lock, *flags);
                        if (likely(prelock_base == timer->base))
                                return base;
                        /* The timer has migrated to another CPU */
                        spin_unlock_irqrestore(&base->lock, *flags);
                }
                cpu_relax();
        }

The problem goes away completely if filesystem are mounted
*without* noatime. Has happened in 2.6.20 through 2.6.22...

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=249563

Part of sysrq-t listing:

mysqld        D 000017c0  2196 23162   1562
       e383fcb8 00000082 61650954 000017c0 e383fc9c 00000000 c0407208 e383f000 
       a12b0434 00004d1d c6ed2c00 c6ed2d9c c200fa80 00000000 c0724640 f6c60540 
       c4ff3c70 00000508 00000286 c042ffcb e383fcc8 00014926 00000000 00000286 
Call Trace:
 [<c0407208>] do_IRQ+0xbd/0xd1
 [<c042ffcb>] lock_timer_base+0x19/0x35
 [<c04300df>] __mod_timer+0x9a/0xa4
 [<c060bb55>] schedule_timeout+0x70/0x8f
 [<c042fd37>] process_timeout+0x0/0x5
 [<c060bb50>] schedule_timeout+0x6b/0x8f
 [<c060b67c>] io_schedule_timeout+0x39/0x5d
 [<c0465eea>] congestion_wait+0x50/0x64
 [<c0438539>] autoremove_wake_function+0x0/0x35
 [<c04620e2>] balance_dirty_pages_ratelimited_nr+0x148/0x193
 [<c045e7fd>] generic_file_buffered_write+0x4c7/0x5d3


named         D 000017c0  2024  1454      1
       f722acb0 00000082 6165ed96 000017c0 c1523e80 c16f0c00 c16f20e0 f722a000 
       a12be87d 00004d1d f768ac00 f768ad9c c200fa80 00000000 00000000 f75bda80 
       c0407208 00000508 00000286 c042ffcb f722acc0 00020207 00000000 00000286 
Call Trace:
 [<c0407208>] do_IRQ+0xbd/0xd1
 [<c042ffcb>] lock_timer_base+0x19/0x35
 [<c04300df>] __mod_timer+0x9a/0xa4
 [<c060bb55>] schedule_timeout+0x70/0x8f
 [<c042fd37>] process_timeout+0x0/0x5
 [<c060bb50>] schedule_timeout+0x6b/0x8f
 [<c060b67c>] io_schedule_timeout+0x39/0x5d
 [<c0465eea>] congestion_wait+0x50/0x64
 [<c0438539>] autoremove_wake_function+0x0/0x35
 [<c04620e2>] balance_dirty_pages_ratelimited_nr+0x148/0x193
 [<c045e7fd>] generic_file_buffered_write+0x4c7/0x5d3


mysqld        D 000017c0  2196 23456   1562
       e9293cb8 00000082 616692ed 000017c0 e9293c9c 00000000 e9293cc8 e9293000 
       a12c8dd0 00004d1d c3d5ac00 c3d5ad9c c200fa80 00000000 c0724640 f6c60540 
       e9293d10 c07e1f00 00000286 c042ffcb e9293cc8 0002b57f 00000000 00000286 
Call Trace:
 [<c042ffcb>] lock_timer_base+0x19/0x35
 [<c04300df>] __mod_timer+0x9a/0xa4
 [<c060bb55>] schedule_timeout+0x70/0x8f
 [<c042fd37>] process_timeout+0x0/0x5
 [<c060bb50>] schedule_timeout+0x6b/0x8f
 [<c060b67c>] io_schedule_timeout+0x39/0x5d
 [<c0465eea>] congestion_wait+0x50/0x64
 [<c0438539>] autoremove_wake_function+0x0/0x35
 [<c04620e2>] balance_dirty_pages_ratelimited_nr+0x148/0x193
 [<c045e7fd>] generic_file_buffered_write+0x4c7/0x5d3
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