randconfig testing found a bootup lockup in drivers/char/esp.c - find the fix below. Not sure why it became more prominent in 2.6.25-rc4, the bug seems rather old and i've been doing allyesconfig bootups for ages with CONFIG_ESP enabled.
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Subject: drivers/char/esp.c: fix bootup lockup
From: Ingo Molnar <mingo@xxxxxxx>
Date: Fri Mar 07 10:47:43 CET 2008
fix this bootup lockup:
PM: Adding info for No Bus:ttyP63
ttyP32 at 0x0240 (irq = 0) is an ESP primary port
BUG: spinlock lockup on CPU#0, swapper/1, f56dd004
Pid: 1, comm: swapper Not tainted 2.6.25-rc4-sched-devel.git-x86-latest.git #402 [<c03ac6f4>] _raw_spin_lock+0x134/0x140
[<c08649be>] _spin_lock_irqsave+0x5e/0x80
[<c0b9fbfe>] ? espserial_init+0x2be/0x6e0
[<c0b9fbfe>] espserial_init+0x2be/0x6e0
[<c0b877a3>] kernel_init+0x83/0x260
[<c0b9f940>] ? espserial_init+0x0/0x6e0
[<c010416a>] ? restore_nocheck_notrace+0x0/0xe
[<c0b87720>] ? kernel_init+0x0/0x260
[<c0b87720>] ? kernel_init+0x0/0x260
[<c0104507>] kernel_thread_helper+0x7/0x10
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kzalloc() is not the way to initialize spinlocks anymore.