Here is one more backtrace of the same crash.
[ 9199.462928] Call Trace:
[ 9199.462928] <IRQ> [<ffffffff80435886>] ? _spin_lock+0x3a/0x42
[ 9199.462928] [<ffffffffa00964f4>] ? :sata_sil:sil_interrupt+0x2b/0x275
[ 9199.462928] [<ffffffff8025f0e6>] ? handle_IRQ_event+0x47/0x8e
[ 9199.462928] [<ffffffff802605a2>] ? handle_level_irq+0xae/0x116
[ 9199.462928] [<ffffffff8020e13e>] ? do_IRQ+0x4e/0x9a
[ 9199.462928] [<ffffffff8037d4cc>] ? evtchn_do_upcall+0x13c/0x1fc
[ 9199.462928] [<ffffffff8020bbde>] ? do_hypervisor_callback+0x1e/0x30
[ 9199.462928] <EOI> [<ffffffff802e48d1>] ? dummy_inode_permission+0x0/0x3
[ 9199.462928] [<ffffffff8037cbf9>] ? xen_poll_irq+0x67/0x74
[ 9199.462928] [<ffffffff8037fb06>] ? xen_spin_wait+0xfa/0x139
[ 9199.462928] [<ffffffff80435cfd>] ? lock_kernel+0x4f/0x63
[ 9199.462928] [<ffffffffa04327b4>] ? :nfs:nfs_permission+0xb0/0x15f
[ 9199.462928] [<ffffffff80291e65>] ? permission+0xb5/0x118
[ 9199.462928] [<ffffffff80293469>] ? __link_path_walk+0x145/0xdfa
[ 9199.462928] [<ffffffffa044020a>] ? :nfs:nfs_sync_mapping_wait+0x151/0x33f
[ 9199.462928] [<ffffffff80294164>] ? path_walk+0x46/0x8b
[ 9199.462928] [<ffffffff80294490>] ? do_path_lookup+0x158/0x1ce
[ 9199.462928] [<ffffffff80294fd3>] ? __path_lookup_intent_open+0x56/0x97
[ 9199.462928] [<ffffffff80295109>] ? do_filp_open+0x9c/0x7c4
[ 9199.462928] [<ffffffff802888ff>] ? get_unused_fd_flags+0x74/0x13f
[ 9199.462928] [<ffffffff80288a10>] ? do_sys_open+0x46/0xc3
[ 9199.462928] [<ffffffff8020b528>] ? system_call+0x68/0x6d
[ 9199.462928] [<ffffffff8020b4c0>] ? system_call+0x0/0x6d
What is similar in all instances - it enters
... -> lock_kernel() -> xen_spin_wait() -> xen_poll_irq(),
then gets an interrupt, then enters
... -> :sata_sil:sil_interrupt() -> _spin_lock()
and gets kernel BUG at drivers/xen/core/spinlock.c:74
which is xen_spin_wait():
...
66 /* announce we're spinning */
67 spinning = &__get_cpu_var(spinning);
68 if (spinning->lock) {
69 BUG_ON(spinning->lock == lock);
70 if(raw_irqs_disabled()) {
71 BUG_ON(__get_cpu_var(spinning_bh).lock == lock);
72 spinning = &__get_cpu_var(spinning_irq);
73 } else {
74 BUG_ON(!in_softirq());
75 spinning = &__get_cpu_var(spinning_bh);
76 }
77 BUG_ON(spinning->lock);
78 }
...
So code thies to take BKL and spins there.
While spinning, interrupt arrives.
Interrupt handler tries to take another lock.
But xen_spin_wait() is not expecting attempt to take another lock when
not raw_irqs_disabled() and not in_softirq().
Here we are in interrupt handler, bit hard irq are not disabled.
Looks like check in line 70 is wrong.
Nikita
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