Commit-ID: 707e59ba494372a90d245f18b0c78982caa88e48
Gitweb: http://git.kernel.org/tip/707e59ba494372a90d245f18b0c78982caa88e48
Author: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
AuthorDate: Fri, 22 Apr 2016 13:05:31 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sat, 23 Apr 2016 13:40:02 +0200
xen/qspinlock: Don't kick CPU if IRQ is not initialized
The following commit:
1fb3a8b2cfb2 ("xen/spinlock: Fix locking path engaging too soon under PVHVM.")
... moved the initalization of the kicker interrupt until after
native_cpu_up() is called.
However, when using qspinlocks, a CPU may try to kick another CPU that is
spinning (because it has not yet initialized its kicker interrupt), resulting
in the following crash during boot:
kernel BUG at /build/linux-Ay7j_C/linux-4.4.0/drivers/xen/events/events_base.c:1210!
invalid opcode: 0000 [#1] SMP
...
RIP: 0010:[<ffffffff814c97c9>] [<ffffffff814c97c9>] xen_send_IPI_one+0x59/0x60
...
Call Trace:
[<ffffffff8102be9e>] xen_qlock_kick+0xe/0x10
[<ffffffff810cabc2>] __pv_queued_spin_unlock+0xb2/0xf0
[<ffffffff810ca6d1>] ? __raw_callee_save___pv_queued_spin_unlock+0x11/0x20
[<ffffffff81052936>] ? check_tsc_warp+0x76/0x150
[<ffffffff81052aa6>] check_tsc_sync_source+0x96/0x160
[<ffffffff81051e28>] native_cpu_up+0x3d8/0x9f0
[<ffffffff8102b315>] xen_hvm_cpu_up+0x35/0x80
[<ffffffff8108198c>] _cpu_up+0x13c/0x180
[<ffffffff81081a4a>] cpu_up+0x7a/0xa0
[<ffffffff81f80dfc>] smp_init+0x7f/0x81
[<ffffffff81f5a121>] kernel_init_freeable+0xef/0x212
[<ffffffff81817f30>] ? rest_init+0x80/0x80
[<ffffffff81817f3e>] kernel_init+0xe/0xe0
[<ffffffff8182488f>] ret_from_fork+0x3f/0x70
[<ffffffff81817f30>] ? rest_init+0x80/0x80
To fix this, only send the kick if the target CPU's interrupt has been
initialized. This check isn't racy, because the target is waiting for
the spinlock, so it won't have initialized the interrupt in the
meantime.
Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/xen/spinlock.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 9e2ba5c..f42e78d 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -27,6 +27,12 @@ static bool xen_pvspin = true;
static void xen_qlock_kick(int cpu)
{
+ int irq = per_cpu(lock_kicker_irq, cpu);
+
+ /* Don't kick if the target's kicker interrupt is not initialized. */
+ if (irq == -1)
+ return;
+
xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
}
--
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