A cpu in the mm_cpumask could go offline before we send the invalidate
IPI causing us to wait forever. Avoid this by only waiting for online
cpus.
We are seeing a softlockup reporting during shutdown. The stack
trace shows us that we are inside default_send_IPI_mask_logical:
BUG: soft lockup - CPU#0 stuck for 11s! [lmt-udev:23605]
Pid: 23605, comm: lmt-udev Tainted: G WC 3.2.7 #1
EIP: 0060:[<8101eec6>] EFLAGS: 00000202 CPU: 0
EIP is at flush_tlb_others_ipi+0x8a/0xba
Call Trace:
[<8101f0bb>] flush_tlb_mm+0x5e/0x62
[<8101e36c>] pud_populate+0x2c/0x31
[<8101e409>] pgd_alloc+0x98/0xc7
[<8102c881>] mm_init.isra.38+0xcc/0xf3
[<8102cbc2>] dup_mm+0x68/0x34e
[<8139bbae>] ? _cond_resched+0xd/0x21
[<810a5b7c>] ? kmem_cache_alloc+0x26/0xe2
[<8102d421>] ? copy_process+0x556/0xda6
[<8102d641>] copy_process+0x776/0xda6
[<8102dd5e>] do_fork+0xcb/0x1d4
[<810a8c96>] ? do_sync_write+0xd3/0xd3
[<810a94ab>] ? vfs_read+0x95/0xa2
[<81008850>] sys_clone+0x20/0x25
[<8139d8c5>] ptregs_clone+0x15/0x30
[<8139d7f7>] ? sysenter_do_call+0x12/0x26
Before the softlock, we see the following kernel warning:
WARNING: at ../../arch/x86/kernel/apic/ipi.c:113 default_send_IPI_mask_logical+0x58/0x73()
Pid: 23605, comm: lmt-udev Tainted: G C 3.2.7 #1
Call Trace:
[<8102e666>] warn_slowpath_common+0x68/0x7d
[<81016c36>] ? default_send_IPI_mask_logical+0x58/0x73
[<8102e68f>] warn_slowpath_null+0x14/0x18
[<81016c36>] default_send_IPI_mask_logical+0x58/0x73
[<8101eec2>] flush_tlb_others_ipi+0x86/0xba
[<8101f0bb>] flush_tlb_mm+0x5e/0x62
[<8101e36c>] pud_populate+0x2c/0x31
[<8101e409>] pgd_alloc+0x98/0xc7
[<8102c881>] mm_init.isra.38+0xcc/0xf3
[<8102cbc2>] dup_mm+0x68/0x34e
[<8139bbae>] ? _cond_resched+0xd/0x21
[<810a5b7c>] ? kmem_cache_alloc+0x26/0xe2
[<8102d421>] ? copy_process+0x556/0xda6
[<8102d641>] copy_process+0x776/0xda6
[<8102dd5e>] do_fork+0xcb/0x1d4
[<810a8c96>] ? do_sync_write+0xd3/0xd3
[<810a94ab>] ? vfs_read+0x95/0xa2
[<81008850>] sys_clone+0x20/0x25
[<8139d8c5>] ptregs_clone+0x15/0x30
[<8139d7f7>] ? sysenter_do_call+0x12/0x26
So we are sending an IPI to a cpu which is now offline. Once a cpu is offline,
it will no longer respond to IPIs. This explains the softlockup.
Addresses http://crosbug.com/31737
Changes in V2:
* bitmap_and is not atomic so use a temporary bitmask
Signed-off-by: Mandeep Singh Baines <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: Tejun Heo <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Olof Johansson <[email protected]>
---
arch/x86/mm/tlb.c | 9 ++++++++-
1 files changed, 8 insertions(+), 1 deletions(-)
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index d6c0418..231a0b9 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -185,6 +185,8 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
f->flush_mm = mm;
f->flush_va = va;
if (cpumask_andnot(to_cpumask(f->flush_cpumask), cpumask, cpumask_of(smp_processor_id()))) {
+ DECLARE_BITMAP(tmp_cpumask, NR_CPUS);
+
/*
* We have to send the IPI only to
* CPUs affected.
@@ -192,8 +194,13 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
apic->send_IPI_mask(to_cpumask(f->flush_cpumask),
INVALIDATE_TLB_VECTOR_START + sender);
- while (!cpumask_empty(to_cpumask(f->flush_cpumask)))
+ /* Only wait for online cpus */
+ do {
+ cpumask_and(to_cpumask(tmp_cpumask),
+ to_cpumask(f->flush_cpumask),
+ cpu_online_mask);
cpu_relax();
+ } while (!cpumask_empty(to_cpumask(tmp_cpumask)));
}
f->flush_mm = NULL;
--
1.7.7.3