From: Laurent Dufour <ldufour@linux.vnet.ibm.com>
To: paulmck@linux.vnet.ibm.com, peterz@infradead.org,
akpm@linux-foundation.org, kirill@shutemov.name,
ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net,
jack@suse.cz, Matthew Wilcox <willy@infradead.org>,
benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
hpa@zytor.com, Will Deacon <will.deacon@arm.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com,
npiggin@gmail.com, bsingharora@gmail.com,
Tim Chen <tim.c.chen@linux.intel.com>,
linuxppc-dev@lists.ozlabs.org, x86@kernel.org
Subject: [PATCH v5 17/22] mm: Try spin lock in speculative path
Date: Wed, 11 Oct 2017 15:52:41 +0200 [thread overview]
Message-ID: <1507729966-10660-18-git-send-email-ldufour@linux.vnet.ibm.com> (raw)
In-Reply-To: <1507729966-10660-1-git-send-email-ldufour@linux.vnet.ibm.com>
There is a deadlock when a CPU is doing a speculative page fault and
another one is calling do_unmap().
The deadlock occurred because the speculative path try to spinlock the
pte while the interrupt are disabled. When the other CPU in the
unmap's path has locked the pte then is waiting for all the CPU to
invalidate the TLB. As the CPU doing the speculative fault have the
interrupt disable it can't invalidate the TLB, and can't get the lock.
Since we are in a speculative path, we can race with other mm action.
So let assume that the lock may not get acquired and fail the
speculative page fault.
Here are the stacks captured during the deadlock:
CPU 0
native_flush_tlb_others+0x7c/0x260
flush_tlb_mm_range+0x6a/0x220
tlb_flush_mmu_tlbonly+0x63/0xc0
unmap_page_range+0x897/0x9d0
? unmap_single_vma+0x7d/0xe0
? release_pages+0x2b3/0x360
unmap_single_vma+0x7d/0xe0
unmap_vmas+0x51/0xa0
unmap_region+0xbd/0x130
do_munmap+0x279/0x460
SyS_munmap+0x53/0x70
CPU 1
do_raw_spin_lock+0x14e/0x160
_raw_spin_lock+0x5d/0x80
? pte_map_lock+0x169/0x1b0
pte_map_lock+0x169/0x1b0
handle_pte_fault+0xbf2/0xd80
? trace_hardirqs_on+0xd/0x10
handle_speculative_fault+0x272/0x280
handle_speculative_fault+0x5/0x280
__do_page_fault+0x187/0x580
trace_do_page_fault+0x52/0x260
do_async_page_fault+0x19/0x70
async_page_fault+0x28/0x30
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
---
mm/memory.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index eff40abfc1a6..d1278fc15a91 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2476,7 +2476,8 @@ static bool pte_spinlock(struct vm_fault *vmf)
goto out;
vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
- spin_lock(vmf->ptl);
+ if (unlikely(!spin_trylock(vmf->ptl)))
+ goto out;
if (vma_has_changed(vmf)) {
spin_unlock(vmf->ptl);
@@ -2521,8 +2522,20 @@ static bool pte_map_lock(struct vm_fault *vmf)
if (vma_has_changed(vmf))
goto out;
- pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd,
- vmf->address, &ptl);
+ /*
+ * Same as pte_offset_map_lock() except that we call
+ * spin_trylock() in place of spin_lock() to avoid race with
+ * unmap path which may have the lock and wait for this CPU
+ * to invalidate TLB but this CPU has irq disabled.
+ * Since we are in a speculative patch, accept it could fail
+ */
+ ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
+ pte = pte_offset_map(vmf->pmd, vmf->address);
+ if (unlikely(!spin_trylock(ptl))) {
+ pte_unmap(pte);
+ goto out;
+ }
+
if (vma_has_changed(vmf)) {
pte_unmap_unlock(pte, ptl);
goto out;
--
2.7.4
next prev parent reply other threads:[~2017-10-11 13:53 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-11 13:52 [PATCH v5 00/22] Speculative page faults Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 01/22] x86/mm: Define CONFIG_SPF Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 02/22] powerpc/mm: " Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 03/22] mm: Dont assume page-table invariance during faults Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 04/22] mm: Prepare for FAULT_FLAG_SPECULATIVE Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 05/22] mm: Introduce pte_spinlock " Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 06/22] mm: VMA sequence count Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 07/22] mm: Protect VMA modifications using " Laurent Dufour
2017-10-26 10:18 ` Andrea Arcangeli
2017-11-02 15:16 ` Laurent Dufour
2017-11-02 17:25 ` Laurent Dufour
2017-11-02 20:08 ` Andrea Arcangeli
2017-11-06 9:47 ` Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 08/22] mm: RCU free VMAs Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 09/22] mm: Cache some VMA fields in the vm_fault structure Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 10/22] mm: Protect SPF handler against anon_vma changes Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 11/22] mm/migrate: Pass vm_fault pointer to migrate_misplaced_page() Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 12/22] mm: Introduce __lru_cache_add_active_or_unevictable Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 13/22] mm: Introduce __maybe_mkwrite() Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 14/22] mm: Introduce __vm_normal_page() Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 15/22] mm: Introduce __page_add_new_anon_rmap() Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 16/22] mm: Provide speculative fault infrastructure Laurent Dufour
2017-10-11 13:52 ` Laurent Dufour [this message]
2017-10-11 13:52 ` [PATCH v5 18/22] mm: Adding speculative page fault failure trace events Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 19/22] perf: Add a speculative page fault sw event Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 20/22] perf tools: Add support for the SPF perf event Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 21/22] x86/mm: Add speculative pagefault handling Laurent Dufour
2017-10-11 13:52 ` [PATCH v5 22/22] powerpc/mm: Add speculative page fault Laurent Dufour
2017-10-26 8:14 ` [v5,22/22] " kemi
2017-11-02 14:11 ` Laurent Dufour
2017-11-06 10:27 ` Sergey Senozhatsky
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