[3.13.y.z extended stable] Patch "mm/memory-failure.c: support use of a dedicated thread to handle SIGBUS(BUS_MCEERR_AO)" has been added to staging queue
Kamal Mostafa
kamal at canonical.com
Tue Jul 15 21:29:32 UTC 2014
This is a note to let you know that I have just added a patch titled
mm/memory-failure.c: support use of a dedicated thread to handle SIGBUS(BUS_MCEERR_AO)
to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue
This patch is scheduled to be released in version 3.13.11.5.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
------
>From 93d4ac3d8092ec38faa24154b1a3e388796a8da7 Mon Sep 17 00:00:00 2001
From: Naoya Horiguchi <n-horiguchi at ah.jp.nec.com>
Date: Wed, 4 Jun 2014 16:11:02 -0700
Subject: mm/memory-failure.c: support use of a dedicated thread to handle
SIGBUS(BUS_MCEERR_AO)
commit 3ba08129e38437561df44c36b7ea9081185d5333 upstream.
Currently memory error handler handles action optional errors in the
deferred manner by default. And if a recovery aware application wants
to handle it immediately, it can do it by setting PF_MCE_EARLY flag.
However, such signal can be sent only to the main thread, so it's
problematic if the application wants to have a dedicated thread to
handler such signals.
So this patch adds dedicated thread support to memory error handler. We
have PF_MCE_EARLY flags for each thread separately, so with this patch
AO signal is sent to the thread with PF_MCE_EARLY flag set, not the main
thread. If you want to implement a dedicated thread, you call prctl()
to set PF_MCE_EARLY on the thread.
Memory error handler collects processes to be killed, so this patch lets
it check PF_MCE_EARLY flag on each thread in the collecting routines.
No behavioral change for all non-early kill cases.
Tony said:
: The old behavior was crazy - someone with a multithreaded process might
: well expect that if they call prctl(PF_MCE_EARLY) in just one thread, then
: that thread would see the SIGBUS with si_code = BUS_MCEERR_A0 - even if
: that thread wasn't the main thread for the process.
[akpm at linux-foundation.org: coding-style fixes]
Signed-off-by: Naoya Horiguchi <n-horiguchi at ah.jp.nec.com>
Reviewed-by: Tony Luck <tony.luck at intel.com>
Cc: Kamil Iskra <iskra at mcs.anl.gov>
Cc: Andi Kleen <andi at firstfloor.org>
Cc: Borislav Petkov <bp at suse.de>
Cc: Chen Gong <gong.chen at linux.jf.intel.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
Documentation/vm/hwpoison.txt | 5 ++++
mm/memory-failure.c | 56 +++++++++++++++++++++++++++++++++----------
2 files changed, 48 insertions(+), 13 deletions(-)
diff --git a/Documentation/vm/hwpoison.txt b/Documentation/vm/hwpoison.txt
index 5500684..6ae89a9 100644
--- a/Documentation/vm/hwpoison.txt
+++ b/Documentation/vm/hwpoison.txt
@@ -84,6 +84,11 @@ PR_MCE_KILL
PR_MCE_KILL_EARLY: Early kill
PR_MCE_KILL_LATE: Late kill
PR_MCE_KILL_DEFAULT: Use system global default
+ Note that if you want to have a dedicated thread which handles
+ the SIGBUS(BUS_MCEERR_AO) on behalf of the process, you should
+ call prctl(PR_MCE_KILL_EARLY) on the designated thread. Otherwise,
+ the SIGBUS is sent to the main thread.
+
PR_MCE_KILL_GET
return current mode
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index e5f7031..ba1ab14 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -384,15 +384,44 @@ static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
}
}
-static int task_early_kill(struct task_struct *tsk, int force_early)
+/*
+ * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO)
+ * on behalf of the thread group. Return task_struct of the (first found)
+ * dedicated thread if found, and return NULL otherwise.
+ *
+ * We already hold read_lock(&tasklist_lock) in the caller, so we don't
+ * have to call rcu_read_lock/unlock() in this function.
+ */
+static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
+{
+ struct task_struct *t;
+
+ for_each_thread(tsk, t)
+ if ((t->flags & PF_MCE_PROCESS) && (t->flags & PF_MCE_EARLY))
+ return t;
+ return NULL;
+}
+
+/*
+ * Determine whether a given process is "early kill" process which expects
+ * to be signaled when some page under the process is hwpoisoned.
+ * Return task_struct of the dedicated thread (main thread unless explicitly
+ * specified) if the process is "early kill," and otherwise returns NULL.
+ */
+static struct task_struct *task_early_kill(struct task_struct *tsk,
+ int force_early)
{
+ struct task_struct *t;
if (!tsk->mm)
- return 0;
+ return NULL;
if (force_early)
- return 1;
- if (tsk->flags & PF_MCE_PROCESS)
- return !!(tsk->flags & PF_MCE_EARLY);
- return sysctl_memory_failure_early_kill;
+ return tsk;
+ t = find_early_kill_thread(tsk);
+ if (t)
+ return t;
+ if (sysctl_memory_failure_early_kill)
+ return tsk;
+ return NULL;
}
/*
@@ -414,16 +443,17 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
read_lock(&tasklist_lock);
for_each_process (tsk) {
struct anon_vma_chain *vmac;
+ struct task_struct *t = task_early_kill(tsk, force_early);
- if (!task_early_kill(tsk, force_early))
+ if (!t)
continue;
anon_vma_interval_tree_foreach(vmac, &av->rb_root,
pgoff, pgoff) {
vma = vmac->vma;
if (!page_mapped_in_vma(page, vma))
continue;
- if (vma->vm_mm == tsk->mm)
- add_to_kill(tsk, page, vma, to_kill, tkc);
+ if (vma->vm_mm == t->mm)
+ add_to_kill(t, page, vma, to_kill, tkc);
}
}
read_unlock(&tasklist_lock);
@@ -444,10 +474,10 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
read_lock(&tasklist_lock);
for_each_process(tsk) {
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+ struct task_struct *t = task_early_kill(tsk, force_early);
- if (!task_early_kill(tsk, force_early))
+ if (!t)
continue;
-
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
pgoff) {
/*
@@ -457,8 +487,8 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
* Assume applications who requested early kill want
* to be informed of all such data corruptions.
*/
- if (vma->vm_mm == tsk->mm)
- add_to_kill(tsk, page, vma, to_kill, tkc);
+ if (vma->vm_mm == t->mm)
+ add_to_kill(t, page, vma, to_kill, tkc);
}
}
read_unlock(&tasklist_lock);
--
1.9.1
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