Commit 74614de1 authored by Tony Luck's avatar Tony Luck Committed by Linus Torvalds
Browse files

mm/memory-failure.c: don't let collect_procs() skip over processes for MF_ACTION_REQUIRED 



When Linux sees an "action optional" machine check (where h/w has reported
an error that is not in the current execution path) we generally do not
want to signal a process, since most processes do not have a SIGBUS
handler - we'd just prematurely terminate the process for a problem that
they might never actually see.

task_early_kill() decides whether to consider a process - and it checks
whether this specific process has been marked for early signals with
"prctl", or if the system administrator has requested early signals for
all processes using /proc/sys/vm/memory_failure_early_kill.

But for MF_ACTION_REQUIRED case we must not defer.  The error is in the
execution path of the current thread so we must send the SIGBUS
immediatley.

Fix by passing a flag argument through collect_procs*() to
task_early_kill() so it knows whether we can defer or must take action.

Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Chen Gong <gong.chen@linux.jf.intel.com>
Cc: <stable@vger.kernel.org>	[3.2+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a70ffcac

mm/memory-failure.c

+12 −9
Original line number Diff line number Diff line
@@ -380,10 +380,12 @@ static void kill_procs(struct list_head *to_kill, int forcekill, int trapno, 
	}

}



static int task_early_kill(struct task_struct *tsk)

static int task_early_kill(struct task_struct *tsk, int force_early)

{

	if (!tsk->mm)

		return 0;

	if (force_early)

		return 1;

	if (tsk->flags & PF_MCE_PROCESS)

		return !!(tsk->flags & PF_MCE_EARLY);

	return sysctl_memory_failure_early_kill;
@@ -393,7 +395,7 @@ static int task_early_kill(struct task_struct *tsk) 
 * Collect processes when the error hit an anonymous page.

 */

static void collect_procs_anon(struct page *page, struct list_head *to_kill,

			      struct to_kill **tkc)

			      struct to_kill **tkc, int force_early)

{

	struct vm_area_struct *vma;

	struct task_struct *tsk;
@@ -409,7 +411,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill, 
	for_each_process (tsk) {

		struct anon_vma_chain *vmac;



		if (!task_early_kill(tsk))

		if (!task_early_kill(tsk, force_early))

			continue;

		anon_vma_interval_tree_foreach(vmac, &av->rb_root,

					       pgoff, pgoff) {
@@ -428,7 +430,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill, 
 * Collect processes when the error hit a file mapped page.

 */

static void collect_procs_file(struct page *page, struct list_head *to_kill,

			      struct to_kill **tkc)

			      struct to_kill **tkc, int force_early)

{

	struct vm_area_struct *vma;

	struct task_struct *tsk;
@@ -439,7 +441,7 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill, 
	for_each_process(tsk) {

		pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);



		if (!task_early_kill(tsk))

		if (!task_early_kill(tsk, force_early))

			continue;



		vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
@@ -465,7 +467,8 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill, 
 * First preallocate one tokill structure outside the spin locks,

 * so that we can kill at least one process reasonably reliable.

 */

static void collect_procs(struct page *page, struct list_head *tokill)

static void collect_procs(struct page *page, struct list_head *tokill,

				int force_early)

{

	struct to_kill *tk;
@@ -476,9 +479,9 @@ static void collect_procs(struct page *page, struct list_head *tokill) 
	if (!tk)

		return;

	if (PageAnon(page))

		collect_procs_anon(page, tokill, &tk);

		collect_procs_anon(page, tokill, &tk, force_early);

	else

		collect_procs_file(page, tokill, &tk);

		collect_procs_file(page, tokill, &tk, force_early);

	kfree(tk);

}
@@ -963,7 +966,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn, 
	 * there's nothing that can be done.

	 */

	if (kill)

		collect_procs(ppage, &tokill);

		collect_procs(ppage, &tokill, flags & MF_ACTION_REQUIRED);



	ret = try_to_unmap(ppage, ttu);

	if (ret != SWAP_SUCCESS)

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