[PATCH] checkpoint: conditionally schedule; check for fatal signals

[PATCH] checkpoint: conditionally schedule; check for fatal signals

[Nathan Lynch]

Long-running operations in the kernel should:

o  not monopolize the CPU
o  abort when asked

Put voluntary preemption points in ckpt_kread, ckpt_kwrite, and the
VMA-walking checkpoint code.  At the same points, return an error if a
fatal signal is pending; callers of these functions are supposed to be
checking return values.

Signed-off-by: Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
---
 kernel/checkpoint/sys.c |   10 ++++++++++
 mm/checkpoint.c         |    7 +++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/kernel/checkpoint/sys.c b/kernel/checkpoint/sys.c
index b761ec0..04e6277 100644
--- a/kernel/checkpoint/sys.c
+++ b/kernel/checkpoint/sys.c
@@ -72,6 +72,11 @@ int ckpt_kwrite(struct ckpt_ctx *ctx, void *addr, size_t count)
 	if (ckpt_test_error(ctx))
 		return ckpt_get_error(ctx);
 
+	if (fatal_signal_pending(current))
+		return -EINTR;
+
+	cond_resched();
+
 	ret = _ckpt_kwrite(ctx->file, addr, count);
 	if (ret < 0)
 		return ret;
@@ -103,6 +108,11 @@ int ckpt_kread(struct ckpt_ctx *ctx, void *addr, size_t count)
 	if (ckpt_test_error(ctx))
 		return ckpt_get_error(ctx);
 
+	if (fatal_signal_pending(current))
+		return -EINTR;
+
+	cond_resched();
+
 	ret = _ckpt_kread(ctx->file, addr, count);
 	if (ret < 0)
 		return ret;
diff --git a/mm/checkpoint.c b/mm/checkpoint.c
index 70300e8..6732a2e 100644
--- a/mm/checkpoint.c
+++ b/mm/checkpoint.c
@@ -310,6 +310,13 @@ static int vma_fill_pgarr(struct ckpt_ctx *ctx,
 		while (addr < end) {
 			struct page *page;
 
+			if (fatal_signal_pending(current)) {
+				cnt = -EINTR;
+				goto out;
+			}
+
+			cond_resched();
+
 			if (vma)
 				page = consider_private_page(vma, addr);
 			else
-- 
1.7.3.2

Re: [PATCH] checkpoint: conditionally schedule; check for fatal signals

[Matt Helsley]

On Thu, Nov 18, 2010 at 03:21:05PM -0600, Nathan Lynch wrote:
> Long-running operations in the kernel should:
> 
> o  not monopolize the CPU
> o  abort when asked
> 
> Put voluntary preemption points in ckpt_kread, ckpt_kwrite, and the
> VMA-walking checkpoint code.  At the same points, return an error if a
> fatal signal is pending; callers of these functions are supposed to be
> checking return values.

We do alot more than read/write the image -- e.g. collecting references at
the beginning prior to checkpoint. Perhaps should add some to the objhash
code too.

Cheers,
	-Matt Helsley

> 
> Signed-off-by: Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
> ---
>  kernel/checkpoint/sys.c |   10 ++++++++++
>  mm/checkpoint.c         |    7 +++++++
>  2 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/checkpoint/sys.c b/kernel/checkpoint/sys.c
> index b761ec0..04e6277 100644
> --- a/kernel/checkpoint/sys.c
> +++ b/kernel/checkpoint/sys.c
> @@ -72,6 +72,11 @@ int ckpt_kwrite(struct ckpt_ctx *ctx, void *addr, size_t count)
>  	if (ckpt_test_error(ctx))
>  		return ckpt_get_error(ctx);
> 
> +	if (fatal_signal_pending(current))
> +		return -EINTR;
> +
> +	cond_resched();
> +
>  	ret = _ckpt_kwrite(ctx->file, addr, count);
>  	if (ret < 0)
>  		return ret;
> @@ -103,6 +108,11 @@ int ckpt_kread(struct ckpt_ctx *ctx, void *addr, size_t count)
>  	if (ckpt_test_error(ctx))
>  		return ckpt_get_error(ctx);
> 
> +	if (fatal_signal_pending(current))
> +		return -EINTR;
> +
> +	cond_resched();
> +
>  	ret = _ckpt_kread(ctx->file, addr, count);
>  	if (ret < 0)
>  		return ret;
> diff --git a/mm/checkpoint.c b/mm/checkpoint.c
> index 70300e8..6732a2e 100644
> --- a/mm/checkpoint.c
> +++ b/mm/checkpoint.c
> @@ -310,6 +310,13 @@ static int vma_fill_pgarr(struct ckpt_ctx *ctx,
>  		while (addr < end) {
>  			struct page *page;
> 
> +			if (fatal_signal_pending(current)) {
> +				cnt = -EINTR;
> +				goto out;
> +			}
> +
> +			cond_resched();
> +
>  			if (vma)
>  				page = consider_private_page(vma, addr);
>  			else
> -- 
> 1.7.3.2
> 
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