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Groups > linux.kernel > #1646229 > unrolled thread
| Started by | Wei Yongjun <weiyj.lk@gmail.com> |
|---|---|
| First post | 2017-05-21 02:50 +0200 |
| Last post | 2017-05-22 20:50 +0200 |
| Articles | 4 — 3 participants |
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[PATCH] goldfish_pipe: use GFP_ATOMIC under spin lock Wei Yongjun <weiyj.lk@gmail.com> - 2017-05-21 02:50 +0200
Re: [PATCH] goldfish_pipe: use GFP_ATOMIC under spin lock Michal Hocko <mhocko@kernel.org> - 2017-05-21 09:50 +0200
Re: [PATCH] goldfish_pipe: use GFP_ATOMIC under spin lock Michal Hocko <mhocko@kernel.org> - 2017-05-22 14:00 +0200
Re: [PATCH] goldfish_pipe: use GFP_ATOMIC under spin lock Alan Cox <gnomes@lxorguk.ukuu.org.uk> - 2017-05-22 20:50 +0200
| From | Wei Yongjun <weiyj.lk@gmail.com> |
|---|---|
| Date | 2017-05-21 02:50 +0200 |
| Subject | [PATCH] goldfish_pipe: use GFP_ATOMIC under spin lock |
| Message-ID | <tJneh-kw-3@gated-at.bofh.it> |
From: Wei Yongjun <weiyongjun1@huawei.com> The function get_free_pipe_id_locked() is called from goldfish_pipe_open() with a lock is held, so we should use GFP_ATOMIC instead of GFP_KERNEL. Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com> --- drivers/platform/goldfish/goldfish_pipe.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c index 2de1e60..5f36721 100644 --- a/drivers/platform/goldfish/goldfish_pipe.c +++ b/drivers/platform/goldfish/goldfish_pipe.c @@ -704,7 +704,7 @@ static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev) /* Reallocate the array */ u32 new_capacity = 2 * dev->pipes_capacity; struct goldfish_pipe **pipes = - kcalloc(new_capacity, sizeof(*pipes), GFP_KERNEL); + kcalloc(new_capacity, sizeof(*pipes), GFP_ATOMIC); if (!pipes) return -ENOMEM; memcpy(pipes, dev->pipes, sizeof(*pipes) * dev->pipes_capacity);
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| From | Michal Hocko <mhocko@kernel.org> |
|---|---|
| Date | 2017-05-21 09:50 +0200 |
| Message-ID | <tJtMJ-4Tk-9@gated-at.bofh.it> |
| In reply to | #1646229 |
On Sun 21-05-17 00:45:46, Wei Yongjun wrote: > From: Wei Yongjun <weiyongjun1@huawei.com> > > The function get_free_pipe_id_locked() is called from > goldfish_pipe_open() with a lock is held, so we should > use GFP_ATOMIC instead of GFP_KERNEL. Why is GFP_NOWAIT insufficient? Does this path needs an access to memory reserves? > Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com> > --- > drivers/platform/goldfish/goldfish_pipe.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c > index 2de1e60..5f36721 100644 > --- a/drivers/platform/goldfish/goldfish_pipe.c > +++ b/drivers/platform/goldfish/goldfish_pipe.c > @@ -704,7 +704,7 @@ static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev) > /* Reallocate the array */ > u32 new_capacity = 2 * dev->pipes_capacity; > struct goldfish_pipe **pipes = > - kcalloc(new_capacity, sizeof(*pipes), GFP_KERNEL); > + kcalloc(new_capacity, sizeof(*pipes), GFP_ATOMIC); > if (!pipes) > return -ENOMEM; > memcpy(pipes, dev->pipes, sizeof(*pipes) * dev->pipes_capacity); > -- Michal Hocko SUSE Labs
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| From | Michal Hocko <mhocko@kernel.org> |
|---|---|
| Date | 2017-05-22 14:00 +0200 |
| Message-ID | <tJUad-5dJ-13@gated-at.bofh.it> |
| In reply to | #1646280 |
On Sun 21-05-17 09:48:36, Michal Hocko wrote: > On Sun 21-05-17 00:45:46, Wei Yongjun wrote: > > From: Wei Yongjun <weiyongjun1@huawei.com> > > > > The function get_free_pipe_id_locked() is called from > > goldfish_pipe_open() with a lock is held, so we should > > use GFP_ATOMIC instead of GFP_KERNEL. > > Why is GFP_NOWAIT insufficient? Does this path needs an access to memory > reserves? And now when looking at the code more deeply, wouldn't it be much better to simply do the allocation outside of the spin lock and do assignments with the lock held? > > > Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com> > > --- > > drivers/platform/goldfish/goldfish_pipe.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c > > index 2de1e60..5f36721 100644 > > --- a/drivers/platform/goldfish/goldfish_pipe.c > > +++ b/drivers/platform/goldfish/goldfish_pipe.c > > @@ -704,7 +704,7 @@ static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev) > > /* Reallocate the array */ > > u32 new_capacity = 2 * dev->pipes_capacity; > > struct goldfish_pipe **pipes = > > - kcalloc(new_capacity, sizeof(*pipes), GFP_KERNEL); > > + kcalloc(new_capacity, sizeof(*pipes), GFP_ATOMIC); > > if (!pipes) > > return -ENOMEM; > > memcpy(pipes, dev->pipes, sizeof(*pipes) * dev->pipes_capacity); > > > > -- > Michal Hocko > SUSE Labs -- Michal Hocko SUSE Labs
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| From | Alan Cox <gnomes@lxorguk.ukuu.org.uk> |
|---|---|
| Date | 2017-05-22 20:50 +0200 |
| Message-ID | <tK0z0-NW-29@gated-at.bofh.it> |
| In reply to | #1646782 |
On Mon, 22 May 2017 13:51:52 +0200 Michal Hocko <mhocko@kernel.org> wrote: > On Sun 21-05-17 09:48:36, Michal Hocko wrote: > > On Sun 21-05-17 00:45:46, Wei Yongjun wrote: > > > From: Wei Yongjun <weiyongjun1@huawei.com> > > > > > > The function get_free_pipe_id_locked() is called from > > > goldfish_pipe_open() with a lock is held, so we should > > > use GFP_ATOMIC instead of GFP_KERNEL. > > > > Why is GFP_NOWAIT insufficient? Does this path needs an access to memory > > reserves? > > And now when looking at the code more deeply, wouldn't it be much better > to simply do the allocation outside of the spin lock and do assignments > with the lock held? That's far from trivial and certainly for backporting and an immediate fix this seems better. The allocations are not that large and any fail would be in open() not anywhere weird. Alan
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