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SubjectRe: [PATCH] cryptoapi: Fix sleeping
On Wed, Aug 13, 2003 at 09:03:23PM -0500, Matt Mackall wrote:
> On Wed, Aug 13, 2003 at 05:44:36PM -0700, Andrew Morton wrote:
> > Jeff Garzik <jgarzik@pobox.com> wrote:
> > >
> > > Matt Mackall wrote:
> > > > We need in_atomic() so that we can call from regions where preempt is
> > > > disabled, for instance when using per_cpu crypto tfms.
> > > >
> > > > diff -urN -X dontdiff orig/crypto/internal.h work/crypto/internal.h
> > > > +++ work/crypto/internal.h 2003-08-12 14:38:54.000000000 -0500
> > > > @@ -37,7 +37,7 @@
> > > >
> > > > static inline void crypto_yield(struct crypto_tfm *tfm)
> > > > {
> > > > - if (!in_softirq())
> > > > + if (!in_atomic())
> > > > cond_resched();
> > >
> > >
> > > Do you really want to schedule inside preempt_disable() ?
> > >
> >
> > in_atomic() returns false inside spin_lock() on non-preemptive kernels.
> >
> > Either this code needs to be removed altogether or it should be changed to
> >
> > BUG_ON(in_atomic());
> > cond_resched();
> >
> > and the callers should be fixed up.
>
> Cryptoapi probably needs a flag for skipping the yield. I'll look into it.

Ok, for reference, the code calling yield is stuff like this buried in
cryptoapi:

static void update(struct crypto_tfm *tfm,
struct scatterlist *sg, unsigned int nsg)
{
unsigned int i;

for (i = 0; i < nsg; i++) {
char *p = crypto_kmap(sg[i].page, 0) + sg[i].offset;
tfm->__crt_alg->cra_digest.dia_update(crypto_tfm_ctx(tfm),
p,
sg[i].length);
crypto_kunmap(p, 0);
crypto_yield(tfm);
}
}

It's basically trying to be friendly. Since we can't really detect
when it's safe to do such yields, we should be explicitly flag the
uses where its ok. Something like this:

diff -urN -X dontdiff orig/crypto/api.c work/crypto/api.c
--- orig/crypto/api.c 2003-07-13 22:38:38.000000000 -0500
+++ work/crypto/api.c 2003-08-14 01:53:07.000000000 -0500
@@ -53,7 +53,8 @@

static int crypto_init_flags(struct crypto_tfm *tfm, u32 flags)
{
- tfm->crt_flags = 0;
+ tfm->crt_flags = flags & CRYPTO_TFM_API_MASK;
+ flags &= ~CRYPTO_TFM_API_MASK;

switch (crypto_tfm_alg_type(tfm)) {
case CRYPTO_ALG_TYPE_CIPHER:
diff -urN -X dontdiff orig/crypto/internal.h work/crypto/internal.h
--- orig/crypto/internal.h 2003-07-13 22:29:11.000000000 -0500
+++ work/crypto/internal.h 2003-08-14 01:53:28.000000000 -0500
@@ -37,7 +37,7 @@

static inline void crypto_yield(struct crypto_tfm *tfm)
{
- if (!in_softirq())
+ if (tfm->crt_flags & CRYPTO_TFM_API_YIELD)
cond_resched();
}

diff -urN -X dontdiff orig/include/linux/crypto.h work/include/linux/crypto.h
--- orig/include/linux/crypto.h 2003-07-13 22:32:32.000000000 -0500
+++ work/include/linux/crypto.h 2003-08-14 01:53:07.000000000 -0500
@@ -36,7 +36,8 @@
*/
#define CRYPTO_TFM_MODE_MASK 0x000000ff
#define CRYPTO_TFM_REQ_MASK 0x000fff00
-#define CRYPTO_TFM_RES_MASK 0xfff00000
+#define CRYPTO_TFM_RES_MASK 0x7ff00000
+#define CRYPTO_TFM_API_MASK 0x80000000

#define CRYPTO_TFM_MODE_ECB 0x00000001
#define CRYPTO_TFM_MODE_CBC 0x00000002
@@ -50,6 +51,9 @@
#define CRYPTO_TFM_RES_BAD_BLOCK_LEN 0x00800000
#define CRYPTO_TFM_RES_BAD_FLAGS 0x01000000

+/* Allow for rescheduling after processing each sg element */
+#define CRYPTO_TFM_API_YIELD 0x80000000
+
/*
* Miscellaneous stuff.
*/
diff -urN -X dontdiff orig/include/linux/sched.h work/include/linux/sched.h
--- orig/include/linux/sched.h 2003-08-14 01:53:04.000000000 -0500
+++ work/include/linux/sched.h 2003-08-14 01:53:07.000000000 -0500
@@ -824,6 +824,7 @@
extern void __cond_resched(void);
static inline void cond_resched(void)
{
+ might_sleep();
if (need_resched())
__cond_resched();
}


--
Matt Mackall : http://www.selenic.com : of or relating to the moon
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