* [PATCH 1/4] Figure Storage Hazard-Pointer Storage and Erasure: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
2017-06-10 14:28 [PATCH 0/4] Update on Chapter Deferred Processing Junchang Wang
@ 2017-06-10 14:28 ` Junchang Wang
2017-06-10 14:28 ` [PATCH 2/4] route_hazptr: " Junchang Wang
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Junchang Wang @ 2017-06-10 14:28 UTC (permalink / raw)
To: perfbook, paulmck; +Cc: Junchang Wang
Signed-off-by: Junchang Wang <junchangwang@gmail.com>
---
defer/hazptr.tex | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/defer/hazptr.tex b/defer/hazptr.tex
index cdde323..10ae7a1 100644
--- a/defer/hazptr.tex
+++ b/defer/hazptr.tex
@@ -26,12 +26,12 @@ may safely be freed.
2 {
3 void *tmp;
4
- 5 tmp = ACCESS_ONCE(*p);
- 6 ACCESS_ONCE(*hp) = tmp;
+ 5 tmp = READ_ONCE(*p);
+ 6 WRITE_ONCE(*hp, tmp);
7 smp_mb();
- 8 if (tmp != ACCESS_ONCE(*p) ||
+ 8 if (tmp != READ_ONCE(*p) ||
9 tmp == HAZPTR_POISON) {
-10 ACCESS_ONCE(*hp) = NULL;
+10 WRITE_ONCE(*hp, NULL);
11 return 0;
12 }
13 return 1;
@@ -40,7 +40,7 @@ may safely be freed.
16 void hp_erase(void **hp)
17 {
18 smp_mb();
-19 ACCESS_ONCE(*hp) = NULL;
+19 WRITE_ONCE(*hp, NULL);
20 hp_free(hp);
21 }
\end{verbbox}
--
2.7.4
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 2/4] route_hazptr: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
2017-06-10 14:28 [PATCH 0/4] Update on Chapter Deferred Processing Junchang Wang
2017-06-10 14:28 ` [PATCH 1/4] Figure Storage Hazard-Pointer Storage and Erasure: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE() Junchang Wang
@ 2017-06-10 14:28 ` Junchang Wang
2017-06-10 14:28 ` [PATCH 3/4] route_seqlock: " Junchang Wang
2017-06-10 14:35 ` [PATCH 0/4] Update on Chapter Deferred Processing Junchang Wang
3 siblings, 0 replies; 6+ messages in thread
From: Junchang Wang @ 2017-06-10 14:28 UTC (permalink / raw)
To: perfbook, paulmck; +Cc: Junchang Wang
Signed-off-by: Junchang Wang <junchangwang@gmail.com>
---
CodeSamples/defer/route_hazptr.c | 10 +++++-----
defer/hazptr.tex | 6 +++---
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/CodeSamples/defer/route_hazptr.c b/CodeSamples/defer/route_hazptr.c
index 590ba4d..49e6e4a 100644
--- a/CodeSamples/defer/route_hazptr.c
+++ b/CodeSamples/defer/route_hazptr.c
@@ -49,7 +49,7 @@ unsigned long route_lookup(unsigned long addr)
retry:
repp = &route_list.re_next;
do {
- rep = ACCESS_ONCE(*repp);
+ rep = READ_ONCE(*repp);
if (rep == NULL)
return ULONG_MAX;
if (rep == (struct route_entry *)HAZPTR_POISON)
@@ -61,13 +61,13 @@ retry:
smp_mb(); /* Force pointer loads in order. */
/* Recheck the hazard pointer against the original. */
- if (ACCESS_ONCE(*repp) != rep)
+ if (READ_ONCE(*repp) != rep)
goto retry;
/* Advance to next. */
repp = &rep->re_next;
} while (rep->addr != addr);
- if (ACCESS_ONCE(rep->re_freed))
+ if (READ_ONCE(rep->re_freed))
abort();
return rep->iface;
}
@@ -129,7 +129,7 @@ void route_clear(void)
spin_lock(&routelock);
rep = route_list.re_next;
- ACCESS_ONCE(route_list.re_next) = NULL;
+ WRITE_ONCE(route_list.re_next, NULL);
while (rep != NULL) {
rep1 = rep->re_next;
rep->re_next = (struct route_entry *)HAZPTR_POISON;
@@ -157,7 +157,7 @@ void hazptr_free(void *p)
{
struct route_entry *rep = p;
- ACCESS_ONCE(rep->re_freed) = 1;
+ WRITE_ONCE(rep->re_freed, 1);
free(p);
}
diff --git a/defer/hazptr.tex b/defer/hazptr.tex
index 10ae7a1..b45f5b6 100644
--- a/defer/hazptr.tex
+++ b/defer/hazptr.tex
@@ -201,7 +201,7 @@ and in other publications~\cite{ThomasEHart2007a,McKenney:2013:SDS:2483852.24838
18 retry:
19 repp = &route_list.re_next;
20 do {
-21 rep = ACCESS_ONCE(*repp);
+21 rep = READ_ONCE(*repp);
22 if (rep == NULL)
23 return ULONG_MAX;
24 if (rep == (struct route_entry *)HAZPTR_POISON)
@@ -209,11 +209,11 @@ and in other publications~\cite{ThomasEHart2007a,McKenney:2013:SDS:2483852.24838
26 my_hazptr[offset].p = &rep->hh;
27 offset = !offset;
28 smp_mb();
-29 if (ACCESS_ONCE(*repp) != rep)
+29 if (READ_ONCE(*repp) != rep)
30 goto retry;
31 repp = &rep->re_next;
32 } while (rep->addr != addr);
-33 if (ACCESS_ONCE(rep->re_freed))
+33 if (READ_ONCE(rep->re_freed))
34 abort();
35 return rep->iface;
36 }
--
2.7.4
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 3/4] route_seqlock: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
2017-06-10 14:28 [PATCH 0/4] Update on Chapter Deferred Processing Junchang Wang
2017-06-10 14:28 ` [PATCH 1/4] Figure Storage Hazard-Pointer Storage and Erasure: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE() Junchang Wang
2017-06-10 14:28 ` [PATCH 2/4] route_hazptr: " Junchang Wang
@ 2017-06-10 14:28 ` Junchang Wang
2017-06-10 14:35 ` [PATCH 0/4] Update on Chapter Deferred Processing Junchang Wang
3 siblings, 0 replies; 6+ messages in thread
From: Junchang Wang @ 2017-06-10 14:28 UTC (permalink / raw)
To: perfbook, paulmck; +Cc: Junchang Wang
Signed-off-by: Junchang Wang <junchangwang@gmail.com>
---
CodeSamples/defer/route_seqlock.c | 6 +++---
CodeSamples/defer/seqlock.h | 4 ++--
defer/seqlock.tex | 12 ++++++------
3 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/CodeSamples/defer/route_seqlock.c b/CodeSamples/defer/route_seqlock.c
index 633cf05..8224682 100644
--- a/CodeSamples/defer/route_seqlock.c
+++ b/CodeSamples/defer/route_seqlock.c
@@ -47,7 +47,7 @@ retry:
s = read_seqbegin(&sl);
repp = &route_list.re_next;
do {
- rep = ACCESS_ONCE(*repp);
+ rep = READ_ONCE(*repp);
if (rep == NULL) {
if (read_seqretry(&sl, s))
goto retry;
@@ -57,7 +57,7 @@ retry:
/* Advance to next. */
repp = &rep->re_next;
} while (rep->addr != addr);
- if (ACCESS_ONCE(rep->re_freed))
+ if (READ_ONCE(rep->re_freed))
abort();
ret = rep->iface;
if (read_seqretry(&sl, s))
@@ -123,7 +123,7 @@ void route_clear(void)
write_seqlock(&sl);
rep = route_list.re_next;
- ACCESS_ONCE(route_list.re_next) = NULL;
+ WRITE_ONCE(route_list.re_next, NULL);
while (rep != NULL) {
rep1 = rep->re_next;
free(rep);
diff --git a/CodeSamples/defer/seqlock.h b/CodeSamples/defer/seqlock.h
index b210944..c994285 100644
--- a/CodeSamples/defer/seqlock.h
+++ b/CodeSamples/defer/seqlock.h
@@ -38,7 +38,7 @@ static inline unsigned long read_seqbegin(seqlock_t *slp)
{
unsigned long s;
- s = ACCESS_ONCE(slp->seq);
+ s = READ_ONCE(slp->seq);
smp_mb();
return s & ~0x1UL;
}
@@ -48,7 +48,7 @@ static inline int read_seqretry(seqlock_t *slp, unsigned long oldseq)
unsigned long s;
smp_mb();
- s = ACCESS_ONCE(slp->seq);
+ s = READ_ONCE(slp->seq);
return s != oldseq;
}
diff --git a/defer/seqlock.tex b/defer/seqlock.tex
index ba8abfe..cb5e4e6 100644
--- a/defer/seqlock.tex
+++ b/defer/seqlock.tex
@@ -116,7 +116,7 @@ It is also used in pathname traversal to detect concurrent rename operations.
13 {
14 unsigned long s;
15
-16 s = ACCESS_ONCE(slp->seq);
+16 s = READ_ONCE(slp->seq);
17 smp_mb();
18 return s & ~0x1UL;
19 }
@@ -127,7 +127,7 @@ It is also used in pathname traversal to detect concurrent rename operations.
24 unsigned long s;
25
26 smp_mb();
-27 s = ACCESS_ONCE(slp->seq);
+27 s = READ_ONCE(slp->seq);
28 return s != oldseq;
29 }
30
@@ -211,11 +211,11 @@ in other words, that there has been no writer, and returns true if so.
In older versions of the Linux kernel, no.
In very new versions of the Linux kernel, line~16 could use
- \co{smp_load_acquire()} instead of \co{ACCESS_ONCE()}, which
+ \co{smp_load_acquire()} instead of \co{READ_ONCE()}, which
in turn would allow the \co{smp_mb()} on line~17 to be dropped.
Similarly, line~41 could use an \co{smp_store_release()}, for
example, as follows: \\
- \co{smp_store_release(&slp->seq, ACCESS_ONCE(slp->seq) + 1);} \\
+ \co{smp_store_release(&slp->seq, READ_ONCE(slp->seq) + 1);} \\
This would allow the \co{smp_mb()} on line~40 to be dropped.
} \QuickQuizEnd
@@ -310,7 +310,7 @@ increment of the sequence number on line~44, then releases the lock.
18 s = read_seqbegin(&sl);
19 repp = &route_list.re_next;
20 do {
-21 rep = ACCESS_ONCE(*repp);
+21 rep = READ_ONCE(*repp);
22 if (rep == NULL) {
23 if (read_seqretry(&sl, s))
24 goto retry;
@@ -318,7 +318,7 @@ increment of the sequence number on line~44, then releases the lock.
26 }
27 repp = &rep->re_next;
28 } while (rep->addr != addr);
-29 if (ACCESS_ONCE(rep->re_freed))
+29 if (READ_ONCE(rep->re_freed))
30 abort();
31 ret = rep->iface;
32 if (read_seqretry(&sl, s))
--
2.7.4
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH 0/4] Update on Chapter Deferred Processing
2017-06-10 14:28 [PATCH 0/4] Update on Chapter Deferred Processing Junchang Wang
` (2 preceding siblings ...)
2017-06-10 14:28 ` [PATCH 3/4] route_seqlock: " Junchang Wang
@ 2017-06-10 14:35 ` Junchang Wang
2017-06-10 17:08 ` Paul E. McKenney
3 siblings, 1 reply; 6+ messages in thread
From: Junchang Wang @ 2017-06-10 14:35 UTC (permalink / raw)
To: perfbook, Paul E. McKenney
Hi Paul,
The fourth patch is a false alarm. So I won't send it out. Please
review and apply patches 1 - 3. Thanks.
--Jason
On Sat, Jun 10, 2017 at 10:28 PM, Junchang Wang <junchangwang@gmail.com> wrote:
> Hi Paul,
>
> I'm reading Chapter Deferred Processing, and following are some patches. Please
> take a look.
>
> --Jason
>
> Junchang Wang (4):
> Figure Storage Hazard-Pointer Storage and Erasure: Switch from
> ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
> route_hazptr: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
> route_seqlock: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
>
> CodeSamples/defer/route_hazptr.c | 10 +++++-----
> CodeSamples/defer/route_seqlock.c | 6 +++---
> CodeSamples/defer/seqlock.h | 4 ++--
> defer/hazptr.tex | 16 ++++++++--------
> defer/seqlock.tex | 12 ++++++------
> 5 files changed, 26 insertions(+), 26 deletions(-)
>
> --
> 2.7.4
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 0/4] Update on Chapter Deferred Processing
2017-06-10 14:35 ` [PATCH 0/4] Update on Chapter Deferred Processing Junchang Wang
@ 2017-06-10 17:08 ` Paul E. McKenney
0 siblings, 0 replies; 6+ messages in thread
From: Paul E. McKenney @ 2017-06-10 17:08 UTC (permalink / raw)
To: Junchang Wang; +Cc: perfbook
On Sat, Jun 10, 2017 at 10:35:25PM +0800, Junchang Wang wrote:
> Hi Paul,
>
> The fourth patch is a false alarm. So I won't send it out. Please
> review and apply patches 1 - 3. Thanks.
Applied and pushed, thank you!
Please see note below.
> --Jason
>
> On Sat, Jun 10, 2017 at 10:28 PM, Junchang Wang <junchangwang@gmail.com> wrote:
> > Hi Paul,
> >
> > I'm reading Chapter Deferred Processing, and following are some patches. Please
> > take a look.
> >
> > --Jason
> >
> > Junchang Wang (4):
> > Figure Storage Hazard-Pointer Storage and Erasure: Switch from
> > ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
When changing text, it suffices to give the chapter's top-level
directory name, so I changed this to:
defer: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
> > route_hazptr: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
> > route_seqlock: Switch from ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
These are fine, giving the name of the executable for changes to a
given code sample is quite good, thank you!
Thanx, Paul
> > CodeSamples/defer/route_hazptr.c | 10 +++++-----
> > CodeSamples/defer/route_seqlock.c | 6 +++---
> > CodeSamples/defer/seqlock.h | 4 ++--
> > defer/hazptr.tex | 16 ++++++++--------
> > defer/seqlock.tex | 12 ++++++------
> > 5 files changed, 26 insertions(+), 26 deletions(-)
> >
> > --
> > 2.7.4
> >
>
^ permalink raw reply [flat|nested] 6+ messages in thread