Message ID | 20090624162112.GB5409@jolsa.lab.eng.brq.redhat.com |
---|---|
State | RFC, archived |
Delegated to: | David Miller |
Headers | show |
On 06/24, Jiri Olsa wrote: > > +/* The read_lock() on x86 is a full memory barrier. */ > +#define smp_mb__after_read_lock() barrier() Just curious, why do we need barrier() ? I must admit, personally I dislike _read_lock part. Because I think we need a "more generic" smp_mb__{before,after}_lock() or whatever which work for spin_lock/read_lock/write_lock. In that case it can have more users. Btw, in fs/select.c too, see __pollwake(). And surprise, > --- a/fs/select.c > +++ b/fs/select.c > @@ -219,6 +219,10 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, > init_waitqueue_func_entry(&entry->wait, pollwake); > entry->wait.private = pwq; > add_wait_queue(wait_address, &entry->wait); > + > + /* This memory barrier is paired with the smp_mb__after_read_lock > + * in the sk_has_sleeper. */ > + smp_mb(); This could be smp_mb__after_lock() too. Oleg. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 06/24, Oleg Nesterov wrote: > > On 06/24, Jiri Olsa wrote: > > > > +/* The read_lock() on x86 is a full memory barrier. */ > > +#define smp_mb__after_read_lock() barrier() > > Just curious, why do we need barrier() ? > > I must admit, personally I dislike _read_lock part. Because I think we > need a "more generic" smp_mb__{before,after}_lock() or whatever which > work for spin_lock/read_lock/write_lock. > > In that case it can have more users. Btw, in fs/select.c too, see > __pollwake(). > > And surprise, > > > --- a/fs/select.c > > +++ b/fs/select.c > > @@ -219,6 +219,10 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, > > init_waitqueue_func_entry(&entry->wait, pollwake); > > entry->wait.private = pwq; > > add_wait_queue(wait_address, &entry->wait); > > + > > + /* This memory barrier is paired with the smp_mb__after_read_lock > > + * in the sk_has_sleeper. */ > > + smp_mb(); > > This could be smp_mb__after_lock() too. Cough. this needs mb__after_UNlock(), sorry. Oleg. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Jiri Olsa a écrit : > > I made the modification, plz check the attached diff. > > I found some places where the read_lock is not ahead of the check: > "if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))" > > I'm not sure we dont want to address those as well; located in following > files: > drivers/net/tun.c > net/core/stream.c > net/sctp/socket.c > net/sunrpc/svcsock.c We'll take care of them later :) > > > thanks, > jirka > This patch is OK with me, please submit a new formal patch with fresh ChangeLog so that we can all agree and Signed-off-by/Acked-by Oleg, I think your comment can be addressed in a followup patch ? Thanks to all > > diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h > index b7e5db8..570c0ff 100644 > --- a/arch/x86/include/asm/spinlock.h > +++ b/arch/x86/include/asm/spinlock.h > @@ -302,4 +302,7 @@ static inline void __raw_write_unlock(raw_rwlock_t *rw) > #define _raw_read_relax(lock) cpu_relax() > #define _raw_write_relax(lock) cpu_relax() > > +/* The read_lock() on x86 is a full memory barrier. */ > +#define smp_mb__after_read_lock() barrier() > + > #endif /* _ASM_X86_SPINLOCK_H */ > diff --git a/fs/select.c b/fs/select.c > index d870237..cf5d80b 100644 > --- a/fs/select.c > +++ b/fs/select.c > @@ -219,6 +219,10 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, > init_waitqueue_func_entry(&entry->wait, pollwake); > entry->wait.private = pwq; > add_wait_queue(wait_address, &entry->wait); > + > + /* This memory barrier is paired with the smp_mb__after_read_lock > + * in the sk_has_sleeper. */ > + smp_mb(); > } > > int poll_schedule_timeout(struct poll_wqueues *pwq, int state, > diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h > index 252b245..dd28726 100644 > --- a/include/linux/spinlock.h > +++ b/include/linux/spinlock.h > @@ -132,6 +132,11 @@ do { \ > #endif /*__raw_spin_is_contended*/ > #endif > > +/* The read_lock does not imply full memory barrier. */ > +#ifndef smp_mb__after_read_lock > +#define smp_mb__after_read_lock() smp_mb() > +#endif > + > /** > * spin_unlock_wait - wait until the spinlock gets unlocked > * @lock: the spinlock in question. > diff --git a/include/net/sock.h b/include/net/sock.h > index 07133c5..a02a956 100644 > --- a/include/net/sock.h > +++ b/include/net/sock.h > @@ -1241,6 +1241,24 @@ static inline int sk_has_allocations(const struct sock *sk) > return sk_wmem_alloc_get(sk) || sk_rmem_alloc_get(sk); > } > > +/** > + * sk_has_sleeper - check if there are any waiting processes > + * @sk: socket > + * > + * Returns true if socket has waiting processes > + */ > +static inline int sk_has_sleeper(struct sock *sk) > +{ > + /* > + * We need to be sure we are in sync with the > + * add_wait_queue modifications to the wait queue. > + * > + * This memory barrier is paired in the __pollwait. > + */ > + smp_mb__after_read_lock(); > + return sk->sk_sleep && waitqueue_active(sk->sk_sleep); > +} > + > /* > * Queue a received datagram if it will fit. Stream and sequenced > * protocols can't normally use this as they need to fit buffers in > diff --git a/net/atm/common.c b/net/atm/common.c > index c1c9793..67a8642 100644 > --- a/net/atm/common.c > +++ b/net/atm/common.c > @@ -92,7 +92,7 @@ static void vcc_sock_destruct(struct sock *sk) > static void vcc_def_wakeup(struct sock *sk) > { > read_lock(&sk->sk_callback_lock); > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up(sk->sk_sleep); > read_unlock(&sk->sk_callback_lock); > } > @@ -110,7 +110,7 @@ static void vcc_write_space(struct sock *sk) > read_lock(&sk->sk_callback_lock); > > if (vcc_writable(sk)) { > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up_interruptible(sk->sk_sleep); > > sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); > diff --git a/net/core/sock.c b/net/core/sock.c > index b0ba569..6354863 100644 > --- a/net/core/sock.c > +++ b/net/core/sock.c > @@ -1715,7 +1715,7 @@ EXPORT_SYMBOL(sock_no_sendpage); > static void sock_def_wakeup(struct sock *sk) > { > read_lock(&sk->sk_callback_lock); > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up_interruptible_all(sk->sk_sleep); > read_unlock(&sk->sk_callback_lock); > } > @@ -1723,7 +1723,7 @@ static void sock_def_wakeup(struct sock *sk) > static void sock_def_error_report(struct sock *sk) > { > read_lock(&sk->sk_callback_lock); > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up_interruptible_poll(sk->sk_sleep, POLLERR); > sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR); > read_unlock(&sk->sk_callback_lock); > @@ -1732,7 +1732,7 @@ static void sock_def_error_report(struct sock *sk) > static void sock_def_readable(struct sock *sk, int len) > { > read_lock(&sk->sk_callback_lock); > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up_interruptible_sync_poll(sk->sk_sleep, POLLIN | > POLLRDNORM | POLLRDBAND); > sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); > @@ -1747,7 +1747,7 @@ static void sock_def_write_space(struct sock *sk) > * progress. --DaveM > */ > if ((atomic_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf) { > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up_interruptible_sync_poll(sk->sk_sleep, POLLOUT | > POLLWRNORM | POLLWRBAND); > > diff --git a/net/dccp/output.c b/net/dccp/output.c > index c0e88c1..c96119f 100644 > --- a/net/dccp/output.c > +++ b/net/dccp/output.c > @@ -196,7 +196,7 @@ void dccp_write_space(struct sock *sk) > { > read_lock(&sk->sk_callback_lock); > > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up_interruptible(sk->sk_sleep); > /* Should agree with poll, otherwise some programs break */ > if (sock_writeable(sk)) > diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c > index 6be5f92..ba0149d 100644 > --- a/net/iucv/af_iucv.c > +++ b/net/iucv/af_iucv.c > @@ -306,7 +306,7 @@ static inline int iucv_below_msglim(struct sock *sk) > static void iucv_sock_wake_msglim(struct sock *sk) > { > read_lock(&sk->sk_callback_lock); > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up_interruptible_all(sk->sk_sleep); > sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); > read_unlock(&sk->sk_callback_lock); > diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c > index eac5e7b..60e0e38 100644 > --- a/net/rxrpc/af_rxrpc.c > +++ b/net/rxrpc/af_rxrpc.c > @@ -63,7 +63,7 @@ static void rxrpc_write_space(struct sock *sk) > _enter("%p", sk); > read_lock(&sk->sk_callback_lock); > if (rxrpc_writable(sk)) { > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up_interruptible(sk->sk_sleep); > sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); > } > diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c > index 36d4e44..143143a 100644 > --- a/net/unix/af_unix.c > +++ b/net/unix/af_unix.c > @@ -315,7 +315,7 @@ static void unix_write_space(struct sock *sk) > { > read_lock(&sk->sk_callback_lock); > if (unix_writable(sk)) { > - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) > + if (sk_has_sleeper(sk)) > wake_up_interruptible_sync(sk->sk_sleep); > sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); > } > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Eric Dumazet a écrit : > Jiri Olsa a écrit : >> I made the modification, plz check the attached diff. >> >> I found some places where the read_lock is not ahead of the check: >> "if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))" >> >> I'm not sure we dont want to address those as well; located in following >> files: >> drivers/net/tun.c >> net/core/stream.c >> net/sctp/socket.c >> net/sunrpc/svcsock.c > > We'll take care of them later :) > >> >> thanks, >> jirka >> > > This patch is OK with me, please submit a new formal patch with > fresh ChangeLog so that we can all agree and Signed-off-by/Acked-by > > Oleg, I think your comment can be addressed in a followup patch ? > > Thanks to all To clarify, I meant the second comment from Oleg. Jiri, please define a "smp_mb__after_lock()" instead of smp_mb__after_read_lock() +/* The {read|write|spin}_lock() on x86 are full memory barriers. */ +#define smp_mb__after_lock() do { } while (0) + -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Oleg Nesterov a écrit : > On 06/24, Oleg Nesterov wrote: >> On 06/24, Jiri Olsa wrote: >>> +/* The read_lock() on x86 is a full memory barrier. */ >>> +#define smp_mb__after_read_lock() barrier() >> Just curious, why do we need barrier() ? >> >> I must admit, personally I dislike _read_lock part. Because I think we >> need a "more generic" smp_mb__{before,after}_lock() or whatever which >> work for spin_lock/read_lock/write_lock. >> >> In that case it can have more users. Btw, in fs/select.c too, see >> __pollwake(). >> >> And surprise, >> >>> --- a/fs/select.c >>> +++ b/fs/select.c >>> @@ -219,6 +219,10 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, >>> init_waitqueue_func_entry(&entry->wait, pollwake); >>> entry->wait.private = pwq; >>> add_wait_queue(wait_address, &entry->wait); >>> + >>> + /* This memory barrier is paired with the smp_mb__after_read_lock >>> + * in the sk_has_sleeper. */ >>> + smp_mb(); >> This could be smp_mb__after_lock() too. > > Cough. this needs mb__after_UNlock(), sorry. > Yes, and this time you need separate smp_mb__after_spin_unlock(), as rwlocks and spinlocks dont have same unlock implementation. (spin_unlock dont have memory barrier on x86, while read_write_unlock do have a barrier) As it wont give us a benefit on x86 but code obfuscation, I suspect we can leave this for now :) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index b7e5db8..570c0ff 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -302,4 +302,7 @@ static inline void __raw_write_unlock(raw_rwlock_t *rw) #define _raw_read_relax(lock) cpu_relax() #define _raw_write_relax(lock) cpu_relax() +/* The read_lock() on x86 is a full memory barrier. */ +#define smp_mb__after_read_lock() barrier() + #endif /* _ASM_X86_SPINLOCK_H */ diff --git a/fs/select.c b/fs/select.c index d870237..cf5d80b 100644 --- a/fs/select.c +++ b/fs/select.c @@ -219,6 +219,10 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, init_waitqueue_func_entry(&entry->wait, pollwake); entry->wait.private = pwq; add_wait_queue(wait_address, &entry->wait); + + /* This memory barrier is paired with the smp_mb__after_read_lock + * in the sk_has_sleeper. */ + smp_mb(); } int poll_schedule_timeout(struct poll_wqueues *pwq, int state, diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 252b245..dd28726 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -132,6 +132,11 @@ do { \ #endif /*__raw_spin_is_contended*/ #endif +/* The read_lock does not imply full memory barrier. */ +#ifndef smp_mb__after_read_lock +#define smp_mb__after_read_lock() smp_mb() +#endif + /** * spin_unlock_wait - wait until the spinlock gets unlocked * @lock: the spinlock in question. diff --git a/include/net/sock.h b/include/net/sock.h index 07133c5..a02a956 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1241,6 +1241,24 @@ static inline int sk_has_allocations(const struct sock *sk) return sk_wmem_alloc_get(sk) || sk_rmem_alloc_get(sk); } +/** + * sk_has_sleeper - check if there are any waiting processes + * @sk: socket + * + * Returns true if socket has waiting processes + */ +static inline int sk_has_sleeper(struct sock *sk) +{ + /* + * We need to be sure we are in sync with the + * add_wait_queue modifications to the wait queue. + * + * This memory barrier is paired in the __pollwait. + */ + smp_mb__after_read_lock(); + return sk->sk_sleep && waitqueue_active(sk->sk_sleep); +} + /* * Queue a received datagram if it will fit. Stream and sequenced * protocols can't normally use this as they need to fit buffers in diff --git a/net/atm/common.c b/net/atm/common.c index c1c9793..67a8642 100644 --- a/net/atm/common.c +++ b/net/atm/common.c @@ -92,7 +92,7 @@ static void vcc_sock_destruct(struct sock *sk) static void vcc_def_wakeup(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up(sk->sk_sleep); read_unlock(&sk->sk_callback_lock); } @@ -110,7 +110,7 @@ static void vcc_write_space(struct sock *sk) read_lock(&sk->sk_callback_lock); if (vcc_writable(sk)) { - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible(sk->sk_sleep); sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); diff --git a/net/core/sock.c b/net/core/sock.c index b0ba569..6354863 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1715,7 +1715,7 @@ EXPORT_SYMBOL(sock_no_sendpage); static void sock_def_wakeup(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_all(sk->sk_sleep); read_unlock(&sk->sk_callback_lock); } @@ -1723,7 +1723,7 @@ static void sock_def_wakeup(struct sock *sk) static void sock_def_error_report(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_poll(sk->sk_sleep, POLLERR); sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR); read_unlock(&sk->sk_callback_lock); @@ -1732,7 +1732,7 @@ static void sock_def_error_report(struct sock *sk) static void sock_def_readable(struct sock *sk, int len) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_sync_poll(sk->sk_sleep, POLLIN | POLLRDNORM | POLLRDBAND); sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); @@ -1747,7 +1747,7 @@ static void sock_def_write_space(struct sock *sk) * progress. --DaveM */ if ((atomic_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf) { - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_sync_poll(sk->sk_sleep, POLLOUT | POLLWRNORM | POLLWRBAND); diff --git a/net/dccp/output.c b/net/dccp/output.c index c0e88c1..c96119f 100644 --- a/net/dccp/output.c +++ b/net/dccp/output.c @@ -196,7 +196,7 @@ void dccp_write_space(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible(sk->sk_sleep); /* Should agree with poll, otherwise some programs break */ if (sock_writeable(sk)) diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c index 6be5f92..ba0149d 100644 --- a/net/iucv/af_iucv.c +++ b/net/iucv/af_iucv.c @@ -306,7 +306,7 @@ static inline int iucv_below_msglim(struct sock *sk) static void iucv_sock_wake_msglim(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_all(sk->sk_sleep); sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); read_unlock(&sk->sk_callback_lock); diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c index eac5e7b..60e0e38 100644 --- a/net/rxrpc/af_rxrpc.c +++ b/net/rxrpc/af_rxrpc.c @@ -63,7 +63,7 @@ static void rxrpc_write_space(struct sock *sk) _enter("%p", sk); read_lock(&sk->sk_callback_lock); if (rxrpc_writable(sk)) { - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible(sk->sk_sleep); sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); } diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 36d4e44..143143a 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -315,7 +315,7 @@ static void unix_write_space(struct sock *sk) { read_lock(&sk->sk_callback_lock); if (unix_writable(sk)) { - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_sync(sk->sk_sleep); sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); }