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Jiri Olsa a57de0b433 net: adding memory barrier to the poll and receive callbacks ... Adding memory barrier after the poll_wait function, paired with receive callbacks. Adding fuctions sock_poll_wait and sk_has_sleeper to wrap the memory barrier. Without the memory barrier, following race can happen. The race fires, when following code paths meet, and the tp->rcv_nxt and __add_wait_queue updates stay in CPU caches. CPU1 CPU2 sys_select receive packet ... ... __add_wait_queue update tp->rcv_nxt ... ... tp->rcv_nxt check sock_def_readable ... { schedule ... if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) wake_up_interruptible(sk->sk_sleep) ... } If there was no cache the code would work ok, since the wait_queue and rcv_nxt are opposit to each other. Meaning that once tp->rcv_nxt is updated by CPU2, the CPU1 either already passed the tp->rcv_nxt check and sleeps, or will get the new value for tp->rcv_nxt and will return with new data mask. In both cases the process (CPU1) is being added to the wait queue, so the waitqueue_active (CPU2) call cannot miss and will wake up CPU1. The bad case is when the __add_wait_queue changes done by CPU1 stay in its cache, and so does the tp->rcv_nxt update on CPU2 side. The CPU1 will then endup calling schedule and sleep forever if there are no more data on the socket. Calls to poll_wait in following modules were ommited: net/bluetooth/af_bluetooth.c net/irda/af_irda.c net/irda/irnet/irnet_ppp.c net/mac80211/rc80211_pid_debugfs.c net/phonet/socket.c net/rds/af_rds.c net/rfkill/core.c net/sunrpc/cache.c net/sunrpc/rpc_pipe.c net/tipc/socket.c Signed-off-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>		16 years ago
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ccids	dccp ccid-3: Fix RFC reference	16 years ago
Kconfig	…
Makefile	dccp: Integrate the TFRC library with DCCP	16 years ago
ackvec.c	…
ackvec.h	dccp: Minimise header option overhead in setting the MPS	16 years ago
ccid.c	dccp: Integrate the TFRC library with DCCP	16 years ago
ccid.h	…
dccp.h	dccp: Do not let initial option overhead shrink the MPS	16 years ago
diag.c	…
feat.c	dccp: Debugging functions for feature negotiation	16 years ago
feat.h	dccp: Debugging functions for feature negotiation	16 years ago
input.c	dccp: Integrate the TFRC library with DCCP	16 years ago
ipv4.c	net: skb->dst accessors	16 years ago
ipv6.c	ipv6: Use correct data types for ICMPv6 type and code	16 years ago
ipv6.h	…
minisocks.c	dccp: Implement both feature-local and feature-remote Sequence Window feature	16 years ago
options.c	dccp: Debugging functions for feature negotiation	16 years ago
output.c	net: adding memory barrier to the poll and receive callbacks	16 years ago
probe.c	…
proto.c	net: adding memory barrier to the poll and receive callbacks	16 years ago
sysctl.c	dccp: Initialisation and type-checking of feature sysctls	16 years ago
timer.c	…