In order to reduce the number of poller updates, we can benefit from
the fact that modern pollers use sampling to report readiness and that
under load they rarely report the same FD multiple times in a row. As
such it's not always necessary to disable such FDs especially when we're
almost certain they'll be re-enabled again and will require another set
of syscalls.
Now instead of creating an update for a (possibly temporary) removal,
we only perform this removal if the FD is reported again as ready while
inactive. In addition this is performed via another update so that
alternating workloads like transfers have a chance to re-enable the
FD without any syscall during the loop (typically after the data that
filled a buffer have been sent). However we only do that for single-
threaded FDs as the other ones require a more complex setup and are not
on the critical path.
This does cause a few spurious wakeups but almost totally eliminates the
calls to epoll_ctl() on connections seeing intermitent traffic like HTTP/1
to a server or client.
A typical example with 100k requests for 4 kB objects over 200 connections
shows that the number of epoll_ctl() calls doesn't depend on the number
of requests anymore but most exclusively on the number of established
connections:
Before:
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
57.09 0.499964 0 654361 321190 recvfrom
38.33 0.335741 0 369097 1 epoll_wait
4.56 0.039898 0 44643 epoll_ctl
0.02 0.000211 1 200 200 connect
------ ----------- ----------- --------- --------- ----------------
100.00 0.875814 1068301 321391 total
After:
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
59.25 0.504676 0 657600 323630 recvfrom
40.68 0.346560 0 374289 1 epoll_wait
0.04 0.000370 0 620 epoll_ctl
0.03 0.000228 1 200 200 connect
------ ----------- ----------- --------- --------- ----------------
100.00 0.851834 1032709 323831 total
As expected there is also a slight increase of epoll_wait() calls since
delaying de-activation of events can occasionally cause one spurious
wakeup.
The cost of enabling polling in one direction with epoll is very high
because it requires one syscall per FD and per direction change. In
addition we don't know about input readiness until we either try to
receive() or enable polling and watch the result. With HTTP keep-alive,
both are equally expensive as it's very uncommon to see the server
instantly respond (unless it's a second stage of the same process on
localhost, which has become much less common with threads).
But when a connection is established it's also quite usual to have to
poll for sending (except on localhost or UNIX sockets where it almost
always instantly works). So this cost of polling could be factored out
with the second step if both were enabled together.
This is the idea behind this patch. What it does is to always enable
polling for Rx if it's not ready and at least one direction is active.
This means that if it's not explicitly disabled, or if it was but in a
state that causes the loss of the information (rx ready cannot be
guessed), then let's take any opportunity for a polling change to
enable it at the same time, and learn about rx readiness for free.
In addition the FD never gets unregistered for Rx unless it's ready
and was blocked (buffer full). This avoids a lot of the flip-flop
behaviour at beginning and end of requests.
On a test with 10k requests in keep-alive, the difference is quite
noticeable:
Before:
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
83.67 0.010847 0 20078 epoll_ctl
16.33 0.002117 0 2231 epoll_wait
0.00 0.000000 0 20 20 connect
------ ----------- ----------- --------- --------- ----------------
100.00 0.012964 22329 20 total
After:
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
96.35 0.003351 1 2644 epoll_wait
2.36 0.000082 4 20 20 connect
1.29 0.000045 0 66 epoll_ctl
------ ----------- ----------- --------- --------- ----------------
100.00 0.003478 2730 20 total
It may also save a recvfrom() after connect() by changing the following
sequence, effectively saving one epoll_ctl() and one recvfrom() :
before | after
-----------------------------+----------------------------
- connect() | - connect()
- epoll_ctl(add,out) | - epoll_ctl(add, in|out)
- sendto() | - epoll_wait() = out
- epoll_ctl(mod,in|out) | - send()
- epoll_wait() = out | - epoll_wait() = in|out
- recvfrom() = EAGAIN | - recvfrom() = OK
- epoll_ctl(mod,in) | - recvfrom() = EAGAIN
- epoll_wait() = in | - epoll_ctl(mod, in)
- recvfrom() = OK | - epoll_wait()
- recvfrom() = EAGAIN |
- epoll_wait() |
(...)
Now on a 10M req test on 16 threads with 2k concurrent conns and 415kreq/s,
we see 190k updates total and 14k epoll_ctl() only.
For now this almost never happens but with subsequent patches it will
become more important not to uselessly call the I/O handlers if the FD
is not active.
Both flags became equal in commit 82967bf9 ("MINOR: connection: adjust
CO_FL_NOTIFY_DATA after removal of flags"), which already predicted the
overlap between xprt_done_cb() and wake() after the removal of the DATA
specific flags in 1.8. Let's simply remove CO_FL_NOTIFY_DATA since the
"_DONE" version already covers everything and explains the intent well
enough.
The conn_fd_handler used to have one possible call to this function to
notify about end of handshakes, and another one to notify about connection
setup or error. But given that we're now only performing wakeup calls
after connection validation, we don't need to keep two places to run
this test since the conditions do not change in between.
This patch merges the two tests into a single one and moves the
CO_FL_CONNECTED test appropriately as well so that it's called even
on the error path if needed.
In conn_fd_handler() we used to first give a chance to the send()
callback to try to send data and validate the connection at the same
time. But since 1.9 we do not call this callback anymore inline, it's
scheduled. So let's validate the connection ealier so that all other
decisions can be taken based on this confirmation. This may notably
be useful to the xprt_done_cb() to know that the connection was
properly validated.
The function is not TCP-specific at all, it covers all FD-based sockets
so let's move this where other similar functions are, in connection.c,
and rename it conn_fd_check().
Now that we know what pollers can return ERR/HUP, we can take this
into account to save one syscall: with such a poller, if neither are
reported, then we know the connection succeeded and we don't need to
go with getsockopt() nor connect() to validate this. In addition, for
the remaining cases (select() or suspected errors), we'll always go
through the extra connect() attempt and enumerate possible "in progress",
"connected" or "failed" status codes and take action solely based on
this.
This results in one saved syscall on modern pollers, only a second
connect() still being used on select() and the server's address never
being needed anymore.
Note that we cannot safely replace connect() with getsockopt() as the
latter clears the error on the socket without saving it, and health
checks rely on it for their reporting. This would be OK if the error
was saved in the connection itself.
In practice it's all pollers except select(). It turns out that we're
keeping some legacy code only for select and enforcing it on all
pollers, let's offer the pollers the ability to declare that they
do not need that.
Since commit c3df4507fa ("MEDIUM: connections: Wake the upper layer even
if sending/receiving is disabled.") the send/recv callbacks are called
on I/O if the FD is ready and not just if it's active. This means that
in some situations (e.g. send ready but nothing to send) we may
needlessly enter the if() block, notice we're not subscribed, set
io_available=1 and call the wake() callback even if we're just called
for read activity. Better make sure we only do this when the FD is
active in that direction..
This may be backported as far as 2.0 though it should remain under
observation for a few weeks first as the risk of harm by a mistake
is higher than the trouble it should cause.
Two regtest regularly fail in a random fashion depending on the machine's
load (one could really wonder if it's really worth keeping such
unreproducible tests) :
- tcp-check_multiple_ports.vtc
- 4be_1srv_smtpchk_httpchk_layer47errors.vtc
It happens that one of the reason is the time it takes to connect to
the local socket (hence the load-dependent aspect): if connect() on the
loopback returns EINPROGRESS then this status is reported instead of a
real error. Normally such a test is expected to see the error cleaned
by tcp_connect_probe() but it really depends on the timing and instead
we may very well send() first and see this error. The problem is that
everything is collected based on errno, hoping it won't get molested
in the way from the last unsuccesful syscall to wake_srv_chk(), which
obviously is hard to guarantee.
This patch at least makes sure that a few non-errors are reported as
zero just like EAGAIN. It doesn't fix the root cause but makes it less
likely to report incorrect failures.
This fix could be backported as far as 1.9.
modifying LD_LIBRARY_PATH/DYLD_LIBRARY_PATH also affects other utilities like curl
to avoid side effects let us use rpath for ssl library linking
Fixes#418
SSL_CTX_set_ecdh_auto() is not defined when OpenSSL 1.1.1 is compiled
with the no-deprecated option. Remove existing, incomplete guards and
add a compatibility macro in openssl-compat.h, just as OpenSSL does:
bf4006a6f9/include/openssl/ssl.h (L1486)
This should be backported as far as 2.0 and probably even 1.9.
With a TCP frontend, it is possible to upgrade a connection to HTTP when the
backend is in HTTP mode. Concretly the upgrade install a new mux. So, once it is
done, the downgrade to TCP is no longer possible. So we must take care to never
assign a TCP backend to a stream on this connection. Otherwise, HAProxy crashes
because raw data from the server are handled as structured data on the client
side.
This patch fixes the issue #420. It must be backported to all versions
supporting the HTX.
A regression was introduced by the commit 76014fd1 ("MEDIUM: h1-htx: Add HTX EOM
block when the message is in H1_MSG_DONE state"). When nothing is copied in the
channel's buffer when the input message is parsed, we erroneously pretend it is
because there is not enough room by setting the CS_FL_WANT_ROOM flag on the
conn-stream. This happens when a partial request is parsed. Because of this
flag, we never try anymore to get input data from the mux because we first wait
for more room in the channel's buffer, which is empty. Because of this bug, it
is pretty easy to freeze a h1 connection.
To fix the bug, we must obsiously set the CS_FL_WANT_ROOM flag only when there
are still data to transfer while the channel's buffer is not empty.
This patch must be backported if the patch 76014fd1 is backported too. So for
now, no backport needed.
Issue #417 reports a possible memory leak in the state-file loading code.
There's one such place in the loop which corresponds to parsing errors
where the curreently allocated line is not freed when dropped. In any
case this is very minor in that no more than the file's length may be
lost in the worst case, considering that the whole file is kept anyway
in case of success. This fix addresses this.
It should be backported to 2.1.
The global state file tree isn't configured for unique keys, so if an
entry appears multiple times, e.g. due to a bogus script that concatenates
entries multiple times, this will needlessly eat memory. Let's just drop
duplicates.
This should be backported to 2.1.
Starting haproxy with a state file of 700k servers eats 11.2 GB of RAM
due to a mistake in the function that loads the strings into a tree: it
allocates a full buffer for each backend+server name instead of allocating
just the required string. By just fixing this we're down to 80 MB.
This should be backported to 2.1.
LIBRESSL_VERSION_NUMBER evaluates to 0 under OpenSSL, making the condition
always true. Check for the define before checking it.
Signed-off-by: Rosen Penev <rosenp@gmail.com>
[wt: to be backported as far as 1.9]
There's a very hard-to-trigger bug in the FD list code where the
fd_add_to_fd_list() function assumes that if the FD it's trying to add
is already locked, it's in the process of being added. Unfortunately, it
can also be in the process of being removed. It is very hard to trigger
because it requires that one thread is removing the FD while another one
is adding it. First very few FDs run on multiple threads (listeners and
DNS), and second, it does not make sense to add and remove the FD at the
same time.
In practice the DNS code built on the older callback-only model does
perform bursts of fd_want_send() for all resolvers at once when it wants
to send a new query (dns_send_query()). And this is more likely to happen
when here are lots of resolutions in parallel and many resolvers, because
the dns_response_recv() callback can also trigger a series of queries on
all resolvers for each invalid response it receives. This means that it
really is perfectly possible to both stop and start in parallel during
short periods of time there.
This issue was not reported before 2.1, but 2.1 had the FD cache, built
on the exact same code base. It's very possible that the issue caused
exactly the opposite situation, where an event was occasionally lost,
causing a DNS retry that worked, and nobody noticing the problem in the
end. In 2.1 the lost entries are the updates asking for not polling for
writes anymore, and the effect is that the poller contiuously reports
writability on the socket when the issue happens.
This patch fixes bug #416 and must be backported as far as 1.8, and
absolutely requires that previous commit "MINOR: fd/threads: make
_GET_NEXT()/_GET_PREV() use the volatile attribute" is backported as
well otherwise it will make the issue worse.
Special thanks to Julien Pivotto for setting up a reliable reproducer
for this difficult issue.
These macros are either used between atomic ops which cause the volatile
to be implicit, or with an explicit volatile cast. However not having it
in the macro causes some traps in the code because certain loop paths
cannot safely be used without risking infinite loops if one isn't careful
enough.
Let's place the volatile attribute inside the macros and remove them from
the explicit places to avoid this. It was verified that the output executable
remains exactly the same byte-wise.
Instead of attempting to read the early data only when the upper layer asks
for data, allocate a temporary buffer, stored in the ssl_sock_ctx, and put
all the early data in there. Requiring that the upper layer takes care of it
means that if for some reason the upper layer wants to emit data before it
has totally read the early data, we will be stuck forever.
This should be backported to 2.1 and 2.0.
This may fix github issue #411.
Since 1.9 with commit b20aa9eef3 ("MAJOR: tasks: create per-thread wait
queues") a task bound to a single thread will not use locks when being
queued or dequeued because the wait queue is assumed to be the owner
thread's.
But there exists a rare situation where this is not true: the health
check tasks may be running on one thread waiting for a response, and
may in parallel be requeued by another thread calling health_adjust()
after a detecting a response error in traffic when "observe l7" is set,
and "fastinter" is lower than "inter", requiring to shorten the running
check's timeout. In this case, the task being requeued was present in
another thread's wait queue, thus opening a race during task_unlink_wq(),
and gets requeued into the calling thread's wait queue instead of the
running one's, opening a second race here.
This patch aims at protecting against the risk of calling task_unlink_wq()
from one thread while the task is queued on another thread, hence unlocked,
by introducing a new TASK_SHARED_WQ flag.
This new flag indicates that a task's position in the wait queue may be
adjusted by other threads than then one currently executing it. This means
that such WQ manipulations must be performed under a lock. There are two
types of such tasks:
- the global ones, using the global wait queue (technically speaking,
those whose thread_mask has at least 2 bits set).
- some local ones, which for now will be placed into the global wait
queue as well in order to benefit from its lock.
The flag is automatically set on initialization if the task's thread mask
indicates more than one thread. The caller must also set it if it intends
to let other threads update the task's expiration delay (e.g. delegated
I/Os), or if it intends to change the task's affinity over time as this
could lead to the same situation.
Right now only the situation described above seems to be affected by this
issue, and it is very difficult to trigger, and even then, will often have
no visible effect beyond stopping the checks for example once the race is
met. On my laptop it is feasible with the following config, chained to
httpterm:
global
maxconn 400 # provoke FD errors, calling health_adjust()
defaults
mode http
timeout client 10s
timeout server 10s
timeout connect 10s
listen px
bind :8001
option httpchk /?t=50
server sback 127.0.0.1:8000 backup
server-template s 0-999 127.0.0.1:8000 check port 8001 inter 100 fastinter 10 observe layer7
This patch will automatically address the case for the checks because
check tasks are created with multiple threads bound and will get the
TASK_SHARED_WQ flag set.
If in the future more tasks need to rely on this (multi-threaded muxes
for example) and the use of the global wait queue becomes a bottleneck
again, then it should not be too difficult to place locks on the local
wait queues and queue the task on its bound thread.
This patch needs to be backported to 2.1, 2.0 and 1.9. It depends on
previous patch "MINOR: task: only check TASK_WOKEN_ANY to decide to
requeue a task".
Many thanks to William Dauchy for providing detailed traces allowing to
spot the problem.
After processing a task, its RUNNING bit is cleared and at the same time
we check for other bits to decide whether to requeue the task or not. It
happens that we only want to check the TASK_WOKEN_* bits, because :
- TASK_RUNNING was just cleared
- TASK_GLOBAL and TASK_QUEUE cannot be set yet as the task was running,
preventing it from being requeued
It's important not to catch yet undefined flags there because it would
prevent addition of new task flags. This also shows more clearly that
waking a task up with flags 0 is not something safe to do as the task
will not be woken up if it's already running.
Implement #REQUIRE_BINARIES for vtc files.
The run-regtests.sh script will check if the binary is available in the
environment, if not, it wil disable the vtc.
Add a reg-test which test the update of a certificate over the CLI. This
test requires socat and curl.
This commit also adds an ECDSA certificate in the ssl directory.
This action is very similar to "replace-uri" except that it only acts on the
path component. This is assumed to better match users' expectations when they
used to rely on "replace-uri" in HTTP/1 because mostly origin forms were used
in H1 while mostly absolute URI form is used in H2, and their rules very often
start with a '/', and as such do not match.
It could help users to get this backported to 2.0 and 2.1.
As discussed in the thread below [1], the debug converter is currently
not of much use given that it's only built when DEBUG_EXPR is set, and
it is limited to stderr only.
This patch changes this to make it take an optional prefix and an optional
target sink so that it can log to stdout, stderr or a ring buffer. The
default output is the "buf0" ring buffer, that can be consulted from the
CLI.
[1] https://www.mail-archive.com/haproxy@formilux.org/msg35671.html
Note: if this patch is backported, it also requires the following commit to
work: 46dfd78cbf ("BUG/MINOR: sample: always check converters' arguments").
Commit d4f946c ("MINOR: ssl/cli: 'show ssl cert' give information on the
certificates") introduced a build issue with openssl version < 1.0.2
because it uses the certificate bundles.
When accepting the max early data, don't set it on the SSL_CTX while parsing
the configuration, as at this point global.tune.maxrewrite may still be -1,
either because it was not set, or because it hasn't been set yet. Instead,
set it for each connection, just after we created the new SSL.
Not doing so meant that we could pretend to accept early data bigger than one
of our buffer.
This should be backported to 2.1, 2.0, 1.9 and 1.8.
Instead of failing the conversion when an invalid number of bits is
given the sha2 converter now fails with an appropriate error message
during startup.
The sha2 converter was introduced in d437630237,
which is in 2.1 and higher.
In 1.5-dev20, sample-fetch arguments parsing was addresse by commit
689a1df0a1 ("BUG/MEDIUM: sample: simplify and fix the argument parsing").
The issue was that argument checks were not run for sample-fetches if
parenthesis were not present. Surprisingly, the fix was mde only for
sample-fetches and not for converters which suffer from the exact same
problem. There are even a few comments in the code mentioning that some
argument validation functions are not called when arguments are missing.
This fix applies the exact same method as the one above. The impact of
this bug is limited because over the years the code has learned to work
around this issue instead of fixing it.
This may be backported to all maintained versions.
The closing bracket was emitted for the "debug" converter even when the
opening one was not sent, and the new line was not always emitted. Let's
fix this. This is harmless since this converter is not built by default.
With H2 deployments becoming more common, replace-uri starts to hit
users by not always matching absolute URIs due to rules expecting the
URI to start with a '/'.
This test checks that an HTTP message is properly processed when we failed to
add the HTX EOM block in an HTX message during the parsing because the buffer is
full. Some space must be released in the buffer to make it possible. This
requires an extra pass in the H1 multiplexer. Here, we must be sure the mux is
called while there is no more incoming data.
It is a "devel" test because conditions to run the test successfully is highly
dependent on the implementation. So if it fail, it is not necessarily a bug. It
may be due of an internal change. It relies on internal HTX sample fetches.
These sample fetches are internal and must be used for debugging purpose. Idea
is to have a way to add some checks on the HTX content from http rules. The main
purpose is to ease reg-tests writing.
During H1 parsing, the HTX EOM block is added before switching the message state
to H1_MSG_DONE. It is an exception in the way to convert an H1 message to
HTX. Except for this block, the message is first switched to the right state
before starting to add the corresponding HTX blocks. For instance, the message
is switched in H1_MSG_DATA state and then the HTX DATA blocks are added.
With this patch, the message is switched to the H1_MSG_DONE state when all data
blocks or trailers were processed. It is the caller responsibility to call
h1_parse_msg_eom() when the H1_MSG_DONE state is reached. This way, it is far
easier to catch failures when the HTX buffer is full.
The H1 and FCGI muxes have been updated accordingly.
This patch may eventually be backported to 2.1 if it helps other backports.
Apparently gcc developers decided that strncpy() semantics are no longer
valid and now deserve a warning, especially if used exactly as designed.
This results in issue #304. Let's just remove one to the target size to
please her majesty gcc, the God of C Compilers, who tries hard to make
users completely eliminate any use of string.h and reimplement it by
themselves at much higher risks. Pfff....
This can be backported to stable version, the fix is harmless since it
ignores the last zero that is already set on next line.
As reported in issue #380, the state check in listener_state_str() is
invalid as it allows state value 9 to report crap. We don't use such
a state value so the issue should never happen unless the memory is
already corrupted, but better clean this now while it's harmless.
This should be backported to all maintained branches.
As reported in issue #408, "agent-addr" doesn't work on default-server
lines. This is due to the transcription of the old "addr" option in commit
6e5e0d8f9e ("MINOR: server: Make 'default-server' support 'addr' keyword.")
which correctly assigns it to the check.addr and agent.addr fields, but
which also copies the default check.addr into both the check's and the
agent's addr fields. Thus the default agent's address is never used.
This fix makes sure to copy the check from the check and the agent from
the agent. However it's worth noting that if "addr" is specified on the
server line, it will still overwrite both the check and the agent's
addresses.
This must be backported as far as 1.8.
The listener supports a "transient error" situation, which corresponds
to those situations where accept fails badly but poll() reports an event.
This happens for example when a listener is paused, or on out of FD. The
same mechanism is used when facing a maxconn or maxsessrate limitation.
When this happens, the listener is disabled for up to 100ms and put back
into the global listener queue so that it automatically wakes up again
as soon as the conditions change from an existing connection releasing
one resource, or the system recovers from a transient issue.
The listener_accept() function has a bug in its exit path causing a
freshly limited listener to be immediately enabled again because all
the conditions are met (connection count < max). It doesn't take into
account the fact that the listener might have been queued and must
first wait for the timeout to expire before doing so. The impact is
that upon certain errors, the faulty process will busy loop on the
accept code without sleeping. This is the scenario reported and
diagnosed by @hedong0411 in issue #382.
This commit fixes it by verifying that the global queue's delay is
at least expired before deciding to resume the listener. Another
approach could consist in having an extra state like LI_DELAY for
situations where only a delay is acceptable, but this would probably
not bring anything except more complex code.
This issue was introduced with the lock-free listener accept code
(commits 3f0d02b and 82c9789a) that were backported to 1.8.20+ and
1.9.7+, so this fix must be backported to the relevant branches.
If a new process is started with -sf and it fails to bind, it may send
a SIGTTOU to the master process in hope that it will temporarily unbind.
Unfortunately this one doesn't catch it and stops to background instead
of forwarding the signal to the workers. The same is true for SIGTTIN.
This commit simply implements an extra signal handler for the master to
deal with such signals that must be passed down to the workers. It must
be backported as far as 1.8, though there the code differs in that it's
entirely in haproxy.c and doesn't require an extra sig handler.
As reported by Ilya in issue #392, Coverity found that we're leaking
allocated strings on error paths in parse_logformat(). Let's use a
proper exit label for failures instead of seeding return 0 everywhere.
This should be backported to all supported versions.
As mentionned in bug #405 we continue to reference architecture.txt from
places in the doc despite this file not being packaged for many years.
Better drop the reference if it's confusing.
We used to have wake_expired_tasks() wake up tasks and return the next
expiration delay. The problem this causes is that we have to call it just
before poll() in order to consider latest timers, but this also means that
we don't wake up all newly expired tasks upon return from poll(), which
thus systematically requires a second poll() round.
This is visible when running any scheduled task like a health check, as there
are systematically two poll() calls, one with the interval, nothing is done
after it, and another one with a zero delay, and the task is called:
listen test
bind *:8001
server s1 127.0.0.1:1111 check
09:37:38.200959 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=8696843}) = 0
09:37:38.200967 epoll_wait(3, [], 200, 1000) = 0
09:37:39.202459 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=8712467}) = 0
>> nothing run here, as the expired task was not woken up yet.
09:37:39.202497 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=8715766}) = 0
09:37:39.202505 epoll_wait(3, [], 200, 0) = 0
09:37:39.202513 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=8719064}) = 0
>> now the expired task was woken up
09:37:39.202522 socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) = 7
09:37:39.202537 fcntl(7, F_SETFL, O_RDONLY|O_NONBLOCK) = 0
09:37:39.202565 setsockopt(7, SOL_TCP, TCP_NODELAY, [1], 4) = 0
09:37:39.202577 setsockopt(7, SOL_TCP, TCP_QUICKACK, [0], 4) = 0
09:37:39.202585 connect(7, {sa_family=AF_INET, sin_port=htons(1111), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in progress)
09:37:39.202659 epoll_ctl(3, EPOLL_CTL_ADD, 7, {EPOLLOUT, {u32=7, u64=7}}) = 0
09:37:39.202673 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=8814713}) = 0
09:37:39.202683 epoll_wait(3, [{EPOLLOUT|EPOLLERR|EPOLLHUP, {u32=7, u64=7}}], 200, 1000) = 1
09:37:39.202693 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=8818617}) = 0
09:37:39.202701 getsockopt(7, SOL_SOCKET, SO_ERROR, [111], [4]) = 0
09:37:39.202715 close(7) = 0
Let's instead split the function in two parts:
- the first part, wake_expired_tasks(), called just before
process_runnable_tasks(), wakes up all expired tasks; it doesn't
compute any timeout.
- the second part, next_timer_expiry(), called just before poll(),
only computes the next timeout for the current thread.
Thanks to this, all expired tasks are properly woken up when leaving
poll, and each poll call's timeout remains up to date:
09:41:16.270449 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=10223556}) = 0
09:41:16.270457 epoll_wait(3, [], 200, 999) = 0
09:41:17.270130 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=10238572}) = 0
09:41:17.270157 socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) = 7
09:41:17.270194 fcntl(7, F_SETFL, O_RDONLY|O_NONBLOCK) = 0
09:41:17.270204 setsockopt(7, SOL_TCP, TCP_NODELAY, [1], 4) = 0
09:41:17.270216 setsockopt(7, SOL_TCP, TCP_QUICKACK, [0], 4) = 0
09:41:17.270224 connect(7, {sa_family=AF_INET, sin_port=htons(1111), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in progress)
09:41:17.270299 epoll_ctl(3, EPOLL_CTL_ADD, 7, {EPOLLOUT, {u32=7, u64=7}}) = 0
09:41:17.270314 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=10337841}) = 0
09:41:17.270323 epoll_wait(3, [{EPOLLOUT|EPOLLERR|EPOLLHUP, {u32=7, u64=7}}], 200, 1000) = 1
09:41:17.270332 clock_gettime(CLOCK_THREAD_CPUTIME_ID, {tv_sec=0, tv_nsec=10341860}) = 0
09:41:17.270340 getsockopt(7, SOL_SOCKET, SO_ERROR, [111], [4]) = 0
09:41:17.270367 close(7) = 0
This may be backported to 2.1 and 2.0 though it's unlikely to bring any
user-visible improvement except to clarify debugging.
