In continuity of previous patch, this one makes use of the new profiling
flags. For this, based on the global "profiling" setting, when switching
profiling on, we set or clear two flags on the thread context,
TH_FL_TASK_PROFILING_L and TH_FL_TASK_PROFILING_M to indicate whether
lock profiling and/or malloc profiling are desired when profiling is
enabled. These flags are checked along with TH_FL_TASK_PROFILING to
decide when to collect time around a lock or a malloc. And by default
we're back to the behavior of 3.2 in that neither lock nor malloc times
are collected anymore.
This is sufficient to see the CPU usage spent in the VDSO to significantly
drop from 22% to 2.2% on a highly loaded system.
This should be backported to 3.3 along with the previous patch.
Now that it is unused, eliminate all_tgroups_mask, as we can't 64bits
masks to represent thread groups, if we want to be able to have more
than 64 thread groups.
When DEBUG_THREAD > 0 and task profiling enabled, we'll now measure the
time spent with at least one lock held for each task. The time is
collected by locking operations when locks are taken raising the level
to one, or released resetting the level. An accumulator is updated in
the thread_ctx struct that is collected by the scheduler when the task
returns, and updated in the sched_activity entry of the related task.
This allows to observe figures like this one:
Tasks activity over 259.516 sec till 0.000 sec ago:
function calls cpu_tot cpu_avg lkw_avg lkd_avg lat_avg
h1_io_cb 15466589 2.574m 9.984us - - 33.45us <- sock_conn_iocb@src/sock.c:1099 tasklet_wakeup
sc_conn_io_cb 8047994 8.325s 1.034us - - 870.1us <- sc_app_chk_rcv_conn@src/stconn.c:844 tasklet_wakeup
process_stream 7734689 4.356m 33.79us 1.990us 1.641us 1.554ms <- sc_notify@src/stconn.c:1206 task_wakeup
process_stream 7734292 46.74m 362.6us 278.3us 132.2us 972.0us <- stream_new@src/stream.c:585 task_wakeup
sc_conn_io_cb 7733158 46.88s 6.061us - - 68.78us <- h1_wake_stream_for_recv@src/mux_h1.c:3633 tasklet_wakeup
task_process_applet 6603593 4.484m 40.74us 16.69us 34.00us 96.47us <- sc_app_chk_snd_applet@src/stconn.c:1043 appctx_wakeup
task_process_applet 4761796 3.420m 43.09us 18.79us 39.28us 138.2us <- __process_running_peer_sync@src/peers.c:3579 appctx_wakeup
process_table_expire 4710662 4.880m 62.16us 9.648us 53.95us 158.6us <- run_tasks_from_lists@src/task.c:671 task_queue
stktable_add_pend_updates 4171868 6.786s 1.626us - 1.487us 47.94us <- stktable_add_pend_updates@src/stick_table.c:869 tasklet_wakeup
h1_io_cb 2871683 1.198s 417.0ns 70.00ns 69.00ns 1.005ms <- h1_takeover@src/mux_h1.c:5659 tasklet_wakeup
process_peer_sync 2304957 5.368s 2.328us - 1.156us 68.54us <- stktable_add_pend_updates@src/stick_table.c:873 task_wakeup
process_peer_sync 1388141 3.174s 2.286us - 1.130us 52.31us <- run_tasks_from_lists@src/task.c:671 task_queue
stktable_add_pend_updates 463488 3.530s 7.615us 2.000ns 7.134us 771.2us <- stktable_touch_with_exp@src/stick_table.c:654 tasklet_wakeup
Here we see that almost the entirety of stktable_add_pend_updates() is
spent under a lock, that 1/3 of the execution time of process_stream()
was performed under a lock and that 2/3 of it was spent waiting for a
lock (this is related to the 10 track-sc present in this config), and
that the locking time in process_peer_sync() has now significantly
reduced. This is more visible with "show profiling tasks aggr":
Tasks activity over 475.354 sec till 0.000 sec ago:
function calls cpu_tot cpu_avg lkw_avg lkd_avg lat_avg
h1_io_cb 25742539 3.699m 8.622us 11.00ns 10.00ns 188.0us
sc_conn_io_cb 22565666 1.475m 3.920us - - 473.9us
process_stream 21665212 1.195h 198.6us 140.6us 67.08us 1.266ms
task_process_applet 16352495 11.31m 41.51us 17.98us 36.55us 112.3us
process_peer_sync 7831923 17.15s 2.189us - 1.107us 41.27us
process_table_expire 6878569 6.866m 59.89us 9.359us 51.91us 151.8us
stktable_add_pend_updates 6602502 14.77s 2.236us - 2.060us 119.8us
h1_timeout_task 801 703.4us 878.0ns - - 185.7us
srv_cleanup_toremove_conns 347 12.43ms 35.82us 240.0ns 70.00ns 1.924ms
accept_queue_process 142 1.384ms 9.743us - - 340.6us
srv_cleanup_idle_conns 74 475.0us 6.418us 896.0ns 5.667us 114.6us
The new lock_level field indicates the number of cumulated locks that
are held by the current thread. It's fed as soon as DEBUG_THREAD is at
least 1. In addition, thread_isolate() adds 128, so that it's even
possible to check for combinations of both. The value is also reported
in thread dumps (warnings and panics).
When DEBUG_THREAD > 0, and if task profiling is enabled, then each
locking attempt will measure the time it takes to obtain the lock, then
add that time to a thread_ctx accumulator that the scheduler will then
retrieve to update the current task's sched_activity entry. The value
will then appear avearaged over the number of calls in the lkw_avg column
of "show profiling tasks", such as below:
Tasks activity over 48.298 sec till 0.000 sec ago:
function calls cpu_tot cpu_avg lkw_avg lat_avg
h1_io_cb 3200170 26.81s 8.377us - 32.73us <- sock_conn_iocb@src/sock.c:1099 tasklet_wakeup
sc_conn_io_cb 1657841 1.645s 992.0ns - 853.0us <- sc_app_chk_rcv_conn@src/stconn.c:844 tasklet_wakeup
process_stream 1600450 49.16s 30.71us 1.936us 1.392ms <- sc_notify@src/stconn.c:1206 task_wakeup
process_stream 1600321 7.770m 291.3us 209.1us 901.6us <- stream_new@src/stream.c:585 task_wakeup
sc_conn_io_cb 1599928 7.975s 4.984us - 65.77us <- h1_wake_stream_for_recv@src/mux_h1.c:3633 tasklet_wakeup
task_process_applet 997609 46.37s 46.48us 16.80us 113.0us <- sc_app_chk_snd_applet@src/stconn.c:1043 appctx_wakeup
process_table_expire 922074 48.79s 52.92us 7.275us 181.1us <- run_tasks_from_lists@src/task.c:670 task_queue
stktable_add_pend_updates 705423 1.511s 2.142us - 56.81us <- stktable_add_pend_updates@src/stick_table.c:869 tasklet_wakeup
task_process_applet 683511 34.75s 50.84us 18.37us 153.3us <- __process_running_peer_sync@src/peers.c:3579 appctx_wakeup
h1_io_cb 535395 198.1ms 370.0ns 72.00ns 930.4us <- h1_takeover@src/mux_h1.c:5659 tasklet_wakeup
It now makes it pretty obvious which tasks (hence call chains) spend their
time waiting on a lock and for what share of their execution time.
In order to make the lock history a bit more useful, let's try to merge
adjacent lock/unlock sequences that don't change anything for other
threads. For this we can replace the last unlock with the new operation
on the same label, and even just not store it if it was the same as the
one before the unlock, since in the end it's the same as if the unlock
had not been done.
Now loops that used to be filled with "R:LISTENER U:LISTENER" show more
useful info such as:
S:IDLE_CONNS U:IDLE_CONNS S:PEER U:PEER S:IDLE_CONNS U:IDLE_CONNS R:LISTENER U:LISTENER
U:STK_TABLE W:STK_SESS U:STK_SESS R:STK_TABLE U:STK_TABLE W:STK_SESS U:STK_SESS R:STK_TABLE
R:STK_TABLE U:STK_TABLE W:STK_SESS U:STK_SESS W:STK_TABLE_UPDT U:STK_TABLE_UPDT S:PEER
It's worth noting that it can sometimes induce confusion when recursive
locks of the same label are used (a few exist on peers or stick-tables),
as in such a case the two operations would be needed. However these ones
are already undebuggable, so instead they will just have to be renamed
to make sure they use a distinct label.
Most threads are filled with "R:OTHER U:OTHER" in their history. Since
anything non-important can use other it's not observable but it pollutes
the history. Let's just drop OTHER entirely during the recording.
Define a new type "struct cshared". This can be used as a tool to
manipulate a global counter with thread-safety ensured. Each thread
would declare its thread-local cshared type, which would point to a
global counter.
Each thread can then add/substract value to their owned thread-local
cshared instance via cshared_add(). If the difference exceed a
configured limit, either positively or negatively, the global counter is
updated and thread-local instance is reset to 0. Each thread can safely
read the global counter value using cshared_read().
This will display the lock labels and modes for each non-empty step
at the end of "show threads" when these are defined. This allows to
emit up to the last 8 locking operation for each thread on 64 bit
machines.
by only storing a word in each thread context, we can keep the history
of all taken/dropped locks by label. This is expected to be very cheap
and to permit to store up to 8 consecutive lock operations in 64 bits.
That should significantly help detect recursive locks as well as figure
what thread was likely to hinder another one waiting for a lock.
For now we only store the final state of the lock, we don't store the
attempt to get it. It's just a matter of space since we already need
4 ops (rd,sk,wr,un) which take 2 bits, leaving max 64 labels. We're
already around 45. We could also multiply by 5 and still keep 8 bits
total per lock, that would limit us to 51 locks max. It seems that
most of the time if we get a watchdog panic, anyway the victim thread
will be perfectly located so that we don't need a specific value for
this. Another benefit is that we perform a single memory write per
lock.
We now default the value to zero and make sure all tests properly take
care of values above zero. This is in preparation for supporting several
degrees of debugging.
Some signal handlers rely on these to decide about the level of detail to
provide in dumps, so let's properly fill the info about entering/leaving
idle. Note that for consistency with other tests we're using bitops with
t->ltid_bit, while we could simply assign 0/1 to the fields. But it makes
the code more readable and the whole difference is only 88 bytes on a 3MB
executable.
This bug is not important, and while older versions are likely affected
as well, it's not worth taking the risk to backport this in case it would
wake up an obscure bug.
By mutually refining the thread count and group count, we can try
to detect the most suitable setup for the current machine. Taskset
is implicitly handled correctly. tgroups automatically adapt to the
configured number of threads. cpu-map manages to limit tgroups to
the smallest supported value.
The thread-limit is enforced. Just like in cfgparse, if the thread
count was forced to a higher value, it's reduced and a warning is
emitted. But if it was not set, the thr_max value is bound to this
limit so that further calculations respect it.
We continue to default to the max number of available threads and 1
tgroup by default, with the limit. This normally allows to get rid
of that test in check_config_validity().
The function is not convenient because it doesn't allow us to undo the
startup changes, and depending on where it's being used, we don't know
whether the values read have already been altered (this is not the case
right now but it's going to evolve).
Let's just compute the status during cpu_detect_usable() and set a
variable accordingly. This way we'll always read the init value, and
if needed we can even afford to reset it. Also, placing it in cpu_topo.c
limits cross-file dependencies (e.g. threads without affinity etc).
Every use of the cache tree was covered by the shctx lock even when no
operations were performed on the shared_context lists (avail and hot).
This patch adds a dedicated RW lock for the cache so that blocks of code
that work on the cache tree only can use this lock instead of the
superseding shctx one. This is useful for operations during which the
concerned blocks are already in the hot list.
When the two locks need to be taken at the same time, in
http_action_req_cache_use and in shctx_row_reserve_hot, the shctx one
must be taken first.
A new parameter needed to be added to the shared_context's free_block
callback prototype so that cache_free_block can take the cache lock and
release it afterwards.
The ring lock was initially mostly used for the logs and used to inherit
its name in lock stats. Now that it's exclusively used by rings, let's
rename it accordingly.
This detects when there are more threads bound via cpu-map than CPUs
enabled in cpu-map, or when there are more total threads than the total
number of CPUs available at boot (for unbound threads) and configured
for bound threads. In this case, a warning is emitted to explain the
problems it will cause, and explaining how to address the situation.
Note that some configurations will not be detected as faulty because
the algorithmic complexity to resolve all arrangements grows in O(N!).
This means that having 3 threads on 2 CPUs and one thread on 2 CPUs
will not be detected as it's 4 threads for 4 CPUs. But at least configs
such as T0:(1,4) T1:(1,4) T2:(2,4) T3:(3,4) will not trigger a warning
since they're valid.
It's very easy to mess up with some cpu-map directives and to leave
some thread unbound. Let's add a test that checks that either all
threads are bound or none are bound, but that we do not face the
intermediary situation where some are pinned and others are left
wandering around, possibly on the same CPUs as bound ones.
Note that this should not be backported, or maybe turned into a
notice only, as it appears that it will easily catch invalid
configs and that may break updates for some users.
When using pthread_rwlock emulation, contention is reported on
pl_wait_unlock_long(). This is really not convenient to analyse what is
happening. Now plock supports inlining the wait call for just the lorw
functions by enabling PLOCK_LORW_INLINE_WAIT. Let's do this so that now
the wait time will be precisely reported as either pthread_rwlock_rdlock()
or pthread_rwlock_wrlock() depending on the contended function, but no
more on pl_wait_unlock_long(), which will still be reported for all
other locks.
Previously, quic_connection_id were stored in a per-thread tree list.
Datagram were first dispatched to the correct thread using the encoded
TID before a tree lookup was done.
Remove these trees and replace it with a global trees list of 256
entries. A CID is using the list index corresponding to its first byte.
On datagram dispatch, CID is lookup on its tree and TID is retrieved
using new member quic_connection_id.tid. As such, a read-write lock
protects each list instances. With 256 entries, it is expected that
contention should be reduced.
A new structure quic_cid_tree served as a tree container associated with
its read-write lock. An API is implemented to ensure lock safety for
insert/lookup/delete operation.
This patch is a step forward to be able to break the affinity between a
CID and a TID encoded thread. This is required to be able to migrate a
quic_conn after accept to select thread based on their load.
This should be backported up to 2.7 after a period of observation.
QUIC_LOCK label is never used. Indeed, lock usage is minimal on QUIC as
every connection is pinned to its owned thread.
This should be backported up to 2.7.
soft-stop was not explicitly handled in event_hdl API.
Because of this, event_hdl was causing some leaks on deinit paths.
Moreover, a task responsible for handling events could require some
additional cleanups (ie: advanced async task), and as the task was not
protected against abort when soft-stopping, such cleanup could not be
performed unless the task itself implements the required protections,
which is not optimal.
Consider this new approach:
'jobs' global variable is incremented whenever an async subscription is
created to prevent the related task from being aborted before the task
acknowledges the final END event.
Once the END event is acknowledged and freed by the task, the 'jobs'
variable is decremented, and the deinit process may continue (including
the abortion of remaining tasks not guarded by the 'jobs' variable).
To do this, a new global mt_list is required: known_event_hdl_sub_list
This list tracks the known (initialized) subscription lists within the
process.
sub_lists are automatically added to the "known" list when calling
event_hdl_sub_list_init(), and are removed from the list with
event_hdl_sub_list_destroy().
This allows us to implement a global thread-safe event_hdl deinit()
function that is automatically called on soft-stop thanks to signal(0).
When event_hdl deinit() is initiated, we simply iterate against the known
subscription lists to destroy them.
event_hdl_subscribe_ptr() was slightly modified to make sure that a sub_list
may not accept new subscriptions once it is destroyed (removed from the
known list)
This can occur between the time the soft-stop is initiated (signal(0)) and
haproxy actually enters in the deinit() function (once tasks are either
finished or aborted and other threads already joined).
It is safe to destroy() the subscription list multiple times as long
as the pointer is still valid (ie: first on soft-stop when handling
the '0' signal, then from regular deinit() path): the function does
nothing if the subscription list is already removed.
We partially reverted "BUG/MINOR: event_hdl: make event_hdl_subscribe thread-safe"
since we can use parent mt_list locking instead of a dedicated lock to make
the check gainst duplicate subscription ID.
(insert_lock is not useful anymore)
The check in itself is not changed, only the locking method.
sizeof(event_hdl_sub_list) slightly increases: from 24 bits to 32bits due
to the additional mt_list struct within it.
With that said, having thread-safe list to store known subscription lists
is a good thing: it could help to implement additional management
logic for subcription lists and could be useful to add some stats or
debugging tools in the future.
If 68e692da0 ("MINOR: event_hdl: add event handler base api")
is being backported, then this commit should be backported with it.
List insertion in event_hdl_subscribe() was not thread-safe when dealing
with unique identifiers. Indeed, in this case the list insertion is
conditional (we check for a duplicate, then we insert). And while we're
using mt lists for this, the whole operation is not atomic: there is a
race between the check and the insertion.
This could lead to the same ID being registered multiple times with
concurrent calls to event_hdl_subscribe() on the same ID.
To fix this, we add 'insert_lock' dedicated lock in the subscription
list struct. The lock's cost is nearly 0 since it is only used when
registering identified subscriptions and the lock window is very short:
we only guard the duplicate check and the list insertion to make the
conditional insertion "atomic" within a given subscription list.
This is the only place where we need the lock: as soon as the item is
properly inserted we're out of trouble because all other operations on
the list are already thread-safe thanks to mt lists.
A new lock hint is introduced: LOCK_EHDL which is dedicated to event_hdl
The patch may seem quite large since we had to rework the logic around
the subscribe function and switch from simple mt_list to a dedicated
struct wrapping both the mt_list and the insert_lock for the
event_hdl_sub_list type.
(sizeof(event_hdl_sub_list) is now 24 instead of 16)
However, all the changes are internal: we don't break the API.
If 68e692da0 ("MINOR: event_hdl: add event handler base api")
is being backported, then this commit should be backported with it.
Building without thread support was broken in 2.8-dev2 with commit
7e70bfc8c ("MINOR: threads: add a thread_harmless_end() version that
doesn't wait") that forgot to define the function for the threadless
cases. No backport is needed.
Instead of reading and storing a single group and a single mask for a
"thread" directive on a bind line, we now store the complete range in
a thread set that's stored in the bind_conf. The bind_parse_thread()
function now just calls parse_thread_set() to complete the current set,
which starts empty, and thread_resolve_group_mask() was updated to
support retrieving thread group numbers or absolute thread numbers
directly from the pre-filled thread_set, and continue to feed bind_tgroup
and bind_thread. The CLI parsers which were pre-initialized to set the
bind_tgroup to 1 cannot do it anymore as it would prevent one from
restricting the thread set. Instead check_config_validity() now detects
the CLI frontend and passes the info down to thread_resolve_group_mask()
that will automatically use only the group 1's threads for these
listeners. The same is done for the peers listeners for now.
At this step it's already possible to start with all previous valid
configs as well as extended ones supporting comma-delimited thread
sets. In addition the parser already accepts large ranges spanning
multiple groups, but since the underlying listeners infrastructure
is not read, for now we're maintaining a specific check against this
at the higher level of the config validity check.
The patch is a bit large because thread resolution is performed in
multiple steps, so we need to adjust all of them at once to preserve
functional and technical consistency.
The purpose is to be able to store large thread sets, defined by ranges
that may cross group boundaries, as well as define lists of groups and
masks. The thread_set struct implements the storage, and the parser is
in parse_thread_set(), with a focus on "bind" lines, but not only.
thread_harmless_end() needs to wait for rdv_requests to disappear so
that we're certain to respect a harmless promise that possibly allowed
another thread to proceed under isolation. But this doesn't work in a
signal handler because a thread could be interrupted by the debug
handler while already waiting for isolation and with rdv_request>0.
As such this function could cause a deadlock in such a signal handler.
Let's implement a specific variant for this, thread_harmless_end_sig(),
that just resets the thread's bit and doesn't wait. It must of course
not be used past a check point that would allow the isolation requester
to return and see the thread as temporarily harmless then turning back
on its promise.
This will be needed to fix a race in the debug handler.
The tree that contains OCSP responses is never locked despite being used
at runtime for OCSP stapling as well as the CLI through "set ssl cert"
and "set ssl ocsp-response" commands.
Everything works though because the certificate_ocsp structure is
refcounted and the tree's entries are cleaned up when SSL_CTXs are
destroyed (thanks to an ex_data entry in which the certificate_ocsp
pointer is stored).
This new lock will come to use when the OCSP auto update mechanism is
fully implemented because this new feature will be based on another tree
that stores the same certificate_ocsp members and updates their contents
periodically.
Since these are not used anymore, let's now remove them. Given the
number of places where we're using ti->ldit_bit, maybe an equivalent
might be useful though.
Since commit d2494e048 ("BUG/MEDIUM: peers/config: properly set the
thread mask") there must not remain any single case of a receiver that
is bound nowhere, so there's no need anymore for thread_mask().
We're adding a test in fd_insert() to make sure this doesn't happen by
accident though, but the function was removed and its rare uses were
replaced with the original value of the bind_thread msak.
The harmless status is not re-entrant, so sometimes for signal handling
it can be useful to know if we're already harmless or not. Let's add a
function doing that, and make the debugger use it instead of manipulating
the harmless mask.
thread_isolate() and thread_isolate_full() were relying on a set of thread
masks for all threads in different states (rdv, harmless, idle). This cannot
work anymore when the number of threads increases beyond LONGBITS so we need
to change the mechanism.
What is done here is to have a counter of requesters and the number of the
current isolated thread. Threads which want to isolate themselves increment
the request counter and wait for all threads to be marked harmless (or idle)
by scanning all groups and watching the respective masks. This is possible
because threads cannot escape once they discover this counter, unless they
also want to isolate and possibly pass first. Once all threads are harmless,
the requesting thread tries to self-assign the isolated thread number, and
if it fails it loops back to checking all threads. If it wins it's guaranted
to be alone, and can drop its harmless bit, so that other competing threads
go back to the loop waiting for all threads to be harmless. The benefit of
proceeding this way is that there's very little write contention on the
thread number (none during work), hence no cache line moves between caches,
thus frozen threads do not slow down the isolated one.
Once it's done, the isolated thread resets the thread number (hence lets
another thread take the place) and decrements the requester count, thus
possibly releasing all harmless threads.
With this change there's no more need for any global mask to synchronize
any thread, and we only need to loop over a number of groups to check
64 threads at a time per iteration. As such, tinfo's threads_want_rdv
could be dropped.
This was tested with 64 threads spread into 2 groups, running 64 tasks
(from the debug dev command), 20 "show sess" (thread_isolate()), 20
"add server blah/blah" (thread_isolate()), and 20 "del server blah/blah"
(thread_isolate_full()). The load remained very low (limited by external
socat forks) and no stuck nor starved thread was found.
The thread group info is not sufficient to represent a thread group's
current state as it's read-only. We also need something comparable to
the thread context to represent the aggregate state of the threads in
that group. This patch introduces ha_tgroup_ctx[] and tg_ctx for this.
It's indexed on the group id and must be cache-line aligned. The thread
masks that were global and that do not need to remain global were moved
there (want_rdv, harmless, idle).
Given that all the masks placed there now become group-specific, the
associated thread mask (tid_bit) now switches to the thread's local
bit (ltid_bit). Both are the same for nbtgroups 1 but will differ for
other values.
There's also a tg_ctx pointer in the thread so that it can be reached
from other threads.
This function was added in 2.0 when reworking the thread isolation
mechanism to make it more reliable. However it if fundamentally
incompatible with the full isolation mechanism provided by
thread_isolate_full() since that one will wait for all threads to
become idle while the former will wait for all threads to finish
waiting, causing a deadlock.
Given that it's not used, let's just drop it entirely before it gets
used by accident.
In order to kill all_threads_mask we'll need to have an equivalent for
the thread groups. The all_tgroups_mask does just this, it keeps one bit
set per enabled group.
At several places we're dereferencing the thread group just to catch
the group number, and this will become even more required once we start
to use per-group contexts. Let's just add the tgid in the thread_info
struct to make this easier.
For now we still set tid_bit to (1UL << tid) because FDs will not
work with more than one group without this, but once FDs start to
adopt local masks this must change to thr->ltid_bit.
Each thread has its own local thread id and its own global thread id,
in addition to the masks corresponding to each. Once the global thread
ID can go beyond 64 it will not be possible to have a global thread Id
bit anymore, so better start to remove it and use only the local one
from the struct thread_info.
In the configuration sometimes we'll omit a thread group number to designate
a global thread number range, and sometimes we'll mention the group and
designate IDs within that group. The operation is more complex than it
seems due to the need to check for ranges spanning between multiple groups
and determining groups from threads from bit masks and remapping bit masks
between local/global.
This patch adds a function to perform this operation, it takes a group and
mask on input and updates them on output. It's designed to be used by "bind"
lines but will likely be usable at other places if needed.
For situations where specified threads do not exist in the group, we have
the choice in the code between silently fixing the thread set or failing
with a message. For now the better option seems to return an error, but if
it turns out to be an issue we can easily change that in the future. Note
that it should only happen with "x/even" when group x only has one thread.
This is the equivalent of "tid" for ease of access. In the future if we
make th_cfg a pure thread-local array (not a pointer), it may make sense
to move it there.
ha_set_tid() was randomly used either to explicitly set thread 0 or to
set any possibly incomplete thread during boot. Let's replace it with
a pointer to a valid thread or NULL for any thread. This allows us to
check that the designated threads are always valid, and to ignore the
thread 0's mapping when setting it to NULL, and always use group 0 with
it during boot.
The initialization code is also cleaner, as we don't pass ugly casts
of a thread ID to a pointer anymore.
This takes care of unassigned threads groups and places unassigned
threads there, in a more or less balanced way. Too sparse allocations
may still fail though. For now with a maximum group number fixed to 1
nothing can really fail.
A the "tg" thread-local variable now always points to the current
thread group. It's pre-initializd to the first one during boot and is
set to point to the thread's one by ha_set_tid(). This last one takes
care of checking whether the thread group was assigned or not because
it may be called during boot before threads are initialized.
The scheduler contains a lot of stuff that is thread-local and not
exclusively tied to the scheduler. Other parts (namely thread_info)
contain similar thread-local context that ought to be merged with
it but that is even less related to the scheduler. However moving
more data into this structure isn't possible since task.h is high
level and cannot be included everywhere (e.g. activity) without
causing include loops.
In the end, it appears that the task_per_thread represents most of
the per-thread context defined with generic types and should simply
move to tinfo.h so that everyone can use them.
The struct was renamed to thread_ctx and the variable "sched" was
renamed to "th_ctx". "sched" used to be initialized manually from
run_thread_poll_loop(), now it's initialized by ha_set_tid() just
like ti, tid, tid_bit.
The memset() in init_task() was removed in favor of a bss initialization
of the array, so that other subsystems can put their stuff in this array.
Since the tasklet array has TL_CLASSES elements, the TL_* definitions
was moved there as well, but it's not a problem.
The vast majority of the change in this patch is caused by the
renaming of the structures.
These ones are rarely used or only to waste CPU cycles waiting, and are
the last ones requiring system includes in thread.h. Let's uninline them
and move them to thread.c.
