The shctx lock was changed from a SPINLOCK to a RWLOCK in commit ed35b94
"MEDIUM: cache: Switch shctx spinlock to rwlock and restrict its scope"
but a SPIN_INIT was left behind.
This patch does not need to be backported.
This global variable was used to avoid using locks on shared_contexts in
the unlikely case of nbthread==1. Since the locks do not do anything
when USE_THREAD is not defined, it will be more beneficial to simply
remove this variable and the systematic test on its value in the shared
context locking functions.
This patch adds a reserve_finish callback that can be defined by the
subsystems that require a shared_context. It is called at the end of
shctx_row_reserve_hot after the shared_context lock is released.
Descend the shctx_lock calls into the shctx_row_reserve_hot so that the
cases when we don't need to lock anything (enough space in the current
row or not enough space in the 'avail' list) do not take the lock at
all.
In sh_ssl_sess_new_cb the lock had to be descended into
sh_ssl_sess_store in order not to cover the shctx_row_reserve_hot call
anymore.
Since a lock on the cache tree was added in the latest cache changes, we
do not need to use the shared_context's lock to lock more than pure
shared_context related data anymore. This already existing lock will now
only cover the 'avail' list from the shared_context. It can then be
changed to a rwlock instead of a spinlock because we might want to only
run through the avail list sometimes.
Apart form changing the type of the shctx lock, the main modification
introduced by this patch is to limit the amount of code covered by the
shctx lock. This lock does not need to cover any code strictly related
to the cache tree anymore.
The "hot" list stored in a shared_context was used to keep a reference
to shared blocks that were currently being used and were thus removed
from the available list (so that they don't get reused for another cache
response). This 'hot' list does not ever need to be shared across
threads since every one of them only works on their current row.
The main need behind this 'hot' list was to detach the corresponding
blocks from the 'avail' list and to have a known list root when calling
list_for_each_entry_from in shctx_row_data_append (for instance).
Since we actually never need to iterate over all members of the 'hot'
list, we can remove it and replace the inc_hot/dec_hot logic by a
detach/reattach one.
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 shctx_row_reserve_hot relied on two loop levels in order to first
look for the first block of a preused row and then iterate on all the
blocks of this row to reserve them for the new row. This was not the
simplest nor the easiest to read way so this logic could be replaced by
a single iteration on the avail list members.
The two use cases of calling this function with or without a preexisting
"first" member were a bit cumbersome as well and were replaced by a more
straightforward approach.
Instead of iterating over all the elements of a given row when moving it
between the hot and available lists, we can make use of the last_reserved
pointer that already points to the last block of the list to perform the
move in O(1).
Ensure that the last_append pointer is always set to NULL on first block
of rows reserved by the subsystems using the shctx (cache for instance).
This pointer will be used directly in shctx_row_data_append instead of
the 'from' param which will simplify its uses.
The shctx code relies on sensitive conditions that are hard to infer
from the code itself, let's add some BUG_ON() to verify them. They
helped spot the previous bugs.
In shctx_row_reserve_hot() we only leave if we've found the exact
requested size instead of at least as large, as is documented. This
results in extra lookups and free calls in the avail loop while it is
not needed, and participates to seeing a negative data_len early as
spotted in previous bugs.
It doesn't seem to have any other impact however, but it's better to
backport it to stable branches.
In shctx_row_reserve_hot(), a missing break allows the avail loop to
loop for a while after having allocated the required blocks, possibly
leading to the point where it could trigger the watchdog after checking
up to 2 million blocks. In addition, the extra iteration may leave one
block assigned with size zero at the head of the avail list, and mark
it as being an isolated chain of 1 block. It's unclear whether this
could have had other consequences.
There is a non-negligible chance that it addreses bugs #1451 and #1284,
as the pattern observed in the loop looks exactly the same as the one
reported there in the crashes.
It's only marked medium because it is extremely hard to trigger. Here
the conditions were reproduced when starting 4k connections at once
requesting objects of random sizes between 0 and 20k to store them into
a small 1MB cache. However the watchdog will never trigger in such a case
so one needs to instrument the functions.
Thanks to Sohaib Ahmad and @g0uZ for providing useful traces.
This will need to be backported to all stable branches.
With a single process, we don't need to USE_PRIVATE_CACHE, USE_FUTEX
nor USE_PTHREAD_PSHARED anymore. Let's only keep the basic spinlock
to lock between threads.
Since threads were introduced in 1.8, the USE_PRIVATE_CACHE mode of the
shctx was not updated to use locks. Originally it was meant to disable
sharing between processes, so it removes the lock/unlock instructions.
But with threads enabled, it's not possible to work like this anymore.
It's easy to see that once built with private cache and threads enabled,
sending violent SSL traffic to the the process instantly makes it die.
The HTTP cache is very likely affected as well.
This patch addresses this by falling back to our native spinlocks when
USE_PRIVATE_CACHE is used. In practice we could use them also for other
modes and remove all older implementations, but this patch aims at keeping
the changes very low and easy to backport. A new SHCTX_LOCK label was
added to help with debugging, but OTHER_LOCK might be usable as well
for backports.
An even lighter approach for backports may consist in always declaring
the lock (or reusing "waiters"), and calling pl_take_s() for the lock()
and pl_drop_s() for the unlock() operation. This could even be used in
all modes (process and threads), even when thread support is disabled.
Subsequent patches will further clean up this area.
This patch must be backported to all supported versions since 1.8.
The current "ADD" vs "ADDQ" is confusing because when thinking in terms
of appending at the end of a list, "ADD" naturally comes to mind, but
here it does the opposite, it inserts. Several times already it's been
incorrectly used where ADDQ was expected, the latest of which was a
fortunate accident explained in 6fa922562 ("CLEANUP: stream: explain
why we queue the stream at the head of the server list").
Let's use more explicit (but slightly longer) names now:
LIST_ADD -> LIST_INSERT
LIST_ADDQ -> LIST_APPEND
LIST_ADDED -> LIST_INLIST
LIST_DEL -> LIST_DELETE
The same is true for MT_LISTs, including their "TRY" variant.
LIST_DEL_INIT keeps its short name to encourage to use it instead of the
lazier LIST_DELETE which is often less safe.
The change is large (~674 non-comment entries) but is mechanical enough
to remain safe. No permutation was performed, so any out-of-tree code
can easily map older names to new ones.
The list doc was updated.
global.h was one of the messiest files, it has accumulated tons of
implicit dependencies and declares many globals that make almost all
other file include it. It managed to silence a dependency loop between
server.h and proxy.h by being well placed to pre-define the required
structs, forcing struct proxy and struct server to be forward-declared
in a significant number of files.
It was split in to, one which is the global struct definition and the
few macros and flags, and the rest containing the functions prototypes.
The UNIX_MAX_PATH definition was moved to compat.h.
Half of the users of this include only need the type definitions and
not the manipulation macros nor the inline functions. Moves the various
types into mini-clist-t.h makes the files cleaner. The other one had all
its includes grouped at the top. A few files continued to reference it
without using it and were cleaned.
In addition it was about time that we'd rename that file, it's not
"mini" anymore and contains a bit more than just circular lists.
This is where other imported components are located. All files which
used to directly include ebtree were touched to update their include
path so that "import/" is now prefixed before the ebtree-related files.
The ebtree.h file was slightly adjusted to read compiler.h from the
common/ subdirectory (this is the only change).
A build issue was encountered when eb32sctree.h is loaded before
eb32tree.h because only the former checks for the latter before
defining type u32. This was addressed by adding the reverse ifdef
in eb32tree.h.
No further cleanup was done yet in order to keep changes minimal.
The blocksize and the extra field are not necessarily aligned on a
machine word. This can result in crashing an align-sensitive machine
when initializing the shctx area. Let's round both sizes up to a pointer
size to make this safe everywhere.
This fixes issue #512. This should be backported as far as 1.8.
This patch makes shctx capable of storing objects in several parts,
each parts being made of several blocks. There is no more need to
walk through until reaching the end of a row to append new blocks.
A new pointer to a struct shared_block member, named last_reserved,
has been added to struct shared_block so that to memorize the last block which was
reserved by shctx_row_reserve_hot(). Same thing about "last_append" pointer which
is used to memorize the last block used by shctx_row_data_append() to store the data.
The build breaks on a machine without openssl/crypto.h because shctx
still loads openssl-compat.h while it doesn't need it anymore since
the code was moved :
In file included from src/shctx.c:20:0:
include/proto/openssl-compat.h:3:28: fatal error: openssl/crypto.h: No such file or directory
#include <openssl/crypto.h>
Just remove include openssl-compat from shctx.
Forbid shctx to read more than expected, it allows you to use a greater
value as a len with shctx_row_data_get(), the size of the destination
buffer for example.
This patch reorganize the shctx API in a generic storage API, separating
the shared SSL session handling from its core.
The shctx API only handles the generic data part, it does not know what
kind of data you use with it.
A shared_context is a storage structure allocated in a shared memory,
allowing its usage in a multithread or a multiprocess context.
The structure use 2 linked list, one containing the available blocks,
and another for the hot locked blocks. At initialization the available
list is filled with <maxblocks> blocks of size <blocksize>. An <extra>
space is initialized outside the list in case you need some specific
storage.
+-----------------------+--------+--------+--------+--------+----
| struct shared_context | extra | block1 | block2 | block3 | ...
+-----------------------+--------+--------+--------+--------+----
<-------- maxblocks --------->
* blocksize
The API allows to store content on several linked blocks. For example,
if you allocated blocks of 16 bytes, and you want to store an object of
60 bytes, the object will be allocated in a row of 4 blocks.
The API was made for LRU usage, each time you get an object, it pushes
the object at the end of the list. When it needs more space, it discards
The functions name have been renamed in a more logical way, the part
regarding shctx have been prefixed by shctx_ and the functions for the
shared ssl session cache have been prefixed by sh_ssl_sess_.
Move the ssl callback functions of the ssl shared session cache to
ssl_sock.c. The shctx functions still needs to be separated of the ssl
tree and data.
In the last release a lot of the structures have become opaque for an
end user. This means the code using these needs to be changed to use the
proper functions to interact with these structures instead of trying to
manipulate them directly.
This does not fix any deprecations yet that are part of 1.1.0, it only
ensures that it can be compiled against that version and is still
compatible with older ones.
[wt: openssl-0.9.8 doesn't build with it, there are conflicts on certain
function prototypes which we declare as inline here and which are
defined differently there. But openssl-0.9.8 is not supported anymore
so probably it's OK to go without it for now and we'll see later if
some users still need it. Emeric has reviewed this change and didn't
spot anything obvious which requires special care. Let's try it for
real now]
In C89, "void *" is automatically promoted to any pointer type. Casting
the result of malloc/calloc to the type of the LHS variable is therefore
unneeded.
Most of this patch was built using this Coccinelle patch:
@@
type T;
@@
- (T *)
(\(lua_touserdata\|malloc\|calloc\|SSL_get_app_data\|hlua_checkudata\|lua_newuserdata\)(...))
@@
type T;
T *x;
void *data;
@@
x =
- (T *)
data
@@
type T;
T *x;
T *data;
@@
x =
- (T *)
data
Unfortunately, either Coccinelle or I is too limited to detect situation
where a complex RHS expression is of type "void *" and therefore casting
is not needed. Those cases were manually examined and corrected.
One important aspect of SSL performance tuning is the cache size,
but there's no metric to know whether it's large enough or not. This
commit introduces two counters, one for the cache lookups and another
one for cache misses. These counters are reported on "show info" on
the stats socket. This way, it suffices to see the cache misses
counter constantly grow to know that a larger cache could possibly
help.
Prevously pthread process shared lock were used by default,
if USE_SYSCALL_FUTEX is not specified.
This patch implements an OS independant kind of lock:
An active spinlock is usedf if USE_SYSCALL_FUTEX is not specified.
The old behavior is still available if USE_PTHREAD_PSHARED=1.
Process shared mutex seems not supported on some OSs (FreeBSD).
This patch checks errors on mutex lock init to fallback
on a private session cache (per process cache) in error cases.
Sessions using client certs are huge (more than 1 kB) and do not fit
in session cache, or require a huge cache.
In this new implementation sshcachesize set a number of available blocks
instead a number of available sessions.
Each block is large enough (128 bytes) to store a simple session (without
client certs).
Huge sessions will take multiple blocks depending on client certificate size.
Note: some unused code for session sync with remote peers was temporarily
removed.
It removes dependencies with futex or mutex but ssl performances decrease
using nbproc > 1 because switching process force session renegotiation.
This can be useful on small systems which never intend to run in multi-process
mode.
We don't needa to lock the memory when there is a single process. This can
make a difference on small systems where locking is much more expensive than
just a test.
FreeBSD uses the former, Linux uses the latter but generally also
defines the former as an alias of the latter. Just checked on other
OSes and AIX defines both. So better use MAP_ANON which seems to be
more commonly defined.
On RHEL/CentOS, linux/futex.h uses an u32 type which is never declared
anywhere. Let's set it with a #define in order to fix the issue without
causing conflicts with possible typedefs on other platforms.
