it (either async or sync drain).
At this moment the only user of drain is TCP, but TCP wouldn't reschedule a
callout after it has drained it, since it drains only when a tcpcb is closed.
This for now the problem isn't observed.
Submitted by: rrs
callout_when(9). See the man page update for the description of the
intended use.
Tested by: pho
Reviewed by: jhb, bjk (man page updates)
Sponsored by: The FreeBSD Foundation
MFC after: 1 month
X-Differential revision: https://reviews.freebsd.org/D7137
fixes that I think closes up the races Gleb was
looking for. This is running quite nicely in Netflix and
now no longer causes TCP-tcb leaks.
Differential Revision: 7135
not scheduled -> scheduled -> running -> not scheduled. The API and the
manual page assume that, some comments in the code assume that, and looks
like some contributors to the code also did. The problem is that this
paradigm isn't true. A callout can be scheduled and running at the same
time, which makes API description ambigouous. In such case callout_stop()
family of functions/macros should return 1 and 0 at the same time, since it
successfully unscheduled future callout but the current one is running.
Before this change we returned 1 in such a case, with an exception that
if running callout was migrating we returned 0, unless CS_MIGRBLOCK was
specified.
With this change, we now return 0 in case if future callout was unscheduled,
but another one is still in action, indicating to API users that resources
are not yet safe to be freed.
However, the sleepqueue code relies on getting 1 return code in that case,
and there already was CS_MIGRBLOCK flag, that covered one of the edge cases.
In the new return path we will also use this flag, to keep sleepqueue safe.
Since the flag CS_MIGRBLOCK doesn't block migration and now isn't limited to
migration edge case, rename it to CS_EXECUTING.
This change fixes panics on a high loaded TCP server.
Reviewed by: jch, hselasky, rrs, kib
Approved by: re (gjb)
Differential Revision: https://reviews.freebsd.org/D7042
panic string again if set, in case it scrolled out of the active
window. This avoids having to remember the symbol name.
Also add a show callout <addr> command to DDB in order to inspect
some struct callout fields in case of panics in the callout code.
This may help to see if there was memory corruption or to further
ease debugging problems.
Obtained from: projects/vnet
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Reviewed by: jhb (comment only on the show panic initally)
Differential Revision: https://reviews.freebsd.org/D4527
but next invocation is cancelled while migrating,
sleepq_check_timeout() needs to be informed that the callout is
stopped. Otherwise the thread switches off CPU and never become
runnable, since running callout could have already raced with us,
while the migrating and cancelled callout could be one which is
expected to set TDP_TIMOFAIL flag for us. This contradicts with the
expected behaviour of callout_stop() for other callers, which
e.g. decrement references from the callout callbacks.
Add a new flag CS_MIGRBLOCK requesting report of the situation as
'successfully stopped'.
Reviewed by: jhb (previous version)
Tested by: cognet, pho
PR: 200992
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D5221
- Use SDT_PROBE<N>() instead of SDT_PROBE(). This has no functional effect
at the moment, but will be needed for some future changes.
- Don't hardcode the module component of the probe identifier. This is
set automatically by the SDT framework.
MFC after: 1 week
should be used by TCP for sure in its cleanup of the IN-PCB (will be coming shortly).
Sponsored by: Netflix Inc.
Differential Revision: https://reviews.freebsd.org/D4076
SDT_PROBE requires 5 parameters whereas SDT_PROBE<n> requires n parameters
where n is typically smaller than 5.
Perhaps SDT_PROBE should be made a private implementation detail.
MFC after: 20 days
branch.
This function is used to drain a callout via a callback instead of
blocking the caller until the drain is complete. Refer to the
callout_drain_async() manual page for a detailed description.
Limitation: If a lock is used with the callout, the callout can only
be drained asynchronously one time unless the callout_init_mtx()
function is called again. This limitation is not present in
projects/hps_head and will require more invasive changes to the
timeout code, which was not in the scope of this patch.
Differential Revision: https://reviews.freebsd.org/D3521
Reviewed by: wblock
MFC after: 1 month
The typo was introduced in r278469 / 344ecf88af.
As a result of the bug there was a timing window where callout_reset()
would fail to cancel a concurrent execution of a callout that is about
to start and would schedule the callout again.
The callout would fire more times than it is scheduled.
That would happen even if the callout is initialized with a lock.
For example, the bug triggered the "Stray timeout" assertion in
taskqueue_timeout_func().
MFC after: 5 days
it helps only the TCP timers callout(9) usage. As the benefit for
others callout(9) usages did not reach a consensus the historical
usage should prevail.
Differential Revision: https://reviews.freebsd.org/D3078
being serviced return 0 (fail) but it is applicable only
mpsafe callouts. Thanks to hselasky for finding this.
Differential Revision: https://reviews.freebsd.org/D3078 (Updated)
Submitted by: hselasky
Reviewed by: jch
being serviced and indeed unstoppable.
A scenario to reproduce this case is:
- the callout is being serviced and at same time,
- callout_reset() is called on this callout that sets
the CALLOUT_PENDING flag and at same time,
- callout_stop() is called on this callout and returns 1 (success)
even if the callout is indeed currently running and unstoppable.
This issue was caught up while making r284245 (D2763) workaround, and
was discussed at BSDCan 2015. Once applied the r284245 workaround
is not needed anymore and will be reverted.
Differential Revision: https://reviews.freebsd.org/D3078
Reviewed by: jhb
Sponsored by: Verisign, Inc.
CPU, also add protection against invalid CPU's as well as
split c_flags and c_iflags so that if a user plays with the active
flag (the one expected to be played with by callers in MPSAFE) without
a lock, it won't adversely affect the callout system by causing a corrupt
list. This also means that all callers need to use the macros and *not*
play with the falgs directly (like netgraph used to).
Differential Revision: htts://reviews.freebsd.org/D1894
Reviewed by: .. timed out but looked at by jhb, imp, adrian hselasky
tested by hiren and netflix.
Sponsored by: Netflix Inc.
code in my last commit. The cc_exec_next is used to track the next
when a direct call is being made from callout. It is *never* used
in the in-direct method. When macro-izing I made it so that it
would separate out direct/vs/non-direct. This is incorrect and can
cause panics as Peter Holm has found for me (Thanks so much Peter for
all your help in this). What this change does is restore that behavior
but also get rid of the cc_next from the array and instead make it
be part of the base callout structure. This way no one else will get
confused since we will never use it for non-direct.
Reviewed by: Peter Holm and more importantly tested by him ;-)
MFC after: 3 days.
Sponsored by: Netflix Inc.
is being done in the callout code and harmonizes the macro
use.:
1) The callout_active() will lie. Basically if a migration
is occuring and the callout is about to expire and the
migration has been deferred, the callout_active will no
longer return true until after the migration. This confuses
and breaks callers that are doing callout_init(&c, 1); such
as TCP.
2) The migration code had a bug in it where when migrating, if
a two calls to callout_reset came in and they both collided with
the callout on the wheel about to run, then the second call to
callout_reset would corrupt the list the callout wheel uses
putting the callout thread into a endless loop.
3) Per imp, I have fixed all the macro occurance in the code that
were for the most part being ignored.
Phabricator D1711 and looked at by lstewart and jhb and sbruno.
Reviewed by: kostikbel, imp, adrian, hselasky
MFC after: 3 days
Sponsored by: Netflix Inc.
being held before sleeping.
This has bitten me (in ath(4)) once before and I'd like to see this
not bite anyone else.
Differential Revision: D1638
Reviewed by: jhb, hselasky
MFC after: 1 week
FreeBSD developers need more time to review patches in the surrounding
areas like the TCP stack which are using MPSAFE callouts to restore
distribution of callouts on multiple CPUs.
Bump the __FreeBSD_version instead of reverting it.
Suggested by: kmacy, adrian, glebius and kib
Differential Revision: https://reviews.freebsd.org/D1438
- Close a migration race where callout_reset() failed to set the
CALLOUT_ACTIVE flag.
- Callout callback functions are now allowed to be protected by
spinlocks.
- Switching the callout CPU number cannot always be done on a
per-callout basis. See the updated timeout(9) manual page for more
information.
- The timeout(9) manual page has been updated to reflect how all the
functions inside the callout API are working. The manual page has
been made function oriented to make it easier to deduce how each of
the functions making up the callout API are working without having
to first read the whole manual page. Group all functions into a
handful of sections which should give a quick top-level overview
when the different functions should be used.
- The CALLOUT_SHAREDLOCK flag and its functionality has been removed
to reduce the complexity in the callout code and to avoid problems
about atomically stopping callouts via callout_stop(). If someone
needs it, it can be re-added. From my quick grep there are no
CALLOUT_SHAREDLOCK clients in the kernel.
- A new callout API function named "callout_drain_async()" has been
added. See the updated timeout(9) manual page for a complete
description.
- Update the callout clients in the "kern/" folder to use the callout
API properly, like cv_timedwait(). Previously there was some custom
sleepqueue code in the callout subsystem, which has been removed,
because we now allow callouts to be protected by spinlocks. This
allows us to tear down the callout like done with regular mutexes,
and a "td_slpmutex" has been added to "struct thread" to atomically
teardown the "td_slpcallout". Further the "TDF_TIMOFAIL" and
"SWT_SLEEPQTIMO" states can now be completely removed. Currently
they are marked as available and will be cleaned up in a follow up
commit.
- Bump the __FreeBSD_version to indicate kernel modules need
recompilation.
- There has been several reports that this patch "seems to squash a
serious bug leading to a callout timeout and panic".
Kernel build testing: all architectures were built
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D1438
Sponsored by: Mellanox Technologies
Reviewed by: jhb, adrian, sbruno and emaste
a running event each time it executes a callout function. The event
includes the function pointer, argument, and whether or not it was run from
hardware interrupt context. The callwheel is marked idle when each handler
completes. This effectively logs the duration of each callout routine in
the graph.
These changes prevent sysctl(8) from returning proper output,
such as:
1) no output from sysctl(8)
2) erroneously returning ENOMEM with tools like truss(1)
or uname(1)
truss: can not get etype: Cannot allocate memory
there is an environment variable which shall initialize the SYSCTL
during early boot. This works for all SYSCTL types both statically and
dynamically created ones, except for the SYSCTL NODE type and SYSCTLs
which belong to VNETs. A new flag, CTLFLAG_NOFETCH, has been added to
be used in the case a tunable sysctl has a custom initialisation
function allowing the sysctl to still be marked as a tunable. The
kernel SYSCTL API is mostly the same, with a few exceptions for some
special operations like iterating childrens of a static/extern SYSCTL
node. This operation should probably be made into a factored out
common macro, hence some device drivers use this. The reason for
changing the SYSCTL API was the need for a SYSCTL parent OID pointer
and not only the SYSCTL parent OID list pointer in order to quickly
generate the sysctl path. The motivation behind this patch is to avoid
parameter loading cludges inside the OFED driver subsystem. Instead of
adding special code to the OFED driver subsystem to post-load tunables
into dynamically created sysctls, we generalize this in the kernel.
Other changes:
- Corrected a possibly incorrect sysctl name from "hw.cbb.intr_mask"
to "hw.pcic.intr_mask".
- Removed redundant TUNABLE statements throughout the kernel.
- Some minor code rewrites in connection to removing not needed
TUNABLE statements.
- Added a missing SYSCTL_DECL().
- Wrapped two very long lines.
- Avoid malloc()/free() inside sysctl string handling, in case it is
called to initialize a sysctl from a tunable, hence malloc()/free() is
not ready when sysctls from the sysctl dataset are registered.
- Bumped FreeBSD version to indicate SYSCTL API change.
MFC after: 2 weeks
Sponsored by: Mellanox Technologies
Under enough load, the swi's can actually be preempted and migrated
to other currently free cores. When doing RSS experiments, this lead
to the per-CPU TCP timers not lining up any more with the RX CPU said
flows were ending up on, leading to increased lock contention.
Since there was a little pushback on flipping them on by default,
I've left the default at "don't pin."
The other less obvious problem here is that the default swi
is also the same as the destination swi for CPU #0. So if one
pins the swi on CPU #0, there's no default floating swi.
A nice future project would be to create a separate swi for
the "default" floating swi, as well as per-CPU swis that are
(optionally) pinned.
Tested:
* parallel TCP tests (2 x 1g unfortunately for now);
CPU: Intel(R) Xeon(R) CPU E5-2650
Note:
This is based on some initial investigation into RSS/TCP stack lock
contention on FreeBSD-HEAD whilst at Netflix in January 2014.
SBT_MAX, to make it more robust in case internal type representation will
change in the future. All the consumers were migrated to SBT_MAX and
every new consumer (if any) should from now use this interface.
Requested by: bapt, jmg, Ryan Lortie (implictly)
Reviewed by: mav, bde
In its stead use the Solaris / illumos approach of emulating '-' (dash)
in probe names with '__' (two consecutive underscores).
Reviewed by: markj
MFC after: 3 weeks
option, unbreak the lock tracing release semantic by embedding
calls to LOCKSTAT_PROFILE_RELEASE_LOCK() direclty in the inlined
version of the releasing functions for mutex, rwlock and sxlock.
Failing to do so skips the lockstat_probe_func invokation for
unlocking.
- As part of the LOCKSTAT support is inlined in mutex operation, for
kernel compiled without lock debugging options, potentially every
consumer must be compiled including opt_kdtrace.h.
Fix this by moving KDTRACE_HOOKS into opt_global.h and remove the
dependency by opt_kdtrace.h for all files, as now only KDTRACE_FRAMES
is linked there and it is only used as a compile-time stub [0].
[0] immediately shows some new bug as DTRACE-derived support for debug
in sfxge is broken and it was never really tested. As it was not
including correctly opt_kdtrace.h before it was never enabled so it
was kept broken for a while. Fix this by using a protection stub,
leaving sfxge driver authors the responsibility for fixing it
appropriately [1].
Sponsored by: EMC / Isilon storage division
Discussed with: rstone
[0] Reported by: rstone
[1] Discussed with: philip
Without these, if the timeout value passed is "large enough", the
value of the sum of it and other factors (e.g. current time as
returned by sbinuptime() or 'precision' argument) might result in a
negative number. This negative number is then passed to
eventtimers(4), which causes et_start() routine to load et_min_period
into eventtimer, making the CPU where the thread is stuck forever in
timer interrupt handler routine. This is now avoided rounding to
INT64_MAX the timeout period in case of overflow.
Reported by: kib, pho
Discussed with: kib, mav
Tested by: pho (stress2 suite, kevent7.sh scenario)
Approved by: re (kib)
rm_priotracker' directly in the softclock thread. Now consumers can
pass CALLOUT_SHAREDLOCK flag to callout initialization routine safely.
The choice of the already existing flags instead of special casing
shared rmlocks is done to prevent consumer footshooting.
Suggested by: jhb
Reviewed by: jhb
Approved by: re (delphij)
