| Age | Commit message (Collapse) | Author |
|---|
|
This fixes a race between 1) sweeping and freeing an unmarked large
span and 2) reusing that span and allocating from it. This race arises
because mSpan_Sweep returns spans for large objects to the heap
*before* heapBitsSweepSpan clears the mark bit on the object in the
span.
Specifically, the following sequence of events can lead to an
incorrectly zeroed bitmap byte, which causes the garbage collector to
not trace any pointers in that object (the pointer bits for the first
four words are cleared, and the scan bits are also cleared, so it
looks like a no-scan object).
1) P0 calls mSpan_Sweep on a large span S0 with an unmarked object on it.
2) mSpan_Sweep calls heapBitsSweepSpan, which invokes the callback for
the one (unmarked) object on the span.
3) The callback calls mHeap_Free, which makes span S0 available for
allocation, but this is too early.
4) P1 grabs this S0 from the heap to use for allocation.
5) P1 allocates an object on this span and writes that object's type
bits to the bitmap.
6) P0 returns from the callback to heapBitsSweepSpan.
heapBitsSweepSpan clears the byte containing the mark, even though
this span is now owned by P1 and this byte contains important
bitmap information.
This fixes this problem by simply delaying the mHeap_Free until after
the heapBitsSweepSpan. I think the overall logic of mSpan_Sweep could
be simplified now, but this seems like the minimal change.
Fixes #11617.
Change-Id: I6b1382c7e7cc35f81984467c0772fe9848b7522a
Reviewed-on: https://go-review.googlesource.com/12320
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Rob Pike <r@golang.org>
|
|
Broke arm64. Update #9880.
This reverts commit 38d9b2a3a942892193195a6912ab23cdaff23e20.
Change-Id: I35fa21005af2183828a9d8b195ebcfbe45ec5138
Reviewed-on: https://go-review.googlesource.com/12247
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Running a safe-point function on syscall entry uses systemstack() and
hence clobbers g.sched.pc and g.sched.sp. Fix this by re-saving them
after the systemstack, just like in the other uses of systemstack in
reentersyscall.
Change-Id: I47868a53eba24d81919fda56ef6bbcf72f1f922e
Reviewed-on: https://go-review.googlesource.com/12125
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Currently, we run a P's safe-point function immediately after entering
_Psyscall state. This is unsafe, since as soon as we put the P in
_Psyscall, we no longer control the P and another M may claim it.
We'll still run the safe-point function only once (because doing so
races on an atomic), but the P may no longer be at a safe-point when
we do so.
In particular, this means that the use of forEachP to dispose all P's
gcw caches is unsafe. A P may enter a syscall, run the safe-point
function, and dispose the P's gcw cache concurrently with another M
claiming the P and attempting to use its gcw cache. If this happens,
we may empty the gcw's workbuf after putting it on
work.{full,partial}, or add pointers to it after putting it in
work.empty. This will cause an assertion failure when we later pop the
workbuf from the list and its object count is inconsistent with the
list we got it from.
Fix this by running the safe-point function just before putting the P
in _Psyscall.
Related to #11640. This probably fixes this issue, but while I'm able
to show that we can enter a bad safe-point state as a result of this,
I can't reproduce that specific failure.
Change-Id: I6989c8ca7ef2a4a941ae1931e9a0748cbbb59434
Reviewed-on: https://go-review.googlesource.com/12124
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Change-Id: I945d46d3bb63f1992bce0d0b1e89e75cac9bbd54
Reviewed-on: https://go-review.googlesource.com/12271
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
|
|
For #9880. Let's see what breaks.
Change-Id: Ic8b99a604e60177a448af5f7173595feed607875
Reviewed-on: https://go-review.googlesource.com/10818
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
|
|
Fixes #11656 (again).
Change-Id: I170ff10bfbdb0f34e57c11de42b6ee5291837813
Reviewed-on: https://go-review.googlesource.com/12142
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
These memstats are currently being computed by gcMark, which was
appropriate in Go 1.4, but gcMark is now just one part of a bigger
picture. In particular, it can't account for the sweep termination
pause time, it can't account for all of the mark termination pause
time, and the reported "pause end" and "last GC" times will be
slightly earlier than they really are.
Lift computing of these statistics into func gc, which has the
appropriate visibility into the process to compute them correctly.
Fixes one of the issues in #10323. This does not add new statistics
appropriate to the concurrent collector; it simply fixes existing
statistics that are being misreported.
Change-Id: I670cb16594a8641f6b27acf4472db15b6e8e086e
Reviewed-on: https://go-review.googlesource.com/11794
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Currently we report MemStats.PauseEnd in nanoseconds, but with no
particular 0 time. On Linux, the 0 time is when the host started. On
Darwin, it's the UNIX epoch. This is also inconsistent with the other
absolute time in MemStats, LastGC, which is always reported in
nanoseconds since 1970.
Fix PauseEnd so it's always reported in nanoseconds since 1970, like
LastGC.
Fixes one of the issues raised in #10323.
Change-Id: Ie2fe3169d45113992363a03b764f4e6c47e5c6a8
Reviewed-on: https://go-review.googlesource.com/11801
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Fixes #11656.
Change-Id: Ib81d583e4b004e67dc9d2f898fd798112434e7a9
Reviewed-on: https://go-review.googlesource.com/12026
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
|
|
Fixes race detector build.
Change-Id: I8bdc78d57487580e6b5b8c415df4653a1ba69e37
Reviewed-on: https://go-review.googlesource.com/12087
Reviewed-by: Austin Clements <austin@google.com>
|
|
Missed select case when adding the barrier last time.
All the more reason to refactor this code in Go 1.6.
Fixes #11643.
Change-Id: Ib0d19d6e0939296c0a3e06dda5e9b76f813bbc7e
Reviewed-on: https://go-review.googlesource.com/12086
Reviewed-by: Austin Clements <austin@google.com>
|
|
The one in misc/makerelease/makerelease.go is particularly bad and
probably warrants rotating our keys.
I didn't update old weekly notes, and reverted some changes involving
test code for now, since we're late in the Go 1.5 freeze. Otherwise,
the rest are all auto-generated changes, and all manually reviewed.
Change-Id: Ia2753576ab5d64826a167d259f48a2f50508792d
Reviewed-on: https://go-review.googlesource.com/12048
Reviewed-by: Rob Pike <r@golang.org>
|
|
The default behaviour for fatal errors and runtime panics is to dump
the goroutine stack traces and exit with code 2. However, when the process is
owned by foreign code, it is suprising and inappropriate to suddenly exit
the whole process, even on fatal errors. Instead, re-use the crash behaviour
from GOTRACEBACK=crash and abort.
The motivating use case is issue #11382, where an Android crash reporter
is confused by an exiting process, but I believe the aborting behaviour
is appropriate for all cases where Go does not own the process.
The change is simple and contained and will enable reliable crash reporting
for Android apps in Go 1.5, but I'll leave it to others to judge whether it
is too late for Go 1.5.
Fixes #11382
Change-Id: I477328e1092f483591c99da1fbb8bc4411911785
Reviewed-on: https://go-review.googlesource.com/12032
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
|
|
Recent change (CL 10370) unexpectedly broke TestRaiseException on
Windows XP amd64. I still do not know why. But reverting old
CL 8165 fixes the problem.
This effectively makes Windows XP amd64 use AddVectoredContinueHandler
instead of SetUnhandledExceptionFilter for exception handling. That is
what we do for all recent Windows versions too.
Fixes #11481
Change-Id: If2e8037711f05bf97e3c69f5a8d86af67c58f6fc
Reviewed-on: https://go-review.googlesource.com/11888
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Daniel Theophanes <kardianos@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
|
|
When GOROOT_FINAL is set when running all.bash, the tests are run
before the files are copied to GOROOT_FINAL. The tests are run with
GOROOT set, so most work fine. This fixes two cases that do not.
In cmd/go/go_test.go we were explicitly removing GOROOT from the
environment, causing tests that did not themselves explicitly set
GOROOT to fail. There was no need to explicitly remove GOROOT, so
don't do it. If people choose to run "go test cmd/go" with a bad
GOROOT, that is their own lookout.
In the runtime GDB test, the linker has told gdb to find the support
script in GOROOT_FINAL, which will fail. Check for that case, and
skip the test when we see it.
Fixes #11652.
Change-Id: I4d3a32311e3973c30fd8a79551aaeab6789d0451
Reviewed-on: https://go-review.googlesource.com/12021
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
|
|
Update #11609.
Change-Id: Ie363facf13f5e62f1af4a8bdc42a18fb36e16ebf
Reviewed-on: https://go-review.googlesource.com/12022
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
|
|
sysmon triggers a GC if there has been no GC for two minutes.
Currently, this is a STW GC. There is no reason for this to be STW, so
make it concurrent.
Fixes #10261.
Change-Id: I92f3ac37272d5c2a31480ff1fa897ebad08775a9
Reviewed-on: https://go-review.googlesource.com/11955
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
The expansion of structure, array, slice, and map literals
does not use the right line number in its introduced assignments
to temporaries, which leads to incorrect line number attribution
for expressions in those literals.
Inlining also incorrectly replaced the line numbers of args to
inlined functions.
This was revealed in CL 9721 because a now-avoided temporary
assignment introduced the correct line number.
I.e. before CL 9721
"tmp_wrongline := expr"
was transformed to
"tmp_rightline := expr; tmp_wrongline := tmp_rightline"
Also includes a repair to CL 10334 involving line numbers
where a spurious -1 remained (should have been 0, now is 0).
Fixes #11400.
Change-Id: I3a4687efe463977fa1e2c996606f4d91aaf22722
Reviewed-on: https://go-review.googlesource.com/11730
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Sameer Ajmani <sameer@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Basic randomization of goroutine scheduling for -race mode.
It is probably possible to do much better (there's a paper linked
in the issue that I haven't read, for example), but this suffices
to introduce at least some unpredictability into the scheduling order.
The goal here is to have _something_ for Go 1.5, so that we don't
start hitting more of these scheduling order-dependent bugs
if we change the scheduler order again in Go 1.6.
For #11372.
Change-Id: Idf1154123fbd5b7a1ee4d339e93f97635cc2bacb
Reviewed-on: https://go-review.googlesource.com/11795
Reviewed-by: Austin Clements <austin@google.com>
|
|
Fixes #7561 correctly.
Fixes #9137.
Change-Id: I7f27e199d7101b785a7645f789e8fe41a405a86f
Reviewed-on: https://go-review.googlesource.com/11713
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
|
|
Change-Id: I08de33aacb3fc932722286d69b1dd70ffe787c89
Reviewed-on: https://go-review.googlesource.com/11697
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
The old code was recording the current table output offset,
so the table from the next function would be used instead of
the runtime realizing that there was no table at all.
Add debug constant in runtime to check this for every function
at startup. It's too expensive to do that by default, but we can
do the last five functions. The end of the table is usually where
the C symbols end up, so that's where the problems typically are.
Fixes #10747.
Fixes #11396.
Change-Id: I13592e78017969fc22979fa902e19e1b151d41b1
Reviewed-on: https://go-review.googlesource.com/11657
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
|
|
Currently we fail to reset the live heap accounting state before the
checkmark mark and before the gctrace=2 extra mark. As a result, if
either are enabled, at the end of GC it thinks there are 0 bytes of
live heap, which causes the GC controller to initiate a new GC
immediately, regardless of the true heap size.
Fix this by factoring this state reset into a function and calling it
before all three possible marks.
This function should be merged with gcResetGState, but doing so
requires some additional cleanup, so it will wait for after the
freeze. Filed #11427 for this cleanup.
Fixes #10492.
Change-Id: Ibe46348916fc8368fac6f086e142815c970a6f4d
Reviewed-on: https://go-review.googlesource.com/11561
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Memory for stacks is manually managed by the runtime and, currently
(with one exception) we free stack spans immediately when the last
stack on a span is freed. However, the garbage collector assumes that
spans can never transition from non-free to free during scan or mark.
This disagreement makes it possible for the garbage collector to mark
uninitialized objects and is blocking us from re-enabling the bad
pointer test in the garbage collector (issue #9880).
For example, the following sequence will result in marking an
uninitialized object:
1. scanobject loads a pointer slot out of the object it's scanning.
This happens to be one of the special pointers from the heap into a
stack. Call the pointer p and suppose it points into X's stack.
2. X, running on another thread, grows its stack and frees its old
stack.
3. The old stack happens to be large or was the last stack in its
span, so X frees this span, setting it to state _MSpanFree.
4. The span gets reused as a heap span.
5. scanobject calls heapBitsForObject, which loads the span containing
p, which is now in state _MSpanInUse, but doesn't necessarily have
an object at p. The not-object at p gets marked, and at this point
all sorts of things can go wrong.
We already have a partial solution to this. When shrinking a stack, we
put the old stack on a queue to be freed at the end of garbage
collection. This was done to address exactly this problem, but wasn't
a complete solution.
This commit generalizes this solution to both shrinking and growing
stacks. For stacks that fit in the stack pool, we simply don't free
the span, even if its reference count reaches zero. It's fine to reuse
the span for other stacks, and this enables that. At the end of GC, we
sweep for cached stack spans with a zero reference count and free
them. For larger stacks, we simply queue the stack span to be freed at
the end of GC. Ideally, we would reuse these large stack spans the way
we can small stack spans, but that's a more invasive change that will
have to wait until after the freeze.
Fixes #11267.
Change-Id: Ib7f2c5da4845cc0268e8dc098b08465116972a71
Reviewed-on: https://go-review.googlesource.com/11502
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
We don't use this state. _GCoff means we're sweeping in the
background. This makes it clear in the next commit that _GCoff and
only _GCoff means sweeping.
Change-Id: I416324a829ba0be3794a6cf3cf1655114cb6e47c
Reviewed-on: https://go-review.googlesource.com/11501
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Currently the runtime fails to clear a G's stack barriers in gfput if
the G's stack allocation is _FixedStack bytes. This causes the runtime
to panic if the following sequence of events happens:
1) The runtime installs stack barriers on a G.
2) The G exits by calling runtime.Goexit. Since this does not
necessarily return through the stack barriers installed on the G,
there may still be untriggered stack barriers left on the G's stack
in recorded in g.stkbar.
3) The runtime calls gfput to add the exiting G to the free pool. If
the G's stack allocation is _FixedStack bytes, we fail to clear
g.stkbar.
4) A new G starts and allocates the G that was just added to the free
pool.
5) The new G begins to execute and overwrites the stack slots that had
stack barriers in them.
6) The garbage collector enters mark termination, attempts to remove
stack barriers from the new G, and finds that they've been
overwritten.
Fix this by clearing the stack barriers in gfput in the case where it
reuses the stack.
Fixes #11256.
Change-Id: I377c44258900e6bcc2d4b3451845814a8eeb2bcf
Reviewed-on: https://go-review.googlesource.com/11461
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Stack can move during callback, so libcall struct cannot be stored on stack.
asmstdcall updates return values and errno in libcall struct parameter, but
these could be at different location when callback returns.
Store these in m, so they are not affected by GC.
Fixes #10406
Change-Id: Id01c9d2b4b44530494e6d9e9e1c875261ce477cd
Reviewed-on: https://go-review.googlesource.com/10370
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Currently, to write out the bitmap of a slice of a type with a GCprog,
we construct a new GCprog that executes the underlying type's GCprog
to write out the bitmap once and then repeats those bits n more times.
This results in n+1 repetitions of the bitmap, which is one more
repetition than it should be. This corrupts the bitmap of the heap
following the slice and may write past the mapped bitmap memory and
segfault.
Fix this by repeating the bitmap only n-1 more times.
Fixes #11430.
Change-Id: Ic24854363bffc5a755b66f257339f9309ada3aa5
Reviewed-on: https://go-review.googlesource.com/11570
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
|
|
These tests pass after cl/11417.
Change-Id: Id98088c52e564208ce432e9717eddd672c42c66d
Reviewed-on: https://go-review.googlesource.com/11551
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Removes the remains of the old C based stepflt implementation.
Also removed goto usage.
Change-Id: Ida4742c49000fae4fea4649f28afde630ce4c577
Reviewed-on: https://go-review.googlesource.com/9600
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
The new inlined code for append assumed that it could pass the
desired new cap to growslice, not the number of new elements.
But growslice still interpreted the argument as the number of new elements,
making it always grow by >2x (more precisely, 2x+1 rounded up
to the next malloc block size). At the time, I had intended to change
the other callers to use the new cap as well, but it's too late for that.
Instead, introduce growslice_n for the old callers and keep growslice
for the inlined (common case) caller.
Fixes #11403.
Filed #11419 to merge them.
Change-Id: I1338b1e5b352f3be4e43641f44b652ef7195251b
Reviewed-on: https://go-review.googlesource.com/11541
Reviewed-by: Austin Clements <austin@google.com>
|
|
Instrument operands of OKEY.
Also instrument OSLICESTR. Previously it was not needed
because of preceeding bounds checks (which were instrumented).
But the preceeding bounds checks have disappeared.
Change-Id: I3b0de213e23cbcf5b8ef800abeded5eeeb3f8287
Reviewed-on: https://go-review.googlesource.com/11417
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Change-Id: Ifb8e4e13c7778a7c0113190051415e096f5db94f
Reviewed-on: https://go-review.googlesource.com/11390
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Andrew Gerrand <adg@golang.org>
|
|
At some point it silently stopped recognizing test output.
Meanwhile two tests degraded...
Change-Id: I90a0325fc9aaa16c3ef16b9c4c642581da2bb10c
Reviewed-on: https://go-review.googlesource.com/11416
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
|
|
For debuggers and other program inspectors.
Fixes #9914.
Change-Id: I670728cea28c045e6eaba1808c550ee2f34d16ff
Reviewed-on: https://go-review.googlesource.com/11341
Reviewed-by: Austin Clements <austin@google.com>
|
|
The test is flaky on builders lately. I don't see any issues other than
usage of very small sleeps. So increase the sleeps. Also take opportunity
to refactor the code.
On my machine this change significantly reduces failure rate with GOMAXPROCS=2.
I can't reproduce the failure with GOMAXPROCS=1.
Fixes #10726
Change-Id: Iea6f10cf3ce1be5c112a2375d51c13687a8ab4c9
Reviewed-on: https://go-review.googlesource.com/9803
Reviewed-by: Austin Clements <austin@google.com>
|
|
When heapBitsSetType repeats a source bitmap with a scalar tail
(typ.ptrdata < typ.size), it lays out the tail upon reaching the end
of the source bitmap by simply increasing the number of bits claimed
to be in the incoming bit buffer. This causes later iterations to read
the appropriate number of zeros out of the bit buffer before starting
on the next repeat of the source bitmap.
Currently, however, later iterations of the loop continue to read bits
from the source bitmap *regardless of the number of bits currently in
the bit buffer*. The bit buffer can only hold 32 or 64 bits, so if the
scalar tail is large and the padding bits exceed the size of the bit
buffer, the read from the source bitmap on the next iteration will
shift the incoming bits into oblivion when it attempts to put them in
the bit buffer. When the buffer does eventually shift down to where
these bits were supposed to be, it will contain zeros. As a result,
words that should be marked as pointers on later repetitions are
marked as scalars, so the garbage collector does not trace them. If
this is the only reference to an object, it will be incorrectly freed.
Fix this by adding logic to drain the bit buffer down if it is large
instead of reading more bits from the source bitmap.
Fixes #11286.
Change-Id: I964432c4b9f1cec334fc8c3da0ff16460203feb6
Reviewed-on: https://go-review.googlesource.com/11360
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
h_spans can be accessed concurrently without synchronization from
other threads, which means it needs the appropriate memory barriers on
weakly ordered machines. It happens to already have the necessary
memory barriers because all accesses to h_spans are currently
protected by the heap lock and the unlocks happen in exactly the
places where release barriers are needed, but it's easy to imagine
that this could change in the future. Document the fact that we're
depending on the barrier implied by the unlock.
Related to issue #9984.
Change-Id: I1bc3c95cd73361b041c8c95cd4bb92daf8c1f94a
Reviewed-on: https://go-review.googlesource.com/11361
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
|
|
This CL removes the single and racy use of mheap.arena_end outside
of the bookkeeping done in mHeap_init and mHeap_Alloc.
There should be no way for heapBitsForSpan to see a pointer to
an invalid span. This CL makes the check for this more precise by
checking that the pointer is between mheap_.arena_start and
mheap_.arena_used instead of mheap_.arena_end.
Change-Id: I1200b54353ee1eda002d92645fd8d26048600ceb
Reviewed-on: https://go-review.googlesource.com/11342
Reviewed-by: Austin Clements <austin@google.com>
|
|
In order to avoid a race with a concurrent write barrier or garbage
collector thread, any update to arena_used must be preceded by mapping
the corresponding heap bitmap and spans array memory. Otherwise, the
concurrent access may observe that a pointer falls within the heap
arena, but then attempt to access unmapped memory to look up its span
or heap bits.
Commit d57c889 fixed all of the places where we updated arena_used
immediately before mapping the heap bitmap and spans, but it missed
the one place where we update arena_used and depend on later code to
update it again and map the bitmap and spans. This creates a window
where the original race can still happen. This commit fixes this by
mapping the heap bitmap and spans before this arena_used update as
well. This code path is only taken when expanding the heap reservation
on 32-bit over a hole in the address space, so these extra mmap calls
should have negligible impact.
Fixes #10212, #11324.
Change-Id: Id67795e6c7563eb551873bc401e5cc997aaa2bd8
Reviewed-on: https://go-review.googlesource.com/11340
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
|
|
The unsynchronized accesses to mheap_.arena_used in the concurrent
part of the garbage collector look like a problem waiting to happen.
In fact, they are safe, but the reason is somewhat subtle and
undocumented. This commit documents this reasoning.
Related to issue #9984.
Change-Id: Icdbf2329c1aa11dbe2396a71eb5fc2a85bd4afd5
Reviewed-on: https://go-review.googlesource.com/11254
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
|
|
Currently its possible for the garbage collector to observe
uninitialized memory or stale heap bitmap bits on weakly ordered
architectures such as ARM and PPC. On such architectures, the stores
that zero newly allocated memory and initialize its heap bitmap may
move after a store in user code that makes the allocated object
observable by the garbage collector.
To fix this, add a "publication barrier" (also known as an "export
barrier") before returning from mallocgc. This is a store/store
barrier that ensures any write done by user code that makes the
returned object observable to the garbage collector will be ordered
after the initialization performed by mallocgc. No barrier is
necessary on the reading side because of the data dependency between
loading the pointer and loading the contents of the object.
Fixes one of the issues raised in #9984.
Change-Id: Ia3d96ad9c5fc7f4d342f5e05ec0ceae700cd17c8
Reviewed-on: https://go-review.googlesource.com/11083
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Martin Capitanio <capnm9@gmail.com>
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
Change-Id: I5917bea8bb35b0e725dcc56a68f3a70137cfc180
Reviewed-on: https://go-review.googlesource.com/9387
Reviewed-by: Ian Lance Taylor <iant@golang.org>
|
|
Some latency regressions have crept into our system over the past few
weeks. This CL fixes those by having the mark phase more aggressively
blacken objects so that the mark termination phase, a STW phase, has less
work to do. Three approaches were taken when the mark phase believes
it has no more work to do, ie all the work buffers are empty.
If things have gone well the mark phase is correct and there is
in fact little or no work. In that case the following items will
take very little time. If the mark phase is wrong this CL will
ferret that work out and give the mark phase a chance to deal with
it concurrently before mark termination begins.
When the mark phase first appears to be out of work, it does three things:
1) It switches from allocating white to allocating black to reduce the
number of unmarked objects reachable only from stacks.
2) It flushes and disables per-P GC work caches so all work must be in
globally visible work buffers.
3) It rescans the global roots---the BSS and data segments---so there
are fewer objects to blacken during mark termination. We do not rescan
stacks at this point, though that could be done in a later CL.
After these steps, it again drains the global work buffers.
On a lightly loaded machine the garbage benchmark has reduced the
number of GC cycles with latency > 10 ms from 83 out of 4083 cycles
down to 2 out of 3995 cycles. Maximum latency was reduced from
60+ msecs down to 20 ms.
Change-Id: I152285b48a7e56c5083a02e8e4485dd39c990492
Reviewed-on: https://go-review.googlesource.com/10590
Reviewed-by: Austin Clements <austin@google.com>
|
|
While we're at it, move some misplaced comment blocks around.
Change-Id: I1847d7f1ca1dbb8e5de737203c4ed6c66e112508
Reviewed-on: https://go-review.googlesource.com/10188
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
There were two issues.
1. Delayed EvGoSysExit could have been emitted during TraceStart,
while it had not yet emitted EvGoInSyscall.
2. Delayed EvGoSysExit could have been emitted during next tracing session.
Fixes #10476
Fixes #11262
Change-Id: Iab68eb31cf38eb6eb6eee427f49c5ca0865a8c64
Reviewed-on: https://go-review.googlesource.com/9132
Reviewed-by: Russ Cox <rsc@golang.org>
|
|
In preparation for rename of cgocall_errno into cgocall and
asmcgocall_errno into asmcgocall in the fllowinng CL.
rsc requested CL 9387 to be split into two parts. This is first part.
Change-Id: I7434f0e4b44dd37017540695834bfcb1eebf0b2f
Reviewed-on: https://go-review.googlesource.com/11166
Reviewed-by: Ian Lance Taylor <iant@golang.org>
|
|
Change-Id: I389b2e10fe667eaa55f87b71b1e004994694d4a3
Reviewed-on: https://go-review.googlesource.com/11173
Reviewed-by: Austin Clements <austin@google.com>
|
|
This fixes a hang during runtime.TestTraceStress.
It also fixes double-scan of stacks, which leads to
stack barrier installation failures.
Both of these have shown up as flaky failures on the dashboard.
Fixes #10941.
Change-Id: Ia2a5991ce2c9f43ba06ae1c7032f7c898dc990e0
Reviewed-on: https://go-review.googlesource.com/11089
Reviewed-by: Austin Clements <austin@google.com>
|
