Since barrier-less memclr is only safe in very narrow circumstances,
this commit renames memclr to avoid accidentally calling memclr on
typed memory. This can cause subtle, non-deterministic bugs, so it's
worth some effort to prevent. In the near term, this will also prevent
bugs creeping in from any concurrent CLs that add calls to memclr; if
this happens, whichever patch hits master second will fail to compile.
This also adds the other new memclr variants to the compiler's
builtin.go to minimize the churn on that binary blob. We'll use these
in future commits.
Updates #17503.
Change-Id: I00eead049f5bd35ca107ea525966831f3d1ed9ca
Reviewed-on: https://go-review.googlesource.com/31369
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Like h_allspans and mheap_.allspans, these were two ways of referring
to the spans array from when the runtime was split between C and Go.
Clean this up by making mheap_.spans a slice and eliminating h_spans.
Change-Id: I3aa7038d53c3a4252050aa33e468c48dfed0b70e
Reviewed-on: https://go-review.googlesource.com/30532
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently mspan.isFree technically returns whether the object was not
allocated *during this cycle*. Fix it so it actually returns whether
or not the object is allocated so the method is more generally useful
(especially for debugging).
It has one caller, which is carefully written to be insensitive to
this distinction, but this lets us simplify this caller.
Change-Id: I9d79cf784a56015e434961733093c1d8d03fc091
Reviewed-on: https://go-review.googlesource.com/30145
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Change-Id: I8fd271066925734c3f7196f64db04f27c4ce27cb
Reviewed-on: https://go-review.googlesource.com/30274
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
These used to be necessary when racing with updates to the mark bit,
but since the mark bit is no longer in the bitmap and the checkmark is
only updated with the world stopped, we can now always use regular
writes to update the type information in the heap bitmap.
Somewhat surprisingly, this has basically no overall performance
effect beyond the usual noise, but it does clean up the code.
Change-Id: I3933d0b4c0bc1c9bcf6313613515c0b496212105
Reviewed-on: https://go-review.googlesource.com/29277
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Now that the runtime fetches the true physical page size from the OS,
make the physical page size used by heap growth a variable instead of
a constant. This isn't used in any performance-critical paths, so it
shouldn't be an issue.
sys.PhysPageSize is also renamed to sys.DefaultPhysPageSize to make it
clear that it's not necessarily the true page size. There are no uses
of this constant any more, but we'll keep it around for now.
Updates #12480 and #10180.
Change-Id: I6c23b9df860db309c38c8287a703c53817754f03
Reviewed-on: https://go-review.googlesource.com/25022
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Commit 59877bf renamed bitMarked to bitScan, since the bitmap is no
longer used for marking. However, there were several other references
to this strewn about comments and in some other constant names. Fix
these up, too.
Change-Id: I4183d28c6b01977f1d75a99ad55b150f2211772d
Reviewed-on: https://go-review.googlesource.com/28450
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently the heapBitsSetType documentation says that there are no
races on the heap bitmap, but that isn't exactly true. There are no
*write-write* races, but there are read-write races. Expand the
documentation to explain this and why it's okay.
Change-Id: Ibd92b69bcd6524a40a9dd4ec82422b50831071ed
Reviewed-on: https://go-review.googlesource.com/23092
Reviewed-by: Rick Hudson <rlh@golang.org>
In issue #13992, Russ mentioned that the heap bitmap footprint was
halved but that the bitmap size calculation hadn't been updated. This
presents the opportunity to either halve the bitmap size or double
the addressable virtual space. This CL doubles the addressable virtual
space. On 32 bit this can be tweaked further to allow the bitmap to
cover the entire 4GB virtual address space, removing a failure mode
if the kernel hands out memory with a too low address.
First, fix the calculation and double _MaxArena32 to cover 4GB virtual
memory space with the same bitmap size (256 MB).
Then, allow the fallback mode for the initial memory reservation
on 32 bit (or 64 bit with too little available virtual memory) to not
include space for the arena. mheap.sysAlloc will automatically reserve
additional space when the existing arena is full.
Finally, set arena_start to 0 in 32 bit mode, so that any address is
acceptable for subsequent (additional) reservations.
Before, the bitmap was always located just before arena_start, so
fix the two places relying on that assumption: Point the otherwise unused
mheap.bitmap to one byte after the end of the bitmap, and use it for
bitmap addressing instead of arena_start.
With arena_start set to 0 on 32 bit, the cgoInRange check is no longer a
sufficient check for Go pointers. Introduce and call inHeapOrStack to
check whether a pointer is to the Go heap or stack.
While we're here, remove sysReserveHigh which seems to be unused.
Fixes#13992
Change-Id: I592b513148a50b9d3967b5c5d94b86b3ec39acc2
Reviewed-on: https://go-review.googlesource.com/20471
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This updates some comments that became out of date when we moved the
mark bit out of the heap bitmap and started using the high bit for the
first word as a scan/dead bit.
Change-Id: I4a572d16db6114cadff006825466c1f18359f2db
Reviewed-on: https://go-review.googlesource.com/22662
Reviewed-by: Rick Hudson <rlh@golang.org>
With the switch to separate mark bitmaps, the scan/dead bit for the
first word of each object is now unused. Reclaim this bit and use it
as a scan/dead bit, just like words three and on. The second word is
still used for checkmark.
This dramatically simplifies heapBitsSetTypeNoScan and hasPointers,
since they no longer need different cases for 1, 2, and 3+ word
objects. They can instead just manipulate the heap bitmap for the
first word and be done with it.
In order to enable this, we change heapBitsSetType and runGCProg to
always set the scan/dead bit to scan for the first word on every code
path. Since these functions only apply to types that have pointers,
there's no need to do this conditionally: it's *always* necessary to
set the scan bit in the first word.
We also change every place that scans an object and checks if there
are more pointers. Rather than only checking morePointers if the word
is >= 2, we now check morePointers if word != 1 (since that's the
checkmark word).
Looking forward, we should probably reclaim the checkmark bit, too,
but that's going to be quite a bit more work.
Tested by setting doubleCheck in heapBitsSetType and running all.bash
on both linux/amd64 and linux/386, and by running GOGC=10 all.bash.
This particularly improves the FmtFprintf* go1 benchmarks, since they
do a large amount of noscan allocation.
name old time/op new time/op delta
BinaryTree17-12 2.34s ± 1% 2.38s ± 1% +1.70% (p=0.000 n=17+19)
Fannkuch11-12 2.09s ± 0% 2.09s ± 1% ~ (p=0.276 n=17+16)
FmtFprintfEmpty-12 44.9ns ± 2% 44.8ns ± 2% ~ (p=0.340 n=19+18)
FmtFprintfString-12 127ns ± 0% 125ns ± 0% -1.57% (p=0.000 n=16+15)
FmtFprintfInt-12 128ns ± 0% 122ns ± 1% -4.45% (p=0.000 n=15+20)
FmtFprintfIntInt-12 207ns ± 1% 193ns ± 0% -6.55% (p=0.000 n=19+14)
FmtFprintfPrefixedInt-12 197ns ± 1% 191ns ± 0% -2.93% (p=0.000 n=17+18)
FmtFprintfFloat-12 263ns ± 0% 248ns ± 1% -5.88% (p=0.000 n=15+19)
FmtManyArgs-12 794ns ± 0% 779ns ± 1% -1.90% (p=0.000 n=18+18)
GobDecode-12 7.14ms ± 2% 7.11ms ± 1% ~ (p=0.072 n=20+20)
GobEncode-12 5.85ms ± 1% 5.82ms ± 1% -0.49% (p=0.000 n=20+20)
Gzip-12 218ms ± 1% 215ms ± 1% -1.22% (p=0.000 n=19+19)
Gunzip-12 36.8ms ± 0% 36.7ms ± 0% -0.18% (p=0.006 n=18+20)
HTTPClientServer-12 77.1µs ± 4% 77.1µs ± 3% ~ (p=0.945 n=19+20)
JSONEncode-12 15.6ms ± 1% 15.9ms ± 1% +1.68% (p=0.000 n=18+20)
JSONDecode-12 55.2ms ± 1% 53.6ms ± 1% -2.93% (p=0.000 n=17+19)
Mandelbrot200-12 4.05ms ± 1% 4.05ms ± 0% ~ (p=0.306 n=17+17)
GoParse-12 3.14ms ± 1% 3.10ms ± 1% -1.31% (p=0.000 n=19+18)
RegexpMatchEasy0_32-12 69.3ns ± 1% 70.0ns ± 0% +0.89% (p=0.000 n=19+17)
RegexpMatchEasy0_1K-12 237ns ± 1% 236ns ± 0% -0.62% (p=0.000 n=19+16)
RegexpMatchEasy1_32-12 69.5ns ± 1% 70.3ns ± 1% +1.14% (p=0.000 n=18+17)
RegexpMatchEasy1_1K-12 377ns ± 1% 366ns ± 1% -3.03% (p=0.000 n=15+19)
RegexpMatchMedium_32-12 107ns ± 1% 107ns ± 2% ~ (p=0.318 n=20+19)
RegexpMatchMedium_1K-12 33.8µs ± 3% 33.5µs ± 1% -1.04% (p=0.001 n=20+19)
RegexpMatchHard_32-12 1.68µs ± 1% 1.73µs ± 0% +2.50% (p=0.000 n=20+18)
RegexpMatchHard_1K-12 50.8µs ± 1% 52.0µs ± 1% +2.50% (p=0.000 n=19+18)
Revcomp-12 381ms ± 1% 385ms ± 1% +1.00% (p=0.000 n=17+18)
Template-12 64.9ms ± 3% 62.6ms ± 1% -3.55% (p=0.000 n=19+18)
TimeParse-12 324ns ± 0% 328ns ± 1% +1.25% (p=0.000 n=18+18)
TimeFormat-12 345ns ± 0% 334ns ± 0% -3.31% (p=0.000 n=15+17)
[Geo mean] 52.1µs 51.5µs -1.00%
Change-Id: I13e74da3193a7f80794c654f944d1f0d60817049
Reviewed-on: https://go-review.googlesource.com/22632
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
heapBits.bits is carefully written to produce good machine code. Use
it in heapBits.morePointers and heapBits.isPointer to get good machine
code there, too.
Change-Id: I208c7d0d38697e7a22cad67f692162589b75f1e2
Reviewed-on: https://go-review.googlesource.com/22630
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This converts all remaining uses of mspan.start to instead use
mspan.base(). In many cases, this actually reduces the complexity of
the code.
Change-Id: If113840e00d3345a6cf979637f6a152e6344aee7
Reviewed-on: https://go-review.googlesource.com/22590
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Our compilers now provides instrinsics including
sys.Ctz64 that support CTZ (count trailing zero)
instructions. This CL replaces the Go versions
of CTZ with the compiler intrinsic.
Count trailing zeros CTZ finds the least
significant 1 in a word and returns the number
of less significant 0s in the word.
Allocation uses the bitmap created by the garbage
collector to locate an unmarked object. The logic
takes a word of the bitmap, complements, and then
caches it. It then uses CTZ to locate an available
unmarked object. It then shifts marked bits out of
the bitmap word preparing it for the next search.
Once all the unmarked objects are used in the
cached work the bitmap gets another word and
repeats the process.
Change-Id: Id2fc42d1d4b9893efaa2e1bd01896985b7e42f82
Reviewed-on: https://go-review.googlesource.com/21366
Reviewed-by: Austin Clements <austin@google.com>
Two changes are included here that are dependent on the other.
The first is that allocBits and gcamrkBits are changed to
a *uint8 which points to the first byte of that span's
mark and alloc bits. Several places were altered to
perform pointer arithmetic to locate the byte corresponding
to an object in the span. The actual bit corresponding
to an object is indexed in the byte by using the lower three
bits of the objects index.
The second change avoids the redundant calculation of an
object's index. The index is returned from heapBitsForObject
and then used by the functions indexing allocBits
and gcmarkBits.
Finally we no longer allocate the gc bits in the span
structures. Instead we use an arena based allocation scheme
that allows for a more compact bit map as well as recycling
and bulk clearing of the mark bits.
Change-Id: If4d04b2021c092ec39a4caef5937a8182c64dfef
Reviewed-on: https://go-review.googlesource.com/20705
Reviewed-by: Austin Clements <austin@google.com>
Prior to this CL the base of a span was calculated in various
places using shifts or calls to base(). This CL now
always calls base() which has been optimized to calculate the
base of the span when the span is initialized and store that
value in the span structure.
Change-Id: I661f2bfa21e3748a249cdf049ef9062db6e78100
Reviewed-on: https://go-review.googlesource.com/20703
Reviewed-by: Austin Clements <austin@google.com>
Prior to this CL the sweep phase was responsible for locating
all objects that were about to be freed and calling a function
to process the object. This was done by the function
heapBitsSweepSpan. Part of processing included calls to
tracefree and msanfree as well as counting how many objects
were freed.
The calls to tracefree and msanfree have been moved into the
gcmalloc routine and called when the object is about to be
reallocated. The counting of free objects has been optimized
using an array based popcnt algorithm and if all the objects
in a span are free then span is freed.
Similarly the code to locate the next free object has been
optimized to use an array based ctz (count trailing zero).
Various hot paths in the allocation logic have been optimized.
At this point the garbage benchmark is within 3% of the 1.6
release.
Change-Id: I00643c442e2ada1685c010c3447e4ea8537d2dfa
Reviewed-on: https://go-review.googlesource.com/20201
Reviewed-by: Austin Clements <austin@google.com>
Add to each span a 64 bit cache (allocCache) of the allocBits
at freeindex. allocCache is shifted such that the lowest bit
corresponds to the bit freeindex. allocBits uses a 0 to
indicate an object is free, on the other hand allocCache
uses a 1 to indicate an object is free. This facilitates
ctz64 (count trailing zero) which counts the number of 0s
trailing the least significant 1. This is also the index of
the least significant 1.
Each span maintains a freeindex indicating the boundary
between allocated objects and unallocated objects. allocCache
is shifted as freeindex is incremented such that the low bit
in allocCache corresponds to the bit a freeindex in the
allocBits array.
Currently ctz64 is written in Go using a for loop so it is
not very efficient. Use of the hardware instruction will
follow. With this in mind comparisons of the garbage
benchmark are as follows.
1.6 release 2.8 seconds
dev:garbage branch 3.1 seconds.
Profiling shows the go implementation of ctz64 takes up
1% of the total time.
Change-Id: If084ed9c3b1eda9f3c6ab2e794625cb870b8167f
Reviewed-on: https://go-review.googlesource.com/20200
Reviewed-by: Austin Clements <austin@google.com>
Most (all?) processors that Go supports supply a hardware
instruction that takes a byte and returns the number
of zeros trailing the first 1 encountered, or 8
if no ones are found. This is the index within the
byte of the first 1 encountered. CTZ should improve the
performance of the nextFreeIndex function.
Since nextFreeIndex wants the next unmarked (0) bit
a bit-wise complement is needed before calling ctz.
Furthermore unmarked bits associated with previously
allocated objects need to be ignored. Instead of writing
a 1 as we allocate the code masks all bits less than the
freeindex after loading the byte.
While this CL does not actual execute a CTZ instruction
it supplies a ctz function with the appropiate signature
along with the logic to execute it.
Change-Id: I5c55ce0ed48ca22c21c4dd9f969b0819b4eadaa7
Reviewed-on: https://go-review.googlesource.com/20169
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Instead of building a freelist from the mark bits generated
by the GC this CL allocates directly from the mark bits.
The approach moves the mark bits from the pointer/no pointer
heap structures into their own per span data structures. The
mark/allocation vectors consist of a single mark bit per
object. Two vectors are maintained, one for allocation and
one for the GC's mark phase. During the GC cycle's sweep
phase the interpretation of the vectors is swapped. The
mark vector becomes the allocation vector and the old
allocation vector is cleared and becomes the mark vector that
the next GC cycle will use.
Marked entries in the allocation vector indicate that the
object is not free. Each allocation vector maintains a boundary
between areas of the span already allocated from and areas
not yet allocated from. As objects are allocated this boundary
is moved until it reaches the end of the span. At this point
further allocations will be done from another span.
Since we no longer sweep a span inspecting each freed object
the responsibility for maintaining pointer/scalar bits in
the heapBitMap containing is now the responsibility of the
the routines doing the actual allocation.
This CL is functionally complete and ready for performance
tuning.
Change-Id: I336e0fc21eef1066e0b68c7067cc71b9f3d50e04
Reviewed-on: https://go-review.googlesource.com/19470
Reviewed-by: Austin Clements <austin@google.com>
The gcmarkBits is a bit vector used by the GC to mark
reachable objects. Once a GC cycle is complete the gcmarkBits
swap places with the allocBits. allocBits is then used directly
by malloc to locate free objects, thus avoiding the
construction of a linked free list. This CL introduces a set
of helper functions for manipulating gcmarkBits and allocBits
that will be used by later CLs to realize the actual
algorithm. Minimal attempts have been made to optimize these
helper routines.
Change-Id: I55ad6240ca32cd456e8ed4973c6970b3b882dd34
Reviewed-on: https://go-review.googlesource.com/19420
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Rick Hudson <rlh@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
These are used at the bottom level of various GC operations that must
not be preempted. To be on the safe side, mark them all nosplit.
Change-Id: I8f7360e79c9852bd044df71413b8581ad764380c
Reviewed-on: https://go-review.googlesource.com/22504
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Rick Hudson <rlh@golang.org>
This is a subset of https://golang.org/cl/20022 with only the copyright
header lines, so the next CL will be smaller and more reviewable.
Go policy has been single space after periods in comments for some time.
The copyright header template at:
https://golang.org/doc/contribute.html#copyright
also uses a single space.
Make them all consistent.
Change-Id: Icc26c6b8495c3820da6b171ca96a74701b4a01b0
Reviewed-on: https://go-review.googlesource.com/20111
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Currently the heapBitsSweepSpan comment claims that heapBitsSweepSpan
sets the heap bitmap for the first two words to dead. In fact, it sets
the first *four* words to scalar/dead. This is important because first
two words don't actually have a dead bit, so for objects larger than
two words it *must* set a dead bit in third word to reset the object
to a "noscan" state. For example, we use this in heapBits.hasPointers
to detect that an object larger than two words is noscan.
Change-Id: Ie166a628bed5060851db083475c7377adb349d6c
Reviewed-on: https://go-review.googlesource.com/19630
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This comment is probably a hold-over from when the heap bitmap was
interleaved and the shift was 0, 2, 4, or 6. Now the shift is 0, 1, 2,
or 3.
Change-Id: I096ec729e1ca31b708455c98b573dd961d16aaee
Reviewed-on: https://go-review.googlesource.com/18531
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Rick Hudson <rlh@golang.org>
If you set GODEBUG=cgocheck=2 the runtime package will use the write
barrier to detect cases where a Go program writes a Go pointer into
non-Go memory. In conjunction with the existing cgo checks, and the
not-yet-implemented cgo check for exported functions, this should
reliably detect all cases (that do not import the unsafe package) in
which a Go pointer is incorrectly shared with C code. This check is
optional because it turns on the write barrier at all times, which is
known to be expensive.
Update #12416.
Change-Id: I549d8b2956daa76eac853928e9280e615d6365f4
Reviewed-on: https://go-review.googlesource.com/16899
Reviewed-by: Russ Cox <rsc@golang.org>
runtime/internal/sys will hold system-, architecture- and config-
specific constants.
Updates #11647
Change-Id: I6db29c312556087a42e8d2bdd9af40d157c56b54
Reviewed-on: https://go-review.googlesource.com/16817
Reviewed-by: Russ Cox <rsc@golang.org>
Applies to types fixAlloc, mCache, mCentral, mHeap, mSpan, and
mSpanList.
Two special cases:
1. mHeap_Scavenge() previously didn't take an *mheap parameter, so it
was specially handled in this CL.
2. mHeap_Free() would have collided with mheap's "free" field, so it's
been renamed to (*mheap).freeSpan to parallel its underlying
(*mheap).freeSpanLocked method.
Change-Id: I325938554cca432c166fe9d9d689af2bbd68de4b
Reviewed-on: https://go-review.googlesource.com/16221
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This change breaks out most of the atomics functions in the runtime
into package runtime/internal/atomic. It adds some basic support
in the toolchain for runtime packages, and also modifies linux/arm
atomics to remove the dependency on the runtime's mutex. The mutexes
have been replaced with spinlocks.
all trybots are happy!
In addition to the trybots, I've tested on the darwin/arm64 builder,
on the darwin/arm builder, and on a ppc64le machine.
Change-Id: I6698c8e3cf3834f55ce5824059f44d00dc8e3c2f
Reviewed-on: https://go-review.googlesource.com/14204
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Change compiler-invoked interface functions to directly take
iface/eface parameters instead of fInterface/interface{} to avoid
needing to always convert.
For the handful of functions that legitimately need to take an
interface{} parameter, add efaceOf to type-safely convert *interface{}
to *eface.
Change-Id: I8928761a12fd3c771394f36adf93d3006a9fcf39
Reviewed-on: https://go-review.googlesource.com/16166
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
By default, the runtime panics if it detects a pointer to an
unallocated span. At this point, this usually catches bad uses of
unsafe or cgo in user code (though it could also catch runtime bugs).
Unfortunately, the rather cryptic error misleads users, offers users
little help with debugging their own problem, and offers the Go
developers little help with root-causing.
Improve the error message in various ways. First, the wording is
improved to make it clearer what condition was detected and to suggest
that this may be the result of incorrect use of unsafe or cgo. Second,
we add a dump of the object containing the bad pointer so that there's
at least some hope of figuring out why a bad pointer was stored in the
Go heap.
Change-Id: I57b91b12bc3cb04476399d7706679e096ce594b9
Reviewed-on: https://go-review.googlesource.com/14763
Reviewed-by: Rick Hudson <rlh@golang.org>
Changes the torture test in #12068 from failing about 1/10 times
to not failing in almost 2,000 runs.
This was only happening in -race mode because functions are
bigger in -race mode, so a few of the helpers for heapBitsBulkBarrier
were not being inlined, and they were not marked nosplit,
so (only in -race mode) the write barrier was being preempted by GC,
causing missed pointer updates.
Filed issue #12069 for diagnosis of any other similar errors.
Fixes#12068.
Change-Id: Ic174d9b050ba278b18b08ab0d85a73c33bd5b175
Reviewed-on: https://go-review.googlesource.com/13364
Reviewed-by: Austin Clements <austin@google.com>
Also make invalidptr control the recently added GC pointer check,
as documented.
Change-Id: Iccfdf49480219d12be8b33b8f03d8312d8ceabed
Reviewed-on: https://go-review.googlesource.com/12857
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
The last time we tried this, linux/arm64 broke.
The series of CLs leading to this one fixes that problem.
Let's try again.
Fixes#9880.
Change-Id: I67bc1d959175ec972d4dcbe4aa6f153790f74251
Reviewed-on: https://go-review.googlesource.com/12849
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
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>
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>
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>
Austin Clements
Nick Craig-Wood
Gleb Stepanov
Elias Naur
Rick Hudson
David Crawshaw
Brad Fitzpatrick
Ian Lance Taylor
Michael Matloob
Matthew Dempsky
Russ Cox