Russ Cox [Wed, 27 Aug 2014 15:32:17 +0000 (11:32 -0400)]
cmd/cc, runtime: convert C compilers to use Go calling convention
To date, the C compilers and Go compilers differed only in how
values were returned from functions. This made it difficult to call
Go from C or C from Go if return values were involved. It also made
assembly called from Go and assembly called from C different.
This CL changes the C compiler to use the Go conventions, passing
results on the stack, after the arguments.
[Exception: this does not apply to C ... functions, because you can't
know where on the stack the arguments end.]
By doing this, the CL makes it possible to rewrite C functions into Go
one at a time, without worrying about which languages call that
function or which languages it calls.
This CL also updates all the assembly files in package runtime to use
the new conventions. Argument references of the form 40(SP) have
been rewritten to the form name+10(FP) instead, and there are now
Go func prototypes for every assembly function called from C or Go.
This means that 'go vet runtime' checks effectively every assembly
function, and go vet's output was used to automate the bulk of the
conversion.
Some functions, like seek and nsec on Plan 9, needed to be rewritten.
Many assembly routines called from C were reading arguments
incorrectly, using MOVL instead of MOVQ or vice versa, especially on
the less used systems like openbsd.
These were found by go vet and have been corrected too.
If we're lucky, this may reduce flakiness on those systems.
Tested on:
darwin/386
darwin/amd64
linux/arm
linux/386
linux/amd64
If this breaks another system, the bug is almost certainly in the
sys_$GOOS_$GOARCH.s file, since the rest of the CL is tested
by the combination of the above systems.
Rick Hudson [Wed, 27 Aug 2014 15:15:47 +0000 (11:15 -0400)]
runtime: changes to g->atomicstatus (nee status) to support concurrent GC
Every change to g->atomicstatus is now done atomically so that we can
ensure that all gs pass through a gc safepoint on demand. This allows
the GC to move from one phase to the next safely. In some phases the
stack will be scanned. This CL only deals with the infrastructure that
allows g->atomicstatus to go from one state to another. Future CLs
will deal with scanning and monitoring what phase the GC is in.
The major change was to moving to using a Gscan bit to indicate that
the status is in a scan state. The only bug fix was in oldstack where
I wasn't moving to a Gcopystack state in order to block scanning until
the new stack was in place. The proc.go file is waiting for an atomic
load instruction.
Dave Cheney [Wed, 27 Aug 2014 05:23:38 +0000 (15:23 +1000)]
cmd/gc: fix undefined behaviour warnings in mparith3.c
Update #8527
Fixes two warnings:
src/cmd/gc/mparith3.c:255:10: runtime error: shift exponent 52 is too large for 32-bit type 'int'
src/cmd/gc/mparith3.c:254:14: runtime error: shift exponent 52 is too large for 32-bit type 'int'
Rob Pike [Tue, 26 Aug 2014 21:45:53 +0000 (14:45 -0700)]
time: use go generate rather than Makefile (windows only)
Also make genzabbrs.go more self-contained.
Also run it (on Linux; does that matter?) to update the table.
Dave Cheney [Tue, 26 Aug 2014 05:39:04 +0000 (05:39 +0000)]
runtime: convert int64tofloat64, uint64tofloat64 to Go
I noticed that 5g doesn't flush the float64 result back to the stack, hence the change in the function signature. I'm wondering if I should also change the signature for the other two functions.
Brad Fitzpatrick [Tue, 26 Aug 2014 04:38:39 +0000 (21:38 -0700)]
io: document that Readers and Writers must not retain buffers
There are both many callers and many implementations of these
interfaces, so make the contract explicit. Callers generally
assume this, and at least the standard library and other
implementations obey this, but it's never stated explicitly,
making it somewhat risky to assume.
Rob Pike [Mon, 25 Aug 2014 21:56:35 +0000 (14:56 -0700)]
unicode/maketables: add -output flag, buffer output, use gofmt
Simplify the invocation (and speed it up substantially) in preparation
for move to go generate.
Dmitriy Vyukov [Mon, 25 Aug 2014 19:30:39 +0000 (23:30 +0400)]
runtime: restore scavenger constants
Once and for all.
Broken in cl/108640043.
I've messed it before. To test scavenger-related changes
one needs to alter the constants during final testing.
And then it's very easy to submit with the altered constants.
Russ Cox [Mon, 25 Aug 2014 18:38:19 +0000 (14:38 -0400)]
cmd/gc, runtime: treat slices and strings like pointers in garbage collection
Before, a slice with cap=0 or a string with len=0 might have its
base pointer pointing beyond the actual slice/string data into
the next block. The collector had to ignore slices and strings with
cap=0 in order to avoid misinterpreting the base pointer.
Now, a slice with cap=0 or a string with len=0 still has a base
pointer pointing into the actual slice/string data, no matter what.
The collector can now always scan the pointer, which means
strings and slices are no longer special.
Dmitriy Vyukov [Mon, 25 Aug 2014 16:59:52 +0000 (20:59 +0400)]
runtime: remove dedicated scavenger thread
A whole thread is too much for background scavenger that sleeps all the time anyway.
We already have sysmon thread that can do this work.
Also remove g->isbackground and simplify enter/exitsyscall.
Russ Cox [Mon, 25 Aug 2014 11:05:45 +0000 (07:05 -0400)]
cmd/gc: fix order of channel evaluation of receive channels
Normally, an expression of the form x.f or *y can be reordered
with function calls and communications.
Select is stricter than normal: each channel expression is evaluated
in source order. If you have case <-x.f and case <-foo(), then if the
evaluation of x.f causes a panic, foo must not have been called.
(This is in contrast to an expression like x.f + foo().)
Enforce this stricter ordering.
Fixes #8336.
LGTM=dvyukov
R=golang-codereviews, dvyukov
CC=golang-codereviews, r
https://golang.org/cl/126570043
cmd/5g, cmd/6g, cmd/8g: clear Addr node when registerizing
Update #8525
Some temporary variables that were fully registerized nevertheless had stack space allocated for them because the Addrs were still marked as having associated nodes.
Distribution of stack space reserved for temporary variables while running make.bash (6g):
BEFORE
40.89% 7026 allocauto: 0 to 0
7.83% 1346 allocauto: 0 to 24
7.22% 1241 allocauto: 0 to 8
6.30% 1082 allocauto: 0 to 16
4.96% 853 allocauto: 0 to 56
4.59% 789 allocauto: 0 to 32
2.97% 510 allocauto: 0 to 40
2.32% 399 allocauto: 0 to 48
2.10% 360 allocauto: 0 to 64
1.91% 328 allocauto: 0 to 72
AFTER
48.49% 8332 allocauto: 0 to 0
9.52% 1635 allocauto: 0 to 16
5.28% 908 allocauto: 0 to 48
4.80% 824 allocauto: 0 to 32
4.73% 812 allocauto: 0 to 8
3.38% 581 allocauto: 0 to 24
2.35% 404 allocauto: 0 to 40
2.32% 399 allocauto: 0 to 64
1.65% 284 allocauto: 0 to 56
1.34% 230 allocauto: 0 to 72
Russ Cox [Mon, 25 Aug 2014 00:28:29 +0000 (20:28 -0400)]
runtime: remove some overuse of uintptr/unsafe.Pointer
Now 'go vet runtime' only shows:
malloc.go:200: possible misuse of unsafe.Pointer
malloc.go:214: possible misuse of unsafe.Pointer
malloc.go:250: possible misuse of unsafe.Pointer
stubs.go:167: possible misuse of unsafe.Pointer
I think that when we moved all stacks into heap,
we introduced a bunch of bad data races. This was later
worsened by parallel stack shrinking.
Observation 1: exitsyscall can allocate a stack from heap at any time (including during STW).
Observation 2: parallel stack shrinking can (surprisingly) grow heap during marking.
Consider that we steadily grow stacks of a number of goroutines from 8K to 16K.
And during GC they all can be shrunk back to 8K. Shrinking will allocate lots of 8K
stacks, and we do not necessary have that many in heap at this moment. So shrinking
can grow heap as well.
Consequence: any access to mheap.allspans in GC (and otherwise) must take heap lock.
This is not true in several places.
Fix this by protecting accesses to mheap.allspans and introducing allspans cache for marking,
similar to what we use for sweeping.
Dmitriy Vyukov [Sun, 24 Aug 2014 08:04:51 +0000 (12:04 +0400)]
runtime: cache unrolled GC bitmask
Cache unrolled GC bitmask for types up to 64/32K on 64/32-bit systems,
this corresponds to up to 4K cached bitmask.
Perf builders say that 2% of time is spent in unrollgcproginplace_m/unrollgcprog1
on http benchmark:
http://goperfd.appspot.com/log/f42045f45bf61a0da53b724a7c8567824a0ad6c9
Russ Cox [Sun, 24 Aug 2014 03:01:59 +0000 (23:01 -0400)]
runtime: adjust errorCString definition to avoid allocation
The low-level implementation of divide on ARM assumes that
it can panic with an error created by newErrorCString without
allocating. If we make interface data words require pointer values,
the current definition would require an allocation when stored
in an interface. Changing the definition to use unsafe.Pointer
instead of uintptr avoids the allocation. This change is okay
because the field really is a pointer (to a C string in rodata).
««« original CL description
cmd/gc: change interface representation: only pointers in data word
Note that there are various cleanups that can be made if we keep
this change, but I do not want to start making changes that
depend on this one until the 1.4 cycle closes.
Russ Cox [Sat, 23 Aug 2014 23:24:44 +0000 (19:24 -0400)]
cmd/gc: change interface representation: only pointers in data word
Note that there are various cleanups that can be made if we keep
this change, but I do not want to start making changes that
depend on this one until the 1.4 cycle closes.
Dmitriy Vyukov [Fri, 22 Aug 2014 17:27:25 +0000 (21:27 +0400)]
runtime: please vet
The current code is correct, but vet does not understand it:
asm_amd64.s:963: [amd64] invalid MOVL of ret+0(FP); int64 is 8-byte value
asm_amd64.s:964: [amd64] invalid offset ret+4(FP); expected ret+0(FP)
Alberto Donizetti [Thu, 21 Aug 2014 17:35:43 +0000 (10:35 -0700)]
time: removed from tests now obsolete assumption about Australian tz abbreviations
Australian timezones abbreviation for standard and daylight saving time were recently
changed from EST for both to AEST and AEDT in the icann tz database (see changelog
on www.iana.org/time-zones).
A test in the time package was written to check that the ParseInLocation function
understand that Feb EST and Aug EST are different time zones, even though they are
both called EST. This is no longer the case, and the Date function now returns
AEST or AEDT for australian tz on every Linux system with an up to date tz database
(and this makes the test fail).
Since I wasn't able to find another country that 1) uses daylight saving and 2) has
the same abbreviation for both on tzdata, I changed the test to make sure that
ParseInLocation does not get confused when it parses, in different locations, two
dates with the same abbreviation (this was suggested in the mailing list).
Dmitriy Vyukov [Thu, 21 Aug 2014 17:10:30 +0000 (21:10 +0400)]
runtime: remove now arg from timer callback
Cleanup before converting to Go.
Fortunately nobody using it, because it is incorrect:
monotonic runtime time instead of claimed real time.
Dmitriy Vyukov [Thu, 21 Aug 2014 08:34:26 +0000 (12:34 +0400)]
cmd/gc: fix undefined behavior
UndefinedBehaviorSanitizer claims it is UB in C:
src/cmd/gc/racewalk.c:422:37: runtime error: member access within null pointer of type 'Node' (aka 'struct Node')
src/cmd/gc/racewalk.c:423:37: runtime error: member access within null pointer of type 'Node' (aka 'struct Node')
Dmitriy Vyukov [Thu, 21 Aug 2014 07:46:53 +0000 (11:46 +0400)]
runtime: fix deadlock when gctrace
Calling ReadMemStats which does stoptheworld on m0 holding locks
was not a good idea.
Stoptheworld holding locks is a recipe for deadlocks (added check for this).
Stoptheworld on g0 may or may not work (added check for this as well).
As far as I understand scavenger will print incorrect numbers now,
as stack usage is not subtracted from heap. But it's better than deadlocking.
Brad Fitzpatrick [Wed, 20 Aug 2014 01:45:05 +0000 (18:45 -0700)]
net/http: fix TimeoutHandler data races; hold lock longer
The existing lock needed to be held longer. If a timeout occured
while writing (but after the guarded timeout check), the writes
would clobber a future connection's buffer.
Also remove a harmless warning by making Write also set the
flag that headers were sent (implicitly), so we don't try to
write headers later (a no-op + warning) on timeout after we've
started writing.