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0a5fae2a0e
In issue 50113, we see that a thread blocked in a system call can result
in a hang of AllThreadsSyscall. To resolve this, we must send a signal
to these threads to knock them out of the system call long enough to run
the per-thread syscall.
Stepping back, if we need to send signals anyway, it should be possible
to implement this entire mechanism on top of signals. This CL does so,
vastly simplifying the mechanism, both as a direct result of
newly-unnecessary code as well as some ancillary simplifications to make
things simpler to follow.
Major changes:
* The rest of the mechanism is moved to os_linux.go, with fields in mOS
instead of m itself.
* 'Fixup' fields and functions are renamed to 'perThreadSyscall' so they
are more precise about their purpose.
* Rather than getting passed a closure, doAllThreadsSyscall takes the
syscall number and arguments. This avoids a lot of hairy behavior:
* The closure may potentially only be live in fields in the M,
hidden from the GC. Not necessary with no closure.
* The need to loan out the race context. A direct RawSyscall6 call
does not require any race context.
* The closure previously conditionally panicked in strange
locations, like a signal handler. Now we simply throw.
* All manual fixup synchronization with mPark, sysmon, templateThread,
sigqueue, etc is gone. The core approach is much simpler:
doAllThreadsSyscall sends a signal to every thread in allm, which
executes the system call from the signal handler. We use (SIGRTMIN +
1), aka SIGSETXID, the same signal used by glibc for this purpose. As
such, we are careful to only handle this signal on non-cgo binaries.
Synchronization with thread creation is a key part of this CL. The
comment near the top of doAllThreadsSyscall describes the required
synchronization semantics and how they are achieved.
Note that current use of allocmLock protects the state mutations of allm
that are also protected by sched.lock. allocmLock is used instead of
sched.lock simply to avoid holding sched.lock for so long.
Fixes #50113
Change-Id: Ic7ea856dc66cf711731540a54996e08fc986ce84
Reviewed-on: https://go-review.googlesource.com/c/go/+/383434
Reviewed-by: Austin Clements <austin@google.com>
Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
266 lines
4.4 KiB
Go
266 lines
4.4 KiB
Go
// created by cgo -cdefs and then converted to Go
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// cgo -cdefs defs2_linux.go
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package runtime
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import "unsafe"
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const (
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_EINTR = 0x4
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_EAGAIN = 0xb
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_ENOMEM = 0xc
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_ENOSYS = 0x26
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_PROT_NONE = 0x0
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_PROT_READ = 0x1
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_PROT_WRITE = 0x2
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_PROT_EXEC = 0x4
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_MAP_ANON = 0x20
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_MAP_PRIVATE = 0x2
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_MAP_FIXED = 0x10
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_MADV_DONTNEED = 0x4
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_MADV_FREE = 0x8
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_MADV_HUGEPAGE = 0xe
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_MADV_NOHUGEPAGE = 0xf
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_SA_RESTART = 0x10000000
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_SA_ONSTACK = 0x8000000
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_SA_RESTORER = 0x4000000
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_SA_SIGINFO = 0x4
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_SI_KERNEL = 0x80
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_SI_TIMER = -0x2
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_SIGHUP = 0x1
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_SIGINT = 0x2
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_SIGQUIT = 0x3
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_SIGILL = 0x4
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_SIGTRAP = 0x5
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_SIGABRT = 0x6
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_SIGBUS = 0x7
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_SIGFPE = 0x8
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_SIGKILL = 0x9
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_SIGUSR1 = 0xa
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_SIGSEGV = 0xb
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_SIGUSR2 = 0xc
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_SIGPIPE = 0xd
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_SIGALRM = 0xe
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_SIGSTKFLT = 0x10
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_SIGCHLD = 0x11
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_SIGCONT = 0x12
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_SIGSTOP = 0x13
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_SIGTSTP = 0x14
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_SIGTTIN = 0x15
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_SIGTTOU = 0x16
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_SIGURG = 0x17
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_SIGXCPU = 0x18
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_SIGXFSZ = 0x19
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_SIGVTALRM = 0x1a
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_SIGPROF = 0x1b
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_SIGWINCH = 0x1c
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_SIGIO = 0x1d
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_SIGPWR = 0x1e
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_SIGSYS = 0x1f
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_SIGRTMIN = 0x20
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_FPE_INTDIV = 0x1
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_FPE_INTOVF = 0x2
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_FPE_FLTDIV = 0x3
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_FPE_FLTOVF = 0x4
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_FPE_FLTUND = 0x5
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_FPE_FLTRES = 0x6
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_FPE_FLTINV = 0x7
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_FPE_FLTSUB = 0x8
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_BUS_ADRALN = 0x1
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_BUS_ADRERR = 0x2
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_BUS_OBJERR = 0x3
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_SEGV_MAPERR = 0x1
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_SEGV_ACCERR = 0x2
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_ITIMER_REAL = 0x0
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_ITIMER_VIRTUAL = 0x1
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_ITIMER_PROF = 0x2
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_CLOCK_THREAD_CPUTIME_ID = 0x3
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_SIGEV_THREAD_ID = 0x4
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_O_RDONLY = 0x0
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_O_NONBLOCK = 0x800
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_O_CLOEXEC = 0x80000
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_EPOLLIN = 0x1
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_EPOLLOUT = 0x4
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_EPOLLERR = 0x8
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_EPOLLHUP = 0x10
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_EPOLLRDHUP = 0x2000
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_EPOLLET = 0x80000000
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_EPOLL_CLOEXEC = 0x80000
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_EPOLL_CTL_ADD = 0x1
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_EPOLL_CTL_DEL = 0x2
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_EPOLL_CTL_MOD = 0x3
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_AF_UNIX = 0x1
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_SOCK_DGRAM = 0x2
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)
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type fpreg struct {
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significand [4]uint16
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exponent uint16
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}
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type fpxreg struct {
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significand [4]uint16
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exponent uint16
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padding [3]uint16
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}
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type xmmreg struct {
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element [4]uint32
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}
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type fpstate struct {
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cw uint32
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sw uint32
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tag uint32
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ipoff uint32
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cssel uint32
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dataoff uint32
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datasel uint32
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_st [8]fpreg
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status uint16
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magic uint16
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_fxsr_env [6]uint32
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mxcsr uint32
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reserved uint32
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_fxsr_st [8]fpxreg
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_xmm [8]xmmreg
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padding1 [44]uint32
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anon0 [48]byte
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}
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type timespec struct {
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tv_sec int32
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tv_nsec int32
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}
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//go:nosplit
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func (ts *timespec) setNsec(ns int64) {
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ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
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}
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type timeval struct {
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tv_sec int32
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tv_usec int32
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}
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func (tv *timeval) set_usec(x int32) {
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tv.tv_usec = x
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}
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type sigactiont struct {
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sa_handler uintptr
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sa_flags uint32
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sa_restorer uintptr
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sa_mask uint64
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}
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type siginfoFields struct {
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si_signo int32
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si_errno int32
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si_code int32
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// below here is a union; si_addr is the only field we use
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si_addr uint32
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}
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type siginfo struct {
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siginfoFields
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// Pad struct to the max size in the kernel.
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_ [_si_max_size - unsafe.Sizeof(siginfoFields{})]byte
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}
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type stackt struct {
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ss_sp *byte
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ss_flags int32
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ss_size uintptr
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}
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type sigcontext struct {
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gs uint16
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__gsh uint16
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fs uint16
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__fsh uint16
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es uint16
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__esh uint16
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ds uint16
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__dsh uint16
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edi uint32
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esi uint32
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ebp uint32
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esp uint32
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ebx uint32
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edx uint32
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ecx uint32
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eax uint32
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trapno uint32
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err uint32
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eip uint32
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cs uint16
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__csh uint16
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eflags uint32
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esp_at_signal uint32
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ss uint16
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__ssh uint16
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fpstate *fpstate
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oldmask uint32
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cr2 uint32
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}
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type ucontext struct {
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uc_flags uint32
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uc_link *ucontext
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uc_stack stackt
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uc_mcontext sigcontext
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uc_sigmask uint32
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}
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type itimerspec struct {
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it_interval timespec
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it_value timespec
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}
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type itimerval struct {
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it_interval timeval
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it_value timeval
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}
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type sigeventFields struct {
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value uintptr
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signo int32
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notify int32
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// below here is a union; sigev_notify_thread_id is the only field we use
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sigev_notify_thread_id int32
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}
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type sigevent struct {
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sigeventFields
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// Pad struct to the max size in the kernel.
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_ [_sigev_max_size - unsafe.Sizeof(sigeventFields{})]byte
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}
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type epollevent struct {
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events uint32
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data [8]byte // to match amd64
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}
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type sockaddr_un struct {
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family uint16
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path [108]byte
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}
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