tlinux pre-2.6 implementation - plan9port - [fork] Plan 9 from user space
(HTM) git clone git://src.adamsgaard.dk/plan9port
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---
(DIR) commit f1e8706de85f43523a789f4411b5727ed5211ec3
(DIR) parent 4dbefdd41ca866a10cee633a3ee9a67d9204b052
(HTM) Author: rsc <devnull@localhost>
Date: Mon, 27 Dec 2004 16:52:46 +0000
linux pre-2.6 implementation
Diffstat:
A src/libthread/Linux.c | 348 +++++++++++++++++++++++++++++++
A src/libthread/Linuxasm.s | 7 +++++++
2 files changed, 355 insertions(+), 0 deletions(-)
---
(DIR) diff --git a/src/libthread/Linux.c b/src/libthread/Linux.c
t@@ -0,0 +1,348 @@
+#include "u.h"
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sched.h>
+#include <signal.h>
+#include "libc.h"
+#include "thread.h"
+#include "threadimpl.h"
+
+/*
+ * spin locks
+ */
+extern int _tas(int*);
+
+void
+_threadunlock(Lock *l, ulong pc)
+{
+ USED(pc);
+
+ l->held = 0;
+}
+
+int
+_threadlock(Lock *l, int block, ulong pc)
+{
+ int i;
+
+ USED(pc);
+
+ /* once fast */
+ if(!_tas(&l->held))
+ return 1;
+ if(!block)
+ return 0;
+
+ /* a thousand times pretty fast */
+ for(i=0; i<1000; i++){
+ if(!_tas(&l->held))
+ return 1;
+ sched_yield();
+ }
+ /* now nice and slow */
+ for(i=0; i<1000; i++){
+ if(!_tas(&l->held))
+ return 1;
+ usleep(100*1000);
+ }
+ /* take your time */
+ while(_tas(&l->held))
+ usleep(1000*1000);
+ return 1;
+}
+
+/*
+ * sleep and wakeup
+ */
+static void
+ign(int x)
+{
+ USED(x);
+}
+
+static void /*__attribute__((constructor))*/
+ignusr1(int restart)
+{
+ struct sigaction sa;
+
+ memset(&sa, 0, sizeof sa);
+ sa.sa_handler = ign;
+ sigemptyset(&sa.sa_mask);
+ sigaddset(&sa.sa_mask, SIGUSR1);
+ if(restart)
+ sa.sa_flags = SA_RESTART;
+ sigaction(SIGUSR1, &sa, nil);
+}
+
+void
+_procsleep(_Procrendez *r)
+{
+ sigset_t mask;
+
+ /*
+ * Go to sleep.
+ *
+ * Block USR1, set the handler to interrupt system calls,
+ * unlock the vouslock so our waker can wake us,
+ * and then suspend.
+ */
+ r->asleep = 1;
+ r->pid = getpid();
+
+ sigprocmask(SIG_SETMASK, nil, &mask);
+ sigaddset(&mask, SIGUSR1);
+ sigprocmask(SIG_SETMASK, &mask, nil);
+ ignusr1(0);
+ unlock(r->l);
+ sigdelset(&mask, SIGUSR1);
+ sigsuspend(&mask);
+
+ /*
+ * We're awake. Make USR1 not interrupt system calls.
+ */
+ ignusr1(1);
+ assert(r->asleep == 0);
+ lock(r->l);
+}
+
+void
+_procwakeup(_Procrendez *r)
+{
+ if(r->asleep){
+ r->asleep = 0;
+ assert(r->pid >= 1);
+ kill(r->pid, SIGUSR1);
+ }
+}
+
+/*
+ * process creation and exit
+ */
+typedef struct Stackfree Stackfree;
+struct Stackfree
+{
+ Stackfree *next;
+ int pid;
+};
+static Lock stacklock;
+static Stackfree *stackfree;
+
+static void
+delayfreestack(uchar *stk)
+{
+ Stackfree *sf;
+
+ sf = (Stackfree*)stk;
+ sf->pid = getpid();
+ lock(&stacklock);
+ sf->next = stackfree;
+ stackfree = sf;
+ unlock(&stacklock);
+}
+
+static void
+dofreestacks(void)
+{
+ Stackfree *sf, *last, *next;
+
+ if(stackfree==nil || !canlock(&stacklock))
+ return;
+
+ for(last=nil,sf=stackfree; sf; last=sf,sf=next){
+ next = sf->next;
+ if(sf->pid >= 1 && kill(sf->pid, 0) < 0 && errno == ESRCH){
+ free(sf);
+ last->next = next;
+ sf = last;
+ }
+ }
+}
+
+static int
+startprocfn(void *v)
+{
+ void **a;
+ uchar *stk;
+ void (*fn)(void*);
+ Proc *p;
+
+ a = (void**)v;
+ fn = a[0];
+ p = a[1];
+ stk = a[2];
+ free(a);
+ p->osprocid = getpid();
+
+ (*fn)(p);
+
+ delayfreestack(stk);
+ _exit(0);
+ return 0;
+}
+
+/*
+ * indirect through here so that parent need not wait for child zombie
+ *
+ * slight race - if child exits and then another process starts before we
+ * manage to exit, we'll be running on a freed stack.
+ */
+static int
+trampnowait(void *v)
+{
+ void **a;
+
+ a = (void*)v;
+ *(int*)a[3] = clone(startprocfn, a[2]+65536-512, CLONE_VM|CLONE_FILES, a);
+ _exit(0);
+ return 0;
+}
+
+void
+_procstart(Proc *p, void (*fn)(Proc*))
+{
+ void **a;
+ uchar *stk;
+ int pid, kidpid, status;
+
+ dofreestacks();
+ a = malloc(4*sizeof a[0]);
+ if(a == nil)
+ sysfatal("_procstart malloc: %r");
+ stk = malloc(65536);
+ if(stk == nil)
+ sysfatal("_procstart malloc stack: %r");
+
+ a[0] = fn;
+ a[1] = p;
+ a[2] = stk;
+ a[3] = &kidpid;
+ kidpid = -1;
+
+ pid = clone(trampnowait, stk+65536-16, CLONE_VM|CLONE_FILES, a);
+ if(pid > 0)
+ if(wait4(pid, &status, __WALL, 0) < 0)
+ fprint(2, "ffork wait4: %r\n");
+ if(pid < 0 || kidpid < 0){
+ fprint(2, "_procstart clone: %r\n");
+ abort();
+ }
+}
+
+static char *threadexitsmsg;
+void
+sigusr2handler(int s)
+{
+ if(threadexitsmsg)
+ _exits(threadexitsmsg);
+}
+
+void
+threadexitsall(char *msg)
+{
+ static int pid[1024];
+ int i, npid, mypid;
+ Proc *p;
+
+ if(msg == nil)
+ msg = "";
+ mypid = getpid();
+ lock(&_threadprocslock);
+ threadexitsmsg = msg;
+ npid = 0;
+ for(p=_threadprocs; p; p=p->next)
+ if(p->osprocid != mypid && p->osprocid >= 1)
+ pid[npid++] = p->osprocid;
+ for(i=0; i<npid; i++)
+ kill(pid[i], SIGUSR2);
+ unlock(&_threadprocslock);
+ exits(msg);
+}
+
+/*
+ * per-process data, indexed by pid
+ *
+ * could use modify_ldt and a segment register
+ * to avoid the many calls to getpid(), but i don't
+ * care -- this is compatibility code. linux 2.6 with
+ * nptl is a good enough pthreads to avoid this whole file.
+ */
+typedef struct Perproc Perproc;
+struct Perproc
+{
+ int pid;
+ Proc *proc;
+};
+
+static Lock perlock;
+static Perproc perproc[1024];
+#define P ((Proc*)-1)
+
+static Perproc*
+myperproc(void)
+{
+ int i, pid, h;
+ Perproc *p;
+
+ pid = getpid();
+ h = pid%nelem(perproc);
+ for(i=0; i<nelem(perproc); i++){
+ p = &perproc[(i+h)%nelem(perproc)];
+ if(p->pid == pid)
+ return p;
+ if(p->pid == 0){
+ print("found 0 at %d (h=%d)\n", (i+h)%nelem(perproc), h);
+ break;
+ }
+ }
+ fprint(2, "myperproc %d: cannot find self\n", pid);
+ abort();
+ return nil;
+}
+
+static Perproc*
+newperproc(void)
+{
+ int i, pid, h;
+ Perproc *p;
+
+ lock(&perlock);
+ pid = getpid();
+ h = pid%nelem(perproc);
+ for(i=0; i<nelem(perproc); i++){
+ p = &perproc[(i+h)%nelem(perproc)];
+ if(p->pid == pid || p->pid == -1 || p->pid == 0){
+ p->pid = pid;
+ unlock(&perlock);
+ return p;
+ }
+ }
+ fprint(2, "newperproc %d: out of procs\n", pid);
+ abort();
+ return nil;
+}
+
+Proc*
+_threadproc(void)
+{
+ return myperproc()->proc;
+}
+
+void
+_threadsetproc(Proc *p)
+{
+ Perproc *pp;
+
+ p->osprocid = getpid();
+ pp = newperproc();
+ pp->proc = p;
+ if(p == nil)
+ pp->pid = -1;
+}
+
+void
+_pthreadinit(void)
+{
+ signal(SIGUSR2, sigusr2handler);
+}
+
(DIR) diff --git a/src/libthread/Linuxasm.s b/src/libthread/Linuxasm.s
t@@ -0,0 +1,7 @@
+.globl _tas
+_tas:
+ movl $0xCAFEBABE, %eax
+ movl 4(%esp), %ecx
+ xchgl %eax, 0(%ecx)
+ ret
+