ref: 128ea44a89c7905612ad2fa5a61a9325ddfb5e1e
dir: /sys/src/9/port/taslock.c/
#include "u.h" #include "../port/lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "../port/error.h" #include "edf.h" long maxlockcycles; long maxilockcycles; long cumlockcycles; long cumilockcycles; uintptr maxlockpc; uintptr maxilockpc; struct { ulong locks; ulong glare; ulong inglare; } lockstats; static void dumplockmem(char *tag, Lock *l) { uchar *cp; int i; iprint("%s: ", tag); cp = (uchar*)l; for(i = 0; i < 64; i++) iprint("%2.2ux ", cp[i]); iprint("\n"); } void lockloop(Lock *l, uintptr pc) { extern int panicking; Proc *p; if(panicking) return; p = l->p; print("lock %#p loop key %#lux pc %#p held by pc %#p proc %lud\n", l, l->key, pc, l->pc, p ? p->pid : 0); dumpaproc(up); if(p != nil) dumpaproc(p); } int lock(Lock *l) { int i; uintptr pc; pc = getcallerpc(&l); lockstats.locks++; if(up) up->nlocks++; /* prevent being scheded */ if(tas(&l->key) == 0){ if(up) up->lastlock = l; l->pc = pc; l->p = up; l->m = MACHP(m->machno); l->isilock = 0; #ifdef LOCKCYCLES l->lockcycles = -lcycles(); #endif return 0; } if(up) up->nlocks--; lockstats.glare++; for(;;){ lockstats.inglare++; i = 0; while(l->key){ if(conf.nmach < 2 && up && up->edf && (up->edf->flags & Admitted)){ /* * Priority inversion, yield on a uniprocessor; on a * multiprocessor, the other processor will unlock */ print("inversion %#p pc %#p proc %lud held by pc %#p proc %lud\n", l, pc, up ? up->pid : 0, l->pc, l->p ? l->p->pid : 0); up->edf->d = todget(nil); /* yield to process with lock */ } if(i++ > 100000000){ i = 0; lockloop(l, pc); } } if(up) up->nlocks++; if(tas(&l->key) == 0){ if(up) up->lastlock = l; l->pc = pc; l->p = up; l->m = MACHP(m->machno); l->isilock = 0; #ifdef LOCKCYCLES l->lockcycles = -lcycles(); #endif return 1; } if(up) up->nlocks--; } } void ilock(Lock *l) { ulong x; uintptr pc; pc = getcallerpc(&l); lockstats.locks++; x = splhi(); if(tas(&l->key) != 0){ lockstats.glare++; /* * Cannot also check l->pc, l->m, or l->isilock here * because they might just not be set yet, or * (for pc and m) the lock might have just been unlocked. */ for(;;){ lockstats.inglare++; splx(x); while(l->key) ; x = splhi(); if(tas(&l->key) == 0) goto acquire; } } acquire: m->ilockdepth++; if(up) up->lastilock = l; l->sr = x; l->pc = pc; l->p = up; l->m = MACHP(m->machno); l->isilock = 1; #ifdef LOCKCYCLES l->lockcycles = -lcycles(); #endif } int canlock(Lock *l) { if(up) up->nlocks++; if(tas(&l->key)){ if(up) up->nlocks--; return 0; } if(up) up->lastlock = l; l->pc = getcallerpc(&l); l->p = up; l->m = MACHP(m->machno); l->isilock = 0; #ifdef LOCKCYCLES l->lockcycles = -lcycles(); #endif return 1; } void unlock(Lock *l) { #ifdef LOCKCYCLES l->lockcycles += lcycles(); cumlockcycles += l->lockcycles; if(l->lockcycles > maxlockcycles){ maxlockcycles = l->lockcycles; maxlockpc = l->pc; } #endif if(l->key == 0) print("unlock(%#p): not locked: pc %#p\n", l, getcallerpc(&l)); if(l->isilock) print("unlock(%#p) of ilock: pc %#p, held by %#p\n", l, getcallerpc(&l), l->pc); if(l->p != up){ print("unlock(%#p): up changed: pc %#p, acquired at pc %#p, lock p %#p, unlock up %#p\n", l, getcallerpc(&l), l->pc, l->p, up); dumpaproc(l->p); dumpaproc(up); } l->m = nil; coherence(); l->key = 0; if(up && --up->nlocks == 0 && up->delaysched && islo()){ /* * Call sched if the need arose while locks were held * But, don't do it from interrupt routines, hence the islo() test */ sched(); } } uintptr ilockpcs[0x100] = { [0xff] = 1 }; static int n; void iunlock(Lock *l) { ulong sr; #ifdef LOCKCYCLES l->lockcycles += lcycles(); cumilockcycles += l->lockcycles; if(l->lockcycles > maxilockcycles){ maxilockcycles = l->lockcycles; maxilockpc = l->pc; } if(l->lockcycles > 2400) ilockpcs[n++ & 0xff] = l->pc; #endif if(l->key == 0) print("iunlock(%#p): not locked: pc %#p\n", l, getcallerpc(&l)); if(!l->isilock) print("iunlock(%#p) of lock: pc %#p, held by %#p\n", l, getcallerpc(&l), l->pc); if(islo()) print("iunlock(%#p) while lo: pc %#p, held by %#p\n", l, getcallerpc(&l), l->pc); sr = l->sr; l->m = nil; coherence(); l->key = 0; m->ilockdepth--; if(up) up->lastilock = nil; splx(sr); }