sys/src/spinlocks.c

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#include<linux/kernel.h>
#include<linux/sched.h>
#include<spldef.h>
#include<asm/bitops.h>
#include<system_data_cells.h>

/**
   \file spinlocks.c
   \brief spinlocking
   \author Roar Thronæs
*/

// define SPINDEF in spinlocks_mon?
#undef SPINDEB
#define SPINDEB

#ifdef SPINDEB
static int spinc = 0;
long spin[1024];
#endif

/**
   \brief acquire spinlock - see 5.2 8.3.8
   \param lockname
   \param lockipl -1 if no change
   \details not 100% according to spec
*/

inline int smp_acquire(struct _spl * spl) {
  /** remember to do a smp enabled check - MISSING */
#ifdef SPINDEB
  long * l = &spl;
  spin[spinc++]=l[-1];
  spin[spinc++]=spl;
  spin[spinc++]=ctl_gl_pcb;
  spin[spinc++]=l;
  spin[spinc++]=smp_processor_id();
  spin[spinc++]=spl->spl_l_own_cnt;
  spin[spinc++]=ctl_gl_pcb->psl_ipl;
  spin[spinc++]=0;
  if(spinc>1000) spinc=0;
#endif
  /** according to spec, this is really acquirel */
  /** ipl is raised before we call this, not accordig to spec */
  /** get cpu id */
 again:
  {}
  /** bbssi equivalent, set the spinlock bit */
  int bit = test_and_set_bit(0,&spl->spl_l_spinlock);
  if (bit) {
    /** if the bit was set, the spinlock has already been acquired */
    /** compare owner cpu with the cpu id (in spec addr) */
    if (spl->spl_l_own_cpu==smp$gl_cpu_data[ctl$gl_pcb->pcb$l_cpu_id]) {
      /** if equal, nested acquiring, increase own_cnt */
      spl->spl_l_own_cnt++;
    } else {
      /** if not loop in lock */
      while (test_bit(0,&spl->spl_l_spinlock)) {
      }
      goto again;
    }
  } else {
    /** if the bit was clear, this cpu now owns the lock */
    /** store cpu db id (speced address) in spinlock */
    spl->spl_l_own_cpu=smp$gl_cpu_data[ctl$gl_pcb->pcb$l_cpu_id];
#ifdef SPINDEB
    if (spl->spl_l_own_cpu==0)
      panic("cpu 0\n");
#endif
    /** increment spl own_cnt */
    spl->spl_l_own_cnt++;
#ifdef SPINDEB
    if (spl->spl_l_own_cnt==1) {
      panic("cnt 1\n");
#endif
    }
#if 0
    // check where the book wanted these
    int intr;
    local_irq_save(intr);
    local_irq_disable();
    local_irq_restore(intr);
#endif
  }
  /** use cpu busywait field - MISSING */
  /** use spl timo_int - MISSING */
}

/**
   \brief release spinlock - see 5.2 8.3.8
   \param lockname
   \param lockipl -1 if no change
   \details not 100% according to spec
*/

inline int smp_restore(struct _spl * spl) {
  /** remember to do a smp enabled check - MISSING */
  /** decrease spinlock owner count */
  spl->spl_l_own_cnt--;
  /** if count is -1, it is now free */
  if (spl->spl_l_own_cnt==-1) {
    /** set owner cpu to 0 */
    spl->spl_l_own_cpu = 0;
    /** BBCCI equivalent, clear spinlock bit to free it */
    clear_bit(0,&spl->spl_l_spinlock);
    /** test for bugcheck - MISSING */
  }
}
 

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