minix/kernel/system/do_exec.c
Tomas Hruby cbc9586c13 Lazy FPU
- FPU context is stored only if conflict between 2 FPU users or while
  exporting context of a process to userspace while it is the active
  user of FPU

- FPU has its owner (fpu_owner) which points to the process whose
  state is currently loaded in FPU

- the FPU exception is only turned on when scheduling a process which
  is not the owner of FPU

- FPU state is restored for the process that generated the FPU
  exception. This process runs immediately without letting scheduler
  to pick a new process to resolve the FPU conflict asap, to minimize
  the FPU thrashing and FPU exception hadler execution

- faster all non-FPU-exception kernel entries as FPU state is not
  checked nor saved

- removed MF_USED_FPU flag, only MF_FPU_INITIALIZED remains to signal
  that a process has used FPU in the past
2010-06-07 07:43:17 +00:00

55 lines
1.7 KiB
C

/* The kernel call implemented in this file:
* m_type: SYS_EXEC
*
* The parameters for this kernel call are:
* m1_i1: PR_ENDPT (process that did exec call)
* m1_p1: PR_STACK_PTR (new stack pointer)
* m1_p2: PR_NAME_PTR (pointer to program name)
* m1_p3: PR_IP_PTR (new instruction pointer)
*/
#include "kernel/system.h"
#include <string.h>
#include <minix/endpoint.h>
#if USE_EXEC
/*===========================================================================*
* do_exec *
*===========================================================================*/
PUBLIC int do_exec(struct proc * caller, message * m_ptr)
{
/* Handle sys_exec(). A process has done a successful EXEC. Patch it up. */
register struct proc *rp;
int proc_nr;
if(!isokendpt(m_ptr->PR_ENDPT, &proc_nr))
return EINVAL;
rp = proc_addr(proc_nr);
if(rp->p_misc_flags & MF_DELIVERMSG) {
rp->p_misc_flags &= ~MF_DELIVERMSG;
rp->p_delivermsg_lin = 0;
}
/* Save command name for debugging, ps(1) output, etc. */
if(data_copy(caller->p_endpoint, (vir_bytes) m_ptr->PR_NAME_PTR,
KERNEL, (vir_bytes) rp->p_name, (phys_bytes) P_NAME_LEN - 1) != OK)
strncpy(rp->p_name, "<unset>", P_NAME_LEN);
/* Do architecture-specific exec() stuff. */
arch_pre_exec(rp, (u32_t) m_ptr->PR_IP_PTR, (u32_t) m_ptr->PR_STACK_PTR);
/* No reply to EXEC call */
RTS_UNSET(rp, RTS_RECEIVING);
/* Mark fpu_regs contents as not significant, so fpu
* will be initialized, when it's used next time. */
rp->p_misc_flags &= ~MF_FPU_INITIALIZED;
/* force reloading FPU if the current process is the owner */
if (rp == fpu_owner)
release_fpu();
return(OK);
}
#endif /* USE_EXEC */