[PATCH] m32r: update sys_tas() routine
This patch updates and fixes sys_tas() routine for m32r. In the previous implementation, a lockup rarely caused at sys_tas() routine in SMP environment. > > The problem is that touching *addr will generate an oops if that page isn't > > paged in. If we convert it to use get_user() then that's an improvement, > > but we must not run get_user() under spinlock or local_irq_disable(). I rewrote sys_tas() routine by using "lock -> unlock" instructions, and utilizing the m32r's interrupt handling characteristics; the m32r processor can accept interrupts only at the 32-bit instruction boundary. So, the "unlock" instruction can be executed continuously after the "lock" instruction execution without any interruptions. In addition, to solve such a page_fault problem, I use a fixup code like get_user(). And, as for the kernel lockup problem, we found that a calling do_page_fault() routine with disabling interrupts might cause a lockup at flush_tlb_others(), because we checked a completion of IPI handler's operations in a spin-locked critical section. Therefore, by using "lock -> unlock" code, we can implement the sys_tas() rouitine without disabling interrupts explicitly, then no lockups would happen at flush_tlb_others(), I hope. Compile check and some working test in SMP environment have done. Signed-off-by: Hirokazu Takata <takata@linux-m32r.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
parent
b04ec261bd
commit
cf535ea52e
|
@ -29,28 +29,7 @@
|
|||
|
||||
/*
|
||||
* sys_tas() - test-and-set
|
||||
* linuxthreads testing version
|
||||
*/
|
||||
#ifndef CONFIG_SMP
|
||||
asmlinkage int sys_tas(int *addr)
|
||||
{
|
||||
int oldval;
|
||||
unsigned long flags;
|
||||
|
||||
if (!access_ok(VERIFY_WRITE, addr, sizeof (int)))
|
||||
return -EFAULT;
|
||||
local_irq_save(flags);
|
||||
oldval = *addr;
|
||||
if (!oldval)
|
||||
*addr = 1;
|
||||
local_irq_restore(flags);
|
||||
return oldval;
|
||||
}
|
||||
#else /* CONFIG_SMP */
|
||||
#include <linux/spinlock.h>
|
||||
|
||||
static DEFINE_SPINLOCK(tas_lock);
|
||||
|
||||
asmlinkage int sys_tas(int *addr)
|
||||
{
|
||||
int oldval;
|
||||
|
@ -58,15 +37,43 @@ asmlinkage int sys_tas(int *addr)
|
|||
if (!access_ok(VERIFY_WRITE, addr, sizeof (int)))
|
||||
return -EFAULT;
|
||||
|
||||
_raw_spin_lock(&tas_lock);
|
||||
oldval = *addr;
|
||||
if (!oldval)
|
||||
*addr = 1;
|
||||
_raw_spin_unlock(&tas_lock);
|
||||
/* atomic operation:
|
||||
* oldval = *addr; *addr = 1;
|
||||
*/
|
||||
__asm__ __volatile__ (
|
||||
DCACHE_CLEAR("%0", "r4", "%1")
|
||||
" .fillinsn\n"
|
||||
"1:\n"
|
||||
" lock %0, @%1 -> unlock %2, @%1\n"
|
||||
"2:\n"
|
||||
/* NOTE:
|
||||
* The m32r processor can accept interrupts only
|
||||
* at the 32-bit instruction boundary.
|
||||
* So, in the above code, the "unlock" instruction
|
||||
* can be executed continuously after the "lock"
|
||||
* instruction execution without any interruptions.
|
||||
*/
|
||||
".section .fixup,\"ax\"\n"
|
||||
" .balign 4\n"
|
||||
"3: ldi %0, #%3\n"
|
||||
" seth r14, #high(2b)\n"
|
||||
" or3 r14, r14, #low(2b)\n"
|
||||
" jmp r14\n"
|
||||
".previous\n"
|
||||
".section __ex_table,\"a\"\n"
|
||||
" .balign 4\n"
|
||||
" .long 1b,3b\n"
|
||||
".previous\n"
|
||||
: "=&r" (oldval)
|
||||
: "r" (addr), "r" (1), "i"(-EFAULT)
|
||||
: "r14", "memory"
|
||||
#ifdef CONFIG_CHIP_M32700_TS1
|
||||
, "r4"
|
||||
#endif /* CONFIG_CHIP_M32700_TS1 */
|
||||
);
|
||||
|
||||
return oldval;
|
||||
}
|
||||
#endif /* CONFIG_SMP */
|
||||
|
||||
/*
|
||||
* sys_pipe() is the normal C calling standard for creating
|
||||
|
|
Loading…
Reference in a new issue