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Commit c5e3acd6 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
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s390/smp: avoid concurrent write to sigp status field 



When a sigp instruction is issued it may store a status. This status is
currently stored in a per cpu field of the target cpu.
If multiple cpus issue a sigp instruction with the same target cpu
and a status is stored the result is not necessarily as expected.

Currently this is not an issue:
- on cpu hotplug no sigps, except "restart" and "sense" are sent to the
  target cpu.
- on external call we don't look at the status if it is stored
- on sense running the condition code "status stored" is sufficient to
  tell if a cpu is running or not

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent fbf3c542

arch/s390/kernel/smp.c

+7 −6
Original line number Original line Diff line number Diff line
@@ -66,7 +66,6 @@ struct pcpu { 
	unsigned long panic_stack;	/* panic stack for the cpu */

	unsigned long panic_stack;	/* panic stack for the cpu */

	unsigned long ec_mask;		/* bit mask for ec_xxx functions */

	unsigned long ec_mask;		/* bit mask for ec_xxx functions */

	int state;			/* physical cpu state */

	int state;			/* physical cpu state */

	u32 status;			/* last status received via sigp */

	u16 address;			/* physical cpu address */

	u16 address;			/* physical cpu address */

};

};
@@ -99,7 +98,7 @@ static inline int __pcpu_sigp_relax(u16 addr, u8 order, u32 parm, u32 *status) 
	int cc;

	int cc;





	while (1) {

	while (1) {

		cc = __pcpu_sigp(addr, order, parm, status);

		cc = __pcpu_sigp(addr, order, parm, NULL);

		if (cc != SIGP_CC_BUSY)

		if (cc != SIGP_CC_BUSY)

			return cc;

			return cc;

		cpu_relax();

		cpu_relax();
@@ -111,7 +110,7 @@ static int pcpu_sigp_retry(struct pcpu *pcpu, u8 order, u32 parm) 
	int cc, retry;

	int cc, retry;





	for (retry = 0; ; retry++) {

	for (retry = 0; ; retry++) {

		cc = __pcpu_sigp(pcpu->address, order, parm, &pcpu->status);

		cc = __pcpu_sigp(pcpu->address, order, parm, NULL);

		if (cc != SIGP_CC_BUSY)

		if (cc != SIGP_CC_BUSY)

			break;

			break;

		if (retry >= 3)

		if (retry >= 3)
@@ -122,16 +121,18 @@ static int pcpu_sigp_retry(struct pcpu *pcpu, u8 order, u32 parm) 




static inline int pcpu_stopped(struct pcpu *pcpu)

static inline int pcpu_stopped(struct pcpu *pcpu)

{

{

	u32 status;



	if (__pcpu_sigp(pcpu->address, SIGP_SENSE,

	if (__pcpu_sigp(pcpu->address, SIGP_SENSE,

			0, &pcpu->status) != SIGP_CC_STATUS_STORED)

			0, &status) != SIGP_CC_STATUS_STORED)

		return 0;

		return 0;

	return !!(pcpu->status & (SIGP_STATUS_CHECK_STOP|SIGP_STATUS_STOPPED));

	return !!(status & (SIGP_STATUS_CHECK_STOP|SIGP_STATUS_STOPPED));

}

}





static inline int pcpu_running(struct pcpu *pcpu)

static inline int pcpu_running(struct pcpu *pcpu)

{

{

	if (__pcpu_sigp(pcpu->address, SIGP_SENSE_RUNNING,

	if (__pcpu_sigp(pcpu->address, SIGP_SENSE_RUNNING,

			0, &pcpu->status) != SIGP_CC_STATUS_STORED)

			0, NULL) != SIGP_CC_STATUS_STORED)

		return 1;

		return 1;

	/* Status stored condition code is equivalent to cpu not running. */

	/* Status stored condition code is equivalent to cpu not running. */

	return 0;

	return 0;