From c5e3acd666543544d402c83d24d44e487fb51f11 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Thu, 30 Aug 2012 14:24:42 +0200 Subject: [PATCH] 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: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/smp.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index 87be102..c88fe85 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -66,7 +66,6 @@ struct pcpu { unsigned long panic_stack; /* panic stack for the cpu */ unsigned long ec_mask; /* bit mask for ec_xxx functions */ int state; /* physical cpu state */ - u32 status; /* last status received via sigp */ 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; while (1) { - cc = __pcpu_sigp(addr, order, parm, status); + cc = __pcpu_sigp(addr, order, parm, NULL); if (cc != SIGP_CC_BUSY) return cc; cpu_relax(); @@ -111,7 +110,7 @@ static int pcpu_sigp_retry(struct pcpu *pcpu, u8 order, u32 parm) int cc, 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) break; 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) { + u32 status; + if (__pcpu_sigp(pcpu->address, SIGP_SENSE, - 0, &pcpu->status) != SIGP_CC_STATUS_STORED) + 0, &status) != SIGP_CC_STATUS_STORED) 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) { if (__pcpu_sigp(pcpu->address, SIGP_SENSE_RUNNING, - 0, &pcpu->status) != SIGP_CC_STATUS_STORED) + 0, NULL) != SIGP_CC_STATUS_STORED) return 1; /* Status stored condition code is equivalent to cpu not running. */ return 0; -- 2.7.4