Change in ...osmo-trx[master]: radioInterface: Atomically fetch and change underrun variable

[pespin]

pespin has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-trx/+/15524


Change subject: radioInterface: Atomically fetch and change underrun variable
......................................................................

radioInterface: Atomically fetch and change underrun variable

Otherwise, it could happen that underrun events are lost:
TxLower (isUnderrun):	RxLower (pullBuffer):
read(underrun)
			read(underrun)
			write(underrun, |val) [maybe underrun becomes TRUE]
write(underrun, false)

Similary, it could happen the other direction if atomic was only applied
to isUnderrun:
TxLower (isUnderrun):	RxLower (pullBuffer):
			read(underrun) -> true
read(underrun)-> true
write(underrun, false)
			write(underrun, true|val) where val=false

So in here isUnderrun would return true twice while it should only
return one.

Change-Id: I684e0a5d2a9583a161d5a6593559b3a9e7cd57e3
---
M Transceiver52M/radioInterface.cpp
M Transceiver52M/radioInterface.h
M Transceiver52M/radioInterfaceMulti.cpp
M Transceiver52M/radioInterfaceResamp.cpp
4 files changed, 10 insertions(+), 10 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-trx refs/changes/24/15524/1

diff --git a/Transceiver52M/radioInterface.cpp b/Transceiver52M/radioInterface.cpp
index 6e49a75..bfd6099 100644
--- a/Transceiver52M/radioInterface.cpp
+++ b/Transceiver52M/radioInterface.cpp
@@ -288,9 +288,9 @@
 
 bool RadioInterface::isUnderrun()
 {
-  bool retVal = underrun;
-  underrun = false;
-
+  bool retVal;
+  /* atomically get previous value of "underrun" and set the var to false */
+  retVal = __sync_fetch_and_and(&underrun, false);
   return retVal;
 }
 
@@ -340,7 +340,7 @@
 			segmentLen * 2);
   }
 
-  underrun |= local_underrun;
+  __sync_or_and_fetch(&underrun, local_underrun);
   readTimestamp += numRecv;
   return 0;
 }
@@ -366,7 +366,7 @@
                                  segmentLen,
                                  &local_underrun,
                                  writeTimestamp);
-  underrun |= local_underrun;
+  __sync_or_and_fetch(&underrun, local_underrun);
   writeTimestamp += numSent;
 
   return true;
diff --git a/Transceiver52M/radioInterface.h b/Transceiver52M/radioInterface.h
index 83e00b9..6f4deaa 100644
--- a/Transceiver52M/radioInterface.h
+++ b/Transceiver52M/radioInterface.h
@@ -48,7 +48,7 @@
   std::vector<short *> convertRecvBuffer;
   std::vector<short *> convertSendBuffer;
   std::vector<float> powerScaling;
-  bool underrun;			      ///< indicates writes to USRP are too slow
+  int underrun;			              ///< indicates writes to USRP are too slow
   bool overrun;				      ///< indicates reads from USRP are too slow
   TIMESTAMP writeTimestamp;		      ///< sample timestamp of next packet written to USRP
   TIMESTAMP readTimestamp;		      ///< sample timestamp of next packet read from USRP
diff --git a/Transceiver52M/radioInterfaceMulti.cpp b/Transceiver52M/radioInterfaceMulti.cpp
index 99f6231..8060e73 100644
--- a/Transceiver52M/radioInterfaceMulti.cpp
+++ b/Transceiver52M/radioInterfaceMulti.cpp
@@ -251,7 +251,7 @@
 	convert_short_float((float *) outerRecvBuffer->begin(),
 			    convertRecvBuffer[0], 2 * outerRecvBuffer->size());
 
-	underrun |= local_underrun;
+	__sync_or_and_fetch(&underrun, local_underrun);
 	readTimestamp += num;
 
 	channelizer->rotate((float *) outerRecvBuffer->begin(),
@@ -348,7 +348,7 @@
 		LOG(ALERT) << "Transmit error " << num;
 	}
 
-	underrun |= local_underrun;
+	__sync_or_and_fetch(&underrun, local_underrun);
 	writeTimestamp += num;
 
 	return true;
diff --git a/Transceiver52M/radioInterfaceResamp.cpp b/Transceiver52M/radioInterfaceResamp.cpp
index 864cdee..03551ee 100644
--- a/Transceiver52M/radioInterfaceResamp.cpp
+++ b/Transceiver52M/radioInterfaceResamp.cpp
@@ -184,7 +184,7 @@
 	convert_short_float((float *) outerRecvBuffer->begin(),
 			    convertRecvBuffer[0], 2 * resamp_outchunk);
 
-	underrun |= local_underrun;
+	__sync_or_and_fetch(&underrun, local_underrun);
 	readTimestamp += (TIMESTAMP) resamp_outchunk;
 
 	/* Write to the end of the inner receive buffer */
@@ -232,7 +232,7 @@
 		LOG(ALERT) << "Transmit error " << numSent;
 	}
 
-	underrun |= local_underrun;
+	__sync_or_and_fetch(&underrun, local_underrun);
 	writeTimestamp += resamp_outchunk;
 
 	return true;

-- 
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Gerrit-Project: osmo-trx
Gerrit-Branch: master
Gerrit-Change-Id: I684e0a5d2a9583a161d5a6593559b3a9e7cd57e3
Gerrit-Change-Number: 15524
Gerrit-PatchSet: 1
Gerrit-Owner: pespin <pespin at sysmocom.de>
Gerrit-MessageType: newchange
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