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Commit2a8a006

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Fix explicit valgrind interaction in read_stream.c.
By calling wipe_mem() on per-buffer data memory that has been released,we are also telling Valgrind that the memory is "noaccess". We need toset it to "undefined" before giving it to the registered callback tofill in, when a slot is reused.As discovered by build farm animal skink when the VACUUM streamificationpatches landed (the first users of per-buffer data).Pushing to master only for now, to clear the error on skink. It's alsopossible that external code might discover the per-buffer data featurein v17, and reasonable to expect Valgrind not to produce spuriousmemcheck reports, but the back-patch is deferred until after theimminent minor release is out of the way.Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>Tested-by: Melanie Plageman <melanieplageman@gmail.com>Discussion:https://postgr.es/m/CA%2BhUKG%2Bg6aXpi2FEHqeLOzE%2BxYw%3DOV%2B-N5jhOEnnV%2BF0USM9xA%40mail.gmail.com
1 parentefdadeb commit2a8a006

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1 file changed

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‎src/backend/storage/aio/read_stream.c

Lines changed: 32 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -193,9 +193,20 @@ read_stream_get_block(ReadStream *stream, void *per_buffer_data)
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if (blocknum!=InvalidBlockNumber)
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stream->buffered_blocknum=InvalidBlockNumber;
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else
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{
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/*
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* Tell Valgrind that the per-buffer data is undefined. That replaces
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* the "noaccess" state that was set when the consumer moved past this
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* entry last time around the queue, and should also catch callbacks
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* that fail to initialize data that the buffer consumer later
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* accesses. On the first go around, it is undefined already.
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*/
204+
VALGRIND_MAKE_MEM_UNDEFINED(per_buffer_data,
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stream->per_buffer_data_size);
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blocknum=stream->callback(stream,
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stream->callback_private_data,
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per_buffer_data);
209+
}
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200211
returnblocknum;
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}
@@ -752,8 +763,11 @@ read_stream_next_buffer(ReadStream *stream, void **per_buffer_data)
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}
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#ifdefCLOBBER_FREED_MEMORY
755-
/* Clobber old bufferand per-buffer datafor debugging purposes. */
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/* Clobber old buffer for debugging purposes. */
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stream->buffers[oldest_buffer_index]=InvalidBuffer;
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#endif
769+
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#if defined(CLOBBER_FREED_MEMORY)|| defined(USE_VALGRIND)
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/*
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* The caller will get access to the per-buffer data, until the next call.
@@ -762,11 +776,23 @@ read_stream_next_buffer(ReadStream *stream, void **per_buffer_data)
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* that is holding a dangling pointer to it.
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*/
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if (stream->per_buffer_data)
765-
wipe_mem(get_per_buffer_data(stream,
766-
oldest_buffer_index==0 ?
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stream->queue_size-1 :
768-
oldest_buffer_index-1),
769-
stream->per_buffer_data_size);
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{
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void*per_buffer_data;
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per_buffer_data=get_per_buffer_data(stream,
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oldest_buffer_index==0 ?
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stream->queue_size-1 :
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oldest_buffer_index-1);
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#if defined(CLOBBER_FREED_MEMORY)
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/* This also tells Valgrind the memory is "noaccess". */
789+
wipe_mem(per_buffer_data,stream->per_buffer_data_size);
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#elif defined(USE_VALGRIND)
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/* Tell it ourselves. */
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VALGRIND_MAKE_MEM_NO_ACCESS(per_buffer_data,
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stream->per_buffer_data_size);
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#endif
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}
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#endif
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/* Pin transferred to caller. */

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