diff options
| -rw-r--r-- | contrib/pg_buffercache/pg_buffercache_pages.c | 23 |
1 files changed, 4 insertions, 19 deletions
diff --git a/contrib/pg_buffercache/pg_buffercache_pages.c b/contrib/pg_buffercache/pg_buffercache_pages.c index da13bde3595..8bebf2384df 100644 --- a/contrib/pg_buffercache/pg_buffercache_pages.c +++ b/contrib/pg_buffercache/pg_buffercache_pages.c @@ -136,17 +136,12 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) MemoryContextSwitchTo(oldcontext); /* - * To get a consistent picture of the buffer state, we must lock all - * partitions of the buffer map. Needless to say, this is horrible - * for concurrency. Must grab locks in increasing order to avoid - * possible deadlocks. - */ - for (i = 0; i < NUM_BUFFER_PARTITIONS; i++) - LWLockAcquire(BufMappingPartitionLockByIndex(i), LW_SHARED); - - /* * Scan through all the buffers, saving the relevant fields in the * fctx->record structure. + * + * We don't hold the partition locks, so we don't get a consistent + * snapshot across all buffers, but we do grab the buffer header + * locks, so the information of each buffer is self-consistent. */ for (i = 0; i < NBuffers; i++) { @@ -179,16 +174,6 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) UnlockBufHdr(bufHdr, buf_state); } - - /* - * And release locks. We do this in reverse order for two reasons: - * (1) Anyone else who needs more than one of the locks will be trying - * to lock them in increasing order; we don't want to release the - * other process until it can get all the locks it needs. (2) This - * avoids O(N^2) behavior inside LWLockRelease. - */ - for (i = NUM_BUFFER_PARTITIONS; --i >= 0;) - LWLockRelease(BufMappingPartitionLockByIndex(i)); } funcctx = SRF_PERCALL_SETUP(); |