database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-11-26 23:43:30 +03:00
Code Activity

Don't be so trusting that shm_toc_lookup() will always succeed.

Browse Source 
Given the possibility of race conditions and so on, it seems entirely
unsafe to just assume that shm_toc_lookup() always finds the key it's
looking for --- but that was exactly what all but one call site were
doing.  To fix, add a "bool noError" argument, similarly to what we
have in many other functions, and throw an error on an unexpected
lookup failure.  Remove now-redundant Asserts that a rather random
subset of call sites had.

I doubt this will throw any light on buildfarm member lorikeet's
recent failures, because if an unnoticed lookup failure were involved,
you'd kind of expect a null-pointer-dereference crash rather than the
observed symptom.  But you never know ... and this is better coding
practice even if it never catches anything.

Discussion: https://postgr.es/m/9697.1496675981@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2017-06-05 12:05:42 -04:00
parent af51fea039
commit d466335064
11 changed files with 39 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
src/include/storage/shm_toc.h
View File

@@ -32,7 +32,7 @@ extern shm_toc *shm_toc_attach(uint64 magic, void *address);
extern void *shm_toc_allocate(shm_toc *toc, Size nbytes);
extern Size shm_toc_freespace(shm_toc *toc);
extern void shm_toc_insert(shm_toc *toc, uint64 key, void *address);
extern void *shm_toc_lookup(shm_toc *toc, uint64 key);
extern void *shm_toc_lookup(shm_toc *toc, uint64 key, bool noError);
/*
* Tools for estimating how large a chunk of shared memory will be needed