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Fix SystemTap dtrace warning about smgr probe argument types.

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Commits ca326e903 and 1f8c504e3 widened the byte-count arguments of
smgr__md__read__done and smgr__md__write__done to "long long int".
SystemTap's dtrace(1) fails on that specific spelling and falls back
with a warning (misreported near the previous probe).  Use ssize_t
and size_t instead, matching the md.c call sites.

Revise probes.d's note about which types are usable as probe
arguments: recommend using system-supplied type names (macOS dtrace
rejects names like PostgreSQL's uint64), and call out "long long int"
as a known SystemTap failure case rather than a wider failure mode.

Also, update the monitoring.sgml entries for these probes,
which were missed by the prior commits.

Reported-by: Laurenz Albe <laurenz.albe@cybertec.at>
Author: Andrey Rachitskiy <pl0h0yp1@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/697d3c88568442cd637d8453d129f1bb14bbd2a8.camel@cybertec.at
This commit is contained in:
Tom Lane
2026-07-29 20:25:54 -04:00
parent b43e8f4b3d
commit 8f191a7961
2 changed files with 12 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
doc/src/sgml/monitoring.sgml
View File

@@ -8745,7 +8745,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
</row>
<row>
<entry><literal>smgr-md-read-done</literal></entry>
<entry><literal>(ForkNumber, BlockNumber, Oid, Oid, Oid, int, int, int)</literal></entry>
<entry><literal>(ForkNumber, BlockNumber, Oid, Oid, Oid, int, ssize_t, size_t)</literal></entry>
<entry>Probe that fires when a block read is complete.
arg0 and arg1 contain the fork and block numbers of the page.
arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
@@ -8767,7 +8767,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
</row>
<row>
<entry><literal>smgr-md-write-done</literal></entry>
<entry><literal>(ForkNumber, BlockNumber, Oid, Oid, Oid, int, int, int)</literal></entry>
<entry><literal>(ForkNumber, BlockNumber, Oid, Oid, Oid, int, ssize_t, size_t)</literal></entry>
<entry>Probe that fires when a block write is complete.
arg0 and arg1 contain the fork and block numbers of the page.
arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs

14
src/backend/utils/probes.d
View File

@@ -11,8 +11,14 @@
/*
* Typedefs used in PostgreSQL probes.
*
* NOTE: Do not use system-provided typedefs (e.g. uintptr_t, uint32_t, etc)
* in probe definitions, as they cause compilation errors on macOS.
* NOTE: Prefer system-supplied type names in probe definitions (e.g.
* uint64_t, not PostgreSQL's uint64); macOS' dtrace rejects the latter.
* Also avoid "long long int", as SystemTap's dtrace(1) fails on that
* specific spelling.
*
* But we can use some PG type aliases by #define'ing them here so that
* cpp expands them before dtrace sees the file. Curiously, macOS' dtrace
* rejects "bool", so we handle that with a #define too.
*/
#define LocalTransactionId unsigned int
#define LWLockMode int
@@ -83,9 +89,9 @@ provider postgresql {
probe twophase__checkpoint__done();
probe smgr__md__read__start(ForkNumber, BlockNumber, Oid, Oid, Oid, int);
probe smgr__md__read__done(ForkNumber, BlockNumber, Oid, Oid, Oid, int, long long int, long long int);
probe smgr__md__read__done(ForkNumber, BlockNumber, Oid, Oid, Oid, int, ssize_t, size_t);
probe smgr__md__write__start(ForkNumber, BlockNumber, Oid, Oid, Oid, int);
probe smgr__md__write__done(ForkNumber, BlockNumber, Oid, Oid, Oid, int, long long int, long long int);
probe smgr__md__write__done(ForkNumber, BlockNumber, Oid, Oid, Oid, int, ssize_t, size_t);
probe wal__insert(unsigned char, unsigned char);
probe wal__switch();