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Set max_safe_fds whenever we create shared memory and semaphores.

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Formerly we skipped this in bootstrap/check mode and in single-user
mode.  That's bad in check mode because it may allow accepting a
value of max_connections that doesn't actually work: on platforms
where semaphores consume file descriptors, there may not be enough
free FDs left over to satisfy fd.c, causing postmaster start to
fail.  It's also not great in single-user mode, because fd.c will
operate with just the minimum allowable value of max_safe_fds,
resulting in excess file open/close overhead if anything moderately
complicated is done in single-user mode.  (There may be some penalty
for bootstrap mode too, though probably not much.)

Discussion: https://postgr.es/m/2081982.1734393311@sss.pgh.pa.us
This commit is contained in:
Tom Lane 2024-12-17 12:23:26 -05:00
parent c91963da13
commit 21fb39cb07
2 changed files with 16 additions and 0 deletions
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6
src/backend/bootstrap/bootstrap.c
View File

@ -334,6 +334,12 @@ BootstrapModeMain(int argc, char *argv[], bool check_only)
CreateSharedMemoryAndSemaphores();
/*
* Estimate number of openable files. This is essential too in --check
* mode, because on some platforms semaphores count as open files.
*/
set_max_safe_fds();
/*
* XXX: It might make sense to move this into its own function at some
* point. Right now it seems like it'd cause more code duplication than

10
src/backend/tcop/postgres.c
View File

@ -4099,8 +4099,18 @@ PostgresSingleUserMain(int argc, char *argv[],
*/
InitializeWalConsistencyChecking();
/*
* Create shared memory etc. (Nothing's really "shared" in single-user
* mode, but we must have these data structures anyway.)
*/
CreateSharedMemoryAndSemaphores();
/*
* Estimate number of openable files. This must happen after setting up
* semaphores, because on some platforms semaphores count as open files.
*/
set_max_safe_fds();
/*
* Remember stand-alone backend startup time,roughly at the same point
* during startup that postmaster does so.