mirror of
https://github.com/HeyPuter/gex.git
synced 2026-11-13 20:12:43 -10:00
velzie
d2d6dc7043
The fetch already worked; what did not was what apt does with it.
E: Dynamic MMap ran out of room. Please increase the size of
APT::Cache-Start. Current value: 28311552.
E: Problem with MergeList .../binary-arm64_Packages
Bookworm's arm64 index is 49 MB of Packages and 32 MB of Translation-en, and
apt builds its cache in one mapping that it grows as it parses. Started at
the default it reaches about 27 MB and gives up. The size is a decision, not
a defect, so it is a decision the image makes: `/etc/apt/apt.conf.d/99gex`
sets `APT::Cache-Start` to 128 MB, next to the other four lines that already
tell apt it is running somewhere unusual. With that in the rootfs and nothing
on the command line:
== apt-get update ==
Get:1 http://deb.debian.org/debian bookworm InRelease [151 kB]
Get:2 http://deb.debian.org/debian bookworm/main arm64 Packages [8689 kB]
Get:3 http://deb.debian.org/debian bookworm/main Translation-en [6107 kB]
Fetched 14.9 MB in 3min 39s
Reading package lists...
== apt exit 0 ==
-rw-r--r-- 49434864 deb.debian.org_debian_dists_bookworm_main_binary-arm64_Packages
-rw-r--r-- 32699363 deb.debian.org_debian_dists_bookworm_main_i18n_Translation-en
and `apt-cache show bash` answers out of it.
Threads as Workers, continued, and still not working. Four more things that
were one set of bytes for a whole process and have to be one per Worker:
which thread it is running, where it resumes, why it stopped, and whether it
meant to give the stack back -- the last of those is why a thread that handed
the stack back correctly was reported as having crashed inside the shim. A
thread also has to be *entered* on its own registers, which it was not: `run`
starts at the first thread's context, so four threads all entered at 0x1000,
re-executed whatever the main thread was in the middle of, and one of them
came out the other side having forked. And a Worker that owns one thread must
not switch: neither the scheduler nor the safepoint may hand it another
thread, however ready that thread looks.
Where it stands: four threads start in four Workers, run their own registers,
and then one branches to address zero out of a futex. What is left is the
same kind of thing again -- the kernel keeps "which context is running" in a
field, and a field is per process.
`tests/integration/programs/thread-parallel.c` is the small version of
`threads.c`: four threads that share nothing, so that when both fail it says
whether the mechanism is broken or only the contention is.
53 lines
1.6 KiB
C
53 lines
1.6 KiB
C
/* Threads that do not fight over anything.
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*
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* The smallest program that can tell whether a thread ran at all in a Worker
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* of its own: each one writes only its own slot, and the main thread joins
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* them and adds up. No mutex, no condition variable, one futex per join.
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*
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* `threads.c` next door is the hard version and shares a mutex twenty
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* thousand times per thread. When both fail, this one says whether the
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* mechanism is broken or only the contention is, and those are days apart.
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*/
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#include <pthread.h>
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#include <stdio.h>
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#define N 4
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#define ITERS 100000
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struct arg { int id; long sum; int tid_seen; };
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static __thread int mine;
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static void *worker(void *p) {
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struct arg *a = p;
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/* Thread-local storage, which is the one piece of per-thread state that
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is not registers: each thread must see only its own. */
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mine = a->id;
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for (int i = 0; i < ITERS; i++) a->sum += i;
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a->tid_seen = mine;
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return NULL;
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}
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int main(void) {
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pthread_t t[N];
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struct arg args[N];
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for (int i = 0; i < N; i++) {
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args[i] = (struct arg){.id = i + 1, .sum = 0, .tid_seen = -1};
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if (pthread_create(&t[i], NULL, worker, &args[i]) != 0) {
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printf("pthread_create failed\n");
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return 1;
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}
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}
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long total = 0;
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int tls_ok = 1;
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for (int i = 0; i < N; i++) {
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pthread_join(t[i], NULL);
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total += args[i].sum;
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if (args[i].tid_seen != i + 1) tls_ok = 0;
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}
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printf("sum %ld expected %ld\n", total, (long)N * ITERS * (ITERS - 1) / 2);
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printf("tls %s\n", tls_ok ? "ok" : "WRONG");
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printf("main tls %d\n", mine);
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printf("done\n");
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return 0;
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}
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