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charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: AE6A980006 X-Stat-Signature: ajgb6udinmbemw41qny6w51yfgnj71nh X-HE-Tag: 1681379094-674119 X-HE-Meta: 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 PJiHeTK8 +uxspBx7w2vimembYPUfgV/Anp2SyTW4fWMd5/EBYulze4em/JQYO16y5w5ccsPwT8lf21aSebe9jL+CaXnDym32M8eqDmwupArXa8XYxsvBCyoKdsxhcEds0c23l/gVlVvvmudn2OHB/vIzYeVEK0pW/3k9Edohmko4TD285qcb6KvxMOD3bW2BNBhgJzMpvcvaB+TKvvn+TLb+Ic9be6H2MilccdnJ3hak6HNWnsxwzo/TgxoyzKh6ac+Xdt7nznXZodfhVx7F6bG8liNvsxARZ58hOWzmFfsXFXVR3DJ8mRGXdo/WhK4sUDA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi, On Wed, 5 Apr 2023, Luis Chamberlain wrote: s/sempahore/semaphore/ in the subject > Simplfy the concurrency delimiter we user for kmod with the semaphore. "Simplify the concurrency delimiter we use for kmod with the semaphore." (two typos) > I had used the kmod strategy to try to implement a similar concurrency > delimiter for the kernel_read*() calls from the finit_module() path > so to reduce vmalloc() memory pressure. That effort didn't provid yet s/provid/provide/ > conclusive results, but one thing that did became clear is we can use s/did // (or s/became/become/) > the suggested alternative solution with semaphores which Linus hinted > at instead of using the atomic / wait strategy. > > I've stress tested this with kmod test 0008: > > time /data/linux-next/tools/testing/selftests/kmod/kmod.sh -t 0008 > > And I get only a *slight* delay. That delay however is small, a few > seconds for a full test loop run that runs 150 times, for about ~30-40 > seconds. The small delay is worth the simplfication IMHO. > > Signed-off-by: Luis Chamberlain > --- > kernel/module/kmod.c | 26 +++++++------------------- > 1 file changed, 7 insertions(+), 19 deletions(-) > > diff --git a/kernel/module/kmod.c b/kernel/module/kmod.c > index b717134ebe17..925eb85b8346 100644 > --- a/kernel/module/kmod.c > +++ b/kernel/module/kmod.c > @@ -40,8 +40,7 @@ > * effect. Systems like these are very unlikely if modules are enabled. > */ > #define MAX_KMOD_CONCURRENT 50 > -static atomic_t kmod_concurrent_max = ATOMIC_INIT(MAX_KMOD_CONCURRENT); > -static DECLARE_WAIT_QUEUE_HEAD(kmod_wq); > +static DEFINE_SEMAPHORE(kmod_concurrent_max, MAX_KMOD_CONCURRENT); > > /* > * This is a restriction on having *all* MAX_KMOD_CONCURRENT threads > @@ -148,29 +147,18 @@ int __request_module(bool wait, const char *fmt, ...) > if (ret) > return ret; > > - if (atomic_dec_if_positive(&kmod_concurrent_max) < 0) { > - pr_warn_ratelimited("request_module: kmod_concurrent_max (%u) close to 0 (max_modprobes: %u), for module %s, throttling...", > - atomic_read(&kmod_concurrent_max), > - MAX_KMOD_CONCURRENT, module_name); > - ret = wait_event_killable_timeout(kmod_wq, > - atomic_dec_if_positive(&kmod_concurrent_max) >= 0, > - MAX_KMOD_ALL_BUSY_TIMEOUT * HZ); > - if (!ret) { > - pr_warn_ratelimited("request_module: modprobe %s cannot be processed, kmod busy with %d threads for more than %d seconds now", > - module_name, MAX_KMOD_CONCURRENT, MAX_KMOD_ALL_BUSY_TIMEOUT); > - return -ETIME; > - } else if (ret == -ERESTARTSYS) { > - pr_warn_ratelimited("request_module: sigkill sent for modprobe %s, giving up", module_name); > - return ret; > - } > + ret = down_timeout(&kmod_concurrent_max, MAX_KMOD_ALL_BUSY_TIMEOUT); MAX_KMOD_ALL_BUSY_TIMEOUT * HZ ? The simplification is very nice. Miroslav