* + kernel-asyncc-stop-guarding-pr_debug-statements.patch added to -mm tree
@ 2021-03-11 22:23 akpm
0 siblings, 0 replies; only message in thread
From: akpm @ 2021-03-11 22:23 UTC (permalink / raw)
To: linux, mm-commits, tj
The patch titled
Subject: kernel/async.c: stop guarding pr_debug() statements
has been added to the -mm tree. Its filename is
kernel-asyncc-stop-guarding-pr_debug-statements.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kernel-asyncc-stop-guarding-pr_debug-statements.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kernel-asyncc-stop-guarding-pr_debug-statements.patch
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------------------------------------------------------
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: kernel/async.c: stop guarding pr_debug() statements
It's currently nigh impossible to get these pr_debug()s to print
something. Being guarded by initcall_debug means one has to enable tons
of other debug output during boot, and the system_state condition further
means it's impossible to get them when loading modules later.
Also, the compiler can't know that these global conditions do not change,
so there are W=2 warnings
kernel/async.c:125:9: warning: `calltime' may be used uninitialized in this function [-Wmaybe-uninitialized]
kernel/async.c:300:9: warning: `starttime' may be used uninitialized in this function [-Wmaybe-uninitialized]
Make it possible, for a DYNAMIC_DEBUG kernel, to get these to print their
messages by booting with appropriate 'dyndbg="file async.c +p"' command
line argument. For a non-DYNAMIC_DEBUG kernel, pr_debug() compiles to
nothing.
This does cost doing an unconditional ktime_get() for the starttime value,
but the corresponding ktime_get for the end time can be elided by
factoring it into a function which only gets called if the printk()
arguments end up being evaluated.
Link: https://lkml.kernel.org/r/20210309151723.1907838-1-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
kernel/async.c | 48 +++++++++++++++++++----------------------------
1 file changed, 20 insertions(+), 28 deletions(-)
--- a/kernel/async.c~kernel-asyncc-stop-guarding-pr_debug-statements
+++ a/kernel/async.c
@@ -78,6 +78,12 @@ static DECLARE_WAIT_QUEUE_HEAD(async_don
static atomic_t entry_count;
+static long long microseconds_since(ktime_t start)
+{
+ ktime_t now = ktime_get();
+ return ktime_to_ns(ktime_sub(now, start)) >> 10;
+}
+
static async_cookie_t lowest_in_progress(struct async_domain *domain)
{
struct async_entry *first = NULL;
@@ -111,24 +117,18 @@ static void async_run_entry_fn(struct wo
struct async_entry *entry =
container_of(work, struct async_entry, work);
unsigned long flags;
- ktime_t calltime, delta, rettime;
+ ktime_t calltime;
/* 1) run (and print duration) */
- if (initcall_debug && system_state < SYSTEM_RUNNING) {
- pr_debug("calling %lli_%pS @ %i\n",
- (long long)entry->cookie,
- entry->func, task_pid_nr(current));
- calltime = ktime_get();
- }
+ pr_debug("calling %lli_%pS @ %i\n", (long long)entry->cookie,
+ entry->func, task_pid_nr(current));
+ calltime = ktime_get();
+
entry->func(entry->data, entry->cookie);
- if (initcall_debug && system_state < SYSTEM_RUNNING) {
- rettime = ktime_get();
- delta = ktime_sub(rettime, calltime);
- pr_debug("initcall %lli_%pS returned after %lld usecs\n",
- (long long)entry->cookie,
- entry->func,
- (long long)ktime_to_ns(delta) >> 10);
- }
+
+ pr_debug("initcall %lli_%pS returned after %lld usecs\n",
+ (long long)entry->cookie, entry->func,
+ microseconds_since(calltime));
/* 2) remove self from the pending queues */
spin_lock_irqsave(&async_lock, flags);
@@ -287,23 +287,15 @@ EXPORT_SYMBOL_GPL(async_synchronize_full
*/
void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain)
{
- ktime_t starttime, delta, endtime;
+ ktime_t starttime;
- if (initcall_debug && system_state < SYSTEM_RUNNING) {
- pr_debug("async_waiting @ %i\n", task_pid_nr(current));
- starttime = ktime_get();
- }
+ pr_debug("async_waiting @ %i\n", task_pid_nr(current));
+ starttime = ktime_get();
wait_event(async_done, lowest_in_progress(domain) >= cookie);
- if (initcall_debug && system_state < SYSTEM_RUNNING) {
- endtime = ktime_get();
- delta = ktime_sub(endtime, starttime);
-
- pr_debug("async_continuing @ %i after %lli usec\n",
- task_pid_nr(current),
- (long long)ktime_to_ns(delta) >> 10);
- }
+ pr_debug("async_continuing @ %i after %lli usec\n", task_pid_nr(current),
+ microseconds_since(starttime));
}
EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
_
Patches currently in -mm which might be from linux@rasmusvillemoes.dk are
kernel-asyncc-fix-pr_debug-statement.patch
kernel-credc-make-init_groups-static.patch
kernel-asyncc-stop-guarding-pr_debug-statements.patch
kernel-asyncc-remove-async_unregister_domain.patch
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2021-03-11 22:23 + kernel-asyncc-stop-guarding-pr_debug-statements.patch added to -mm tree akpm
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