leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

kernel/async.c: stop guarding pr_debug() statements

Browse Source 
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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rasmus Villemoes 2021-05-06 18:05:36 -07:00 committed by Linus Torvalds
parent 9c39c6ffe0
commit 07416af11d
1 changed files with 20 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
kernel/async.c
View File

@ -78,6 +78,12 @@ static DECLARE_WAIT_QUEUE_HEAD(async_done);
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 work_struct *work)
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_domain);
*/
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);