[tip: timers/core] posix-timers: Cleanup comments about timer ID tracking

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     10338fd15894827fefc2bf28ed75c81ba1dbfceb
Gitweb:        https://git.kernel.org/tip/10338fd15894827fefc2bf28ed75c81ba1dbfceb
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Tue, 25 Apr 2023 20:49:01 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Mon, 05 Jun 2023 17:03:37 +02:00

posix-timers: Cleanup comments about timer ID tracking

Describe the hash table properly and remove the IDR leftover comments.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230425183313.038444551@xxxxxxxxxxxxx

---
 kernel/time/posix-timers.c | 28 ++++++++--------------------
 1 file changed, 8 insertions(+), 20 deletions(-)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 4017533..355c6f4 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -35,20 +35,17 @@
 #include "timekeeping.h"
 #include "posix-timers.h"
 
-/*
- * Management arrays for POSIX timers. Timers are now kept in static hash table
- * with 512 entries.
- * Timer ids are allocated by local routine, which selects proper hash head by
- * key, constructed from current->signal address and per signal struct counter.
- * This keeps timer ids unique per process, but now they can intersect between
- * processes.
- */
+static struct kmem_cache *posix_timers_cache;
 
 /*
- * Lets keep our timers in a slab cache :-)
+ * Timers are managed in a hash table for lockless lookup. The hash key is
+ * constructed from current::signal and the timer ID and the timer is
+ * matched against current::signal and the timer ID when walking the hash
+ * bucket list.
+ *
+ * This allows checkpoint/restore to reconstruct the exact timer IDs for
+ * a process.
  */
-static struct kmem_cache *posix_timers_cache;
-
 static DEFINE_HASHTABLE(posix_timers_hashtable, 9);
 static DEFINE_SPINLOCK(hash_lock);
 
@@ -66,15 +63,6 @@ static const struct k_clock clock_realtime, clock_monotonic;
 #endif
 
 /*
- * The timer ID is turned into a timer address by idr_find().
- * Verifying a valid ID consists of:
- *
- * a) checking that idr_find() returns other than -1.
- * b) checking that the timer id matches the one in the timer itself.
- * c) that the timer owner is in the callers thread group.
- */
-
-/*
  * CLOCKs: The POSIX standard calls for a couple of clocks and allows us
  *	    to implement others.  This structure defines the various
  *	    clocks.