posix-timers: Move sequence logic into struct k_itimer

The posix timer signal handling uses siginfo::si_sys_private for handling
the sequence counter check. That indirection is not longer required and the
sequence count value at signal queueing time can be stored in struct
k_itimer itself.

This removes the requirement of treating siginfo::si_sys_private special as
it's now always zero as the kernel does not touch it anymore.

Suggested-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://lore.kernel.org/all/20241105064213.852619866@linutronix.de

diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 28c0a30e08532c2fc561a3133686bfaa4aa5295e..49a89614d90016431c056a3efb3d9dfff2f2725d 100644 (file)
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -162,6 +162,7 @@ static inline void posix_cputimers_init_work(void) { }
  * @it_overrun:                The overrun counter for pending signals
  * @it_overrun_last:   The overrun at the time of the last delivered signal
  * @it_signal_seq:     Sequence count to control signal delivery
+ * @it_sigqueue_seq:   The sequence count at the point where the signal was queued
  * @it_sigev_notify:   The notify word of sigevent struct for signal delivery
  * @it_interval:       The interval for periodic timers
  * @it_signal:         Pointer to the creators signal struct
@@ -184,6 +185,7 @@ struct k_itimer {
        s64                     it_overrun;
        s64                     it_overrun_last;
        unsigned int            it_signal_seq;
+       unsigned int            it_sigqueue_seq;
        int                     it_sigev_notify;
        enum pid_type           it_pid_type;
        ktime_t                 it_interval;

diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h
index b7bc545ec3b2ceaaf373224c884a8bdc27a6e834..5a1ca43b5fc60623d9c229f91447f83460bf77b1 100644 (file)
--- a/include/uapi/asm-generic/siginfo.h
+++ b/include/uapi/asm-generic/siginfo.h
@@ -46,7 +46,7 @@ union __sifields {
                __kernel_timer_t _tid;  /* timer id */
                int _overrun;           /* overrun count */
                sigval_t _sigval;       /* same as below */
-               int _sys_private;       /* not to be passed to user */
+               int _sys_private;       /* Not used by the kernel. Historic leftover. Always 0. */
        } _timer;
 
        /* POSIX.1b signals */

diff --git a/kernel/signal.c b/kernel/signal.c
index d267a2c5e9778509c02761436f55bb5974843803..d2734dc4d74ffd72bc563aa6b1d132c81996ba3f 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1976,12 +1976,10 @@ int posixtimer_send_sigqueue(struct k_itimer *tmr)
                return -1;
 
        /*
-        * Update @q::info::si_sys_private for posix timer signals with
-        * sighand locked to prevent a race against dequeue_signal() which
-        * decides based on si_sys_private whether to invoke
-        * posixtimer_rearm() or not.
+        * Update @tmr::sigqueue_seq for posix timer signals with sighand
+        * locked to prevent a race against dequeue_signal().
         */
-       q->info.si_sys_private = tmr->it_signal_seq;
+       tmr->it_sigqueue_seq = tmr->it_signal_seq;
 
        ret = 1; /* the signal is ignored */
        if (!prepare_signal(sig, t, false)) {

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 2e2c0edcfa97d5a6716a5f8acfb0131bd89b0f1e..f20c06d0cf09d0735ea99af1c5c38fd38377f5a6 100644 (file)
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -259,7 +259,7 @@ static bool __posixtimer_deliver_signal(struct kernel_siginfo *info, struct k_it
         * since the signal was queued. In either case, don't rearm and
         * drop the signal.
         */
-       if (timr->it_signal_seq != info->si_sys_private || WARN_ON_ONCE(!timr->it_signal))
+       if (timr->it_signal_seq != timr->it_sigqueue_seq || WARN_ON_ONCE(!timr->it_signal))
                return false;
 
        if (!timr->it_interval || WARN_ON_ONCE(timr->it_status != POSIX_TIMER_REQUEUE_PENDING))
@@ -297,9 +297,6 @@ bool posixtimer_deliver_signal(struct kernel_siginfo *info, struct sigqueue *tim
        posixtimer_putref(timr);
 
        spin_lock(&current->sighand->siglock);
-
-       /* Don't expose the si_sys_private value to userspace */
-       info->si_sys_private = 0;
        return ret;
 }