[Qemu-devel] [PATCH v2 10/19] linux-user: Remove real-time signal queuing

[Peter Maydell <peter.maydell@linaro.org>]

From: Timothy E Baldwin <T.E.Baldwin99@members.leeds.ac.uk>

As host signals are now blocked whenever guest signals are blocked, the
queue of realtime signals is now in Linux. The QEMU queue is now
redundant and can be removed. (We already did not queue non-RT signals, and
none of the calls to queue_signal() except the one in host_signal_handler()
pass an RT signal number.)

Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
Message-id: 1441497448-32489-23-git-send-email-T.E.Baldwin99@members.leeds.ac.uk
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: minor commit message tweak]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 linux-user/main.c   |  7 ------
 linux-user/qemu.h   | 11 +--------
 linux-user/signal.c | 70 ++++++++++-------------------------------------------
 3 files changed, 14 insertions(+), 74 deletions(-)

diff --git a/linux-user/main.c b/linux-user/main.c
index b2bc6ab..b6da0ba 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -3794,14 +3794,7 @@ void stop_all_tasks(void)
 /* Assumes contents are already zeroed.  */
 void init_task_state(TaskState *ts)
 {
-    int i;
- 
     ts->used = 1;
-    ts->first_free = ts->sigqueue_table;
-    for (i = 0; i < MAX_SIGQUEUE_SIZE - 1; i++) {
-        ts->sigqueue_table[i].next = &ts->sigqueue_table[i + 1];
-    }
-    ts->sigqueue_table[i].next = NULL;
 }
 
 CPUArchState *cpu_copy(CPUArchState *env)
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 5138289..b201f90 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -78,16 +78,9 @@ struct vm86_saved_state {
 
 #define MAX_SIGQUEUE_SIZE 1024
 
-struct sigqueue {
-    struct sigqueue *next;
-    target_siginfo_t info;
-};
-
 struct emulated_sigtable {
     int pending; /* true if signal is pending */
-    struct sigqueue *first;
-    struct sigqueue info; /* in order to always have memory for the
-                             first signal, we put it here */
+    target_siginfo_t info;
 };
 
 /* NOTE: we force a big alignment so that the stack stored after is
@@ -127,8 +120,6 @@ typedef struct TaskState {
     struct linux_binprm *bprm;
 
     struct emulated_sigtable sigtab[TARGET_NSIG];
-    struct sigqueue sigqueue_table[MAX_SIGQUEUE_SIZE]; /* siginfo queue */
-    struct sigqueue *first_free; /* first free siginfo queue entry */
     /* This thread's signal mask, as requested by the guest program.
      * The actual signal mask of this thread may differ:
      *  + we don't let SIGSEGV and SIGBUS be blocked while running guest code
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 2c6790d..5db1c0b 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -441,27 +441,6 @@ void signal_init(void)
     }
 }
 
-/* signal queue handling */
-
-static inline struct sigqueue *alloc_sigqueue(CPUArchState *env)
-{
-    CPUState *cpu = ENV_GET_CPU(env);
-    TaskState *ts = cpu->opaque;
-    struct sigqueue *q = ts->first_free;
-    if (!q)
-        return NULL;
-    ts->first_free = q->next;
-    return q;
-}
-
-static inline void free_sigqueue(CPUArchState *env, struct sigqueue *q)
-{
-    CPUState *cpu = ENV_GET_CPU(env);
-    TaskState *ts = cpu->opaque;
-
-    q->next = ts->first_free;
-    ts->first_free = q;
-}
 
 /* abort execution with signal */
 static void QEMU_NORETURN force_sig(int target_sig)
@@ -524,37 +503,20 @@ int queue_signal(CPUArchState *env, int sig, target_siginfo_t *info)
     CPUState *cpu = ENV_GET_CPU(env);
     TaskState *ts = cpu->opaque;
     struct emulated_sigtable *k;
-    struct sigqueue *q, **pq;
 
     trace_user_queue_signal(env, sig);
     k = &ts->sigtab[sig - 1];
 
-        pq = &k->first;
-        if (sig < TARGET_SIGRTMIN) {
-            /* if non real time signal, we queue exactly one signal */
-            if (!k->pending)
-                q = &k->info;
-            else
-                return 0;
-        } else {
-            if (!k->pending) {
-                /* first signal */
-                q = &k->info;
-            } else {
-                q = alloc_sigqueue(env);
-                if (!q)
-                    return -EAGAIN;
-                while (*pq != NULL)
-                    pq = &(*pq)->next;
-            }
-        }
-        *pq = q;
-        q->info = *info;
-        q->next = NULL;
-        k->pending = 1;
-        /* signal that a new signal is pending */
-        atomic_set(&ts->signal_pending, 1);
-        return 1; /* indicates that the signal was queued */
+    /* we queue exactly one signal */
+    if (k->pending) {
+        return 0;
+    }
+
+    k->info = *info;
+    k->pending = 1;
+    /* signal that a new signal is pending */
+    atomic_set(&ts->signal_pending, 1);
+    return 1; /* indicates that the signal was queued */
 }
 
 #ifndef HAVE_SAFE_SYSCALL
@@ -5783,16 +5745,12 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig)
     sigset_t set;
     target_sigset_t target_old_set;
     struct target_sigaction *sa;
-    struct sigqueue *q;
     TaskState *ts = cpu->opaque;
     struct emulated_sigtable *k = &ts->sigtab[sig - 1];
 
     trace_user_handle_signal(cpu_env, sig);
     /* dequeue signal */
-    q = k->first;
-    k->first = q->next;
-    if (!k->first)
-        k->pending = 0;
+    k->pending = 0;
 
     sig = gdb_handlesig(cpu, sig);
     if (!sig) {
@@ -5857,10 +5815,10 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig)
 #if defined(TARGET_ABI_MIPSN32) || defined(TARGET_ABI_MIPSN64) \
     || defined(TARGET_OPENRISC) || defined(TARGET_TILEGX)
         /* These targets do not have traditional signals.  */
-        setup_rt_frame(sig, sa, &q->info, &target_old_set, cpu_env);
+        setup_rt_frame(sig, sa, &k->info, &target_old_set, cpu_env);
 #else
         if (sa->sa_flags & TARGET_SA_SIGINFO)
-            setup_rt_frame(sig, sa, &q->info, &target_old_set, cpu_env);
+            setup_rt_frame(sig, sa, &k->info, &target_old_set, cpu_env);
         else
             setup_frame(sig, sa, &target_old_set, cpu_env);
 #endif
@@ -5868,8 +5826,6 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig)
             sa->_sa_handler = TARGET_SIG_DFL;
         }
     }
-    if (q != &k->info)
-        free_sigqueue(cpu_env, q);
 }
 
 void process_pending_signals(CPUArchState *cpu_env)
-- 
1.9.1