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authorAl Viro <viro@zeniv.linux.org.uk>2010-09-18 08:42:27 -0400
committerMatt Turner <mattst88@gmail.com>2010-09-18 23:08:29 -0400
commit494486a1d2697f2153199b6501ab5b4d6e15a2bb (patch)
tree8b4b00dcda14b47828a9c04a535550b8d545a0c0 /arch
parent53293638618f1a8b0b182dfedaab08b28930f992 (diff)
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alpha: deal with multiple simultaneously pending signals
Unlike the other targets, alpha sets _one_ sigframe and buggers off until the next syscall/interrupt, even if more signals are pending. It leads to quite a few unpleasant inconsistencies, starting with SIGSEGV potentially arriving not where it should and including e.g. mess with sigsuspend(); consider two pending signals blocked until sigsuspend() unblocks them. We pick the first one; then, if we are hit by interrupt while in the handler, we process the second one as well. If we are not, and if no syscalls had been made, we get out of the first handler and leave the second signal pending; normally sigreturn() would've picked it anyway, but here it starts with restoring the original mask and voila - the second signal is blocked again. On everything else we get both delivered consistently. It's actually easy to fix; the only thing to watch out for is prevention of double syscall restart. Fortunately, the idea I've nicked from arm fix by rmk works just fine... Testcase demonstrating the behaviour in question; on alpha we get one or both flags set (usually one), on everything else both are always set. #include <signal.h> #include <stdio.h> int had1, had2; void f1(int sig) { had1 = 1; } void f2(int sig) { had2 = 1; } main() { sigset_t set1, set2; sigemptyset(&set1); sigemptyset(&set2); sigaddset(&set2, 1); sigaddset(&set2, 2); signal(1, f1); signal(2, f2); sigprocmask(SIG_SETMASK, &set2, NULL); raise(1); raise(2); sigsuspend(&set1); printf("had1:%d had2:%d\n", had1, had2); } Tested-by: Michael Cree <mcree@orcon.net.nz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Matt Turner <mattst88@gmail.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/alpha/kernel/entry.S16
1 files changed, 11 insertions, 5 deletions
diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S
index a3e9cd85cfe..ab1ee0ab082 100644
--- a/arch/alpha/kernel/entry.S
+++ b/arch/alpha/kernel/entry.S
@@ -317,14 +317,14 @@ ret_from_sys_call:
ldq $0, SP_OFF($sp)
and $0, 8, $0
beq $0, restore_all
-ret_from_reschedule:
+ret_to_user:
/* Make sure need_resched and sigpending don't change between
sampling and the rti. */
lda $16, 7
call_pal PAL_swpipl
ldl $5, TI_FLAGS($8)
and $5, _TIF_WORK_MASK, $2
- bne $5, work_pending
+ bne $2, work_pending
restore_all:
RESTORE_ALL
call_pal PAL_rti
@@ -363,7 +363,7 @@ $ret_success:
* $8: current.
* $19: The old syscall number, or zero if this is not a return
* from a syscall that errored and is possibly restartable.
- * $20: Error indication.
+ * $20: The old a3 value
*/
.align 4
@@ -392,12 +392,18 @@ $work_resched:
$work_notifysig:
mov $sp, $16
- br $1, do_switch_stack
+ bsr $1, do_switch_stack
mov $sp, $17
mov $5, $18
+ mov $19, $9 /* save old syscall number */
+ mov $20, $10 /* save old a3 */
+ and $5, _TIF_SIGPENDING, $2
+ cmovne $2, 0, $9 /* we don't want double syscall restarts */
jsr $26, do_notify_resume
+ mov $9, $19
+ mov $10, $20
bsr $1, undo_switch_stack
- br restore_all
+ br ret_to_user
.end work_pending
/*