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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/alpha
parent53293638618f1a8b0b182dfedaab08b28930f992 (diff)
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/alpha')
-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 a3e9cd85cfee..ab1ee0ab082b 100644
--- a/arch/alpha/kernel/entry.S
+++ b/arch/alpha/kernel/entry.S
@@ -317,14 +317,14 @@ ret_from_sys_call:
317 ldq $0, SP_OFF($sp) 317 ldq $0, SP_OFF($sp)
318 and $0, 8, $0 318 and $0, 8, $0
319 beq $0, restore_all 319 beq $0, restore_all
320ret_from_reschedule: 320ret_to_user:
321 /* Make sure need_resched and sigpending don't change between 321 /* Make sure need_resched and sigpending don't change between
322 sampling and the rti. */ 322 sampling and the rti. */
323 lda $16, 7 323 lda $16, 7
324 call_pal PAL_swpipl 324 call_pal PAL_swpipl
325 ldl $5, TI_FLAGS($8) 325 ldl $5, TI_FLAGS($8)
326 and $5, _TIF_WORK_MASK, $2 326 and $5, _TIF_WORK_MASK, $2
327 bne $5, work_pending 327 bne $2, work_pending
328restore_all: 328restore_all:
329 RESTORE_ALL 329 RESTORE_ALL
330 call_pal PAL_rti 330 call_pal PAL_rti
@@ -363,7 +363,7 @@ $ret_success:
363 * $8: current. 363 * $8: current.
364 * $19: The old syscall number, or zero if this is not a return 364 * $19: The old syscall number, or zero if this is not a return
365 * from a syscall that errored and is possibly restartable. 365 * from a syscall that errored and is possibly restartable.
366 * $20: Error indication. 366 * $20: The old a3 value
367 */ 367 */
368 368
369 .align 4 369 .align 4
@@ -392,12 +392,18 @@ $work_resched:
392 392
393$work_notifysig: 393$work_notifysig:
394 mov $sp, $16 394 mov $sp, $16
395 br $1, do_switch_stack 395 bsr $1, do_switch_stack
396 mov $sp, $17 396 mov $sp, $17
397 mov $5, $18 397 mov $5, $18
398 mov $19, $9 /* save old syscall number */
399 mov $20, $10 /* save old a3 */
400 and $5, _TIF_SIGPENDING, $2
401 cmovne $2, 0, $9 /* we don't want double syscall restarts */
398 jsr $26, do_notify_resume 402 jsr $26, do_notify_resume
403 mov $9, $19
404 mov $10, $20
399 bsr $1, undo_switch_stack 405 bsr $1, undo_switch_stack
400 br restore_all 406 br ret_to_user
401.end work_pending 407.end work_pending
402 408
403/* 409/*