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| author | Siddhesh Poyarekar <siddhesh@redhat.com> | 2012-10-10 12:17:27 +0530 |
|---|---|---|
| committer | Siddhesh Poyarekar <siddhesh@redhat.com> | 2012-10-10 12:52:56 +0530 |
| commit | 0e3b5d6a6859d74a18033d3a55e0ee92340437b3 (patch) | |
| tree | b4f8c7fe139fb80e4fba77409942b68942a5df48 /nptl/sysdeps/unix | |
| parent | f96f12423a1b801f4a198f2568e29e85bd9cc473 (diff) | |
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Take lock in pthread_cond_wait cleanup handler only when needed
[BZ #14652]
When a thread waiting in pthread_cond_wait with a PI mutex is
cancelled after it has returned successfully from the futex syscall
but just before async cancellation is disabled, it enters its
cancellation handler with the mutex held and simply calling a
mutex_lock again will result in a deadlock. Hence, it is necessary to
see if the thread owns the lock and try to lock it only if it doesn't.
Diffstat (limited to 'nptl/sysdeps/unix')
5 files changed, 65 insertions, 8 deletions
diff --git a/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S b/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S index 6761c136e5..884987cf50 100644 --- a/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S +++ b/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S @@ -649,10 +649,24 @@ __condvar_tw_cleanup: movl $0x7fffffff, %edx ENTER_KERNEL + /* Lock the mutex only if we don't own it already. This only happens + in case of PI mutexes, if we got cancelled after a successful + return of the futex syscall and before disabling async + cancellation. */ 5: movl 24+FRAME_SIZE(%esp), %eax - call __pthread_mutex_cond_lock + movl MUTEX_KIND(%eax), %ebx + andl $(ROBUST_BIT|PI_BIT), %ebx + cmpl $PI_BIT, %ebx + jne 8f + + movl (%eax), %ebx + andl $TID_MASK, %ebx + cmpl %ebx, %gs:TID + je 9f + +8: call __pthread_mutex_cond_lock - movl %esi, (%esp) +9: movl %esi, (%esp) .LcallUR: call _Unwind_Resume hlt diff --git a/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S b/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S index 0af06acad4..bf1e5fe788 100644 --- a/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S +++ b/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S @@ -566,10 +566,24 @@ __condvar_w_cleanup: movl $0x7fffffff, %edx ENTER_KERNEL + /* Lock the mutex only if we don't own it already. This only happens + in case of PI mutexes, if we got cancelled after a successful + return of the futex syscall and before disabling async + cancellation. */ 5: movl 24+FRAME_SIZE(%esp), %eax - call __pthread_mutex_cond_lock + movl MUTEX_KIND(%eax), %ebx + andl $(ROBUST_BIT|PI_BIT), %ebx + cmpl $PI_BIT, %ebx + jne 8f + + movl (%eax), %ebx + andl $TID_MASK, %ebx + cmpl %ebx, %gs:TID + je 9f + +8: call __pthread_mutex_cond_lock - movl %esi, (%esp) +9: movl %esi, (%esp) .LcallUR: call _Unwind_Resume hlt diff --git a/nptl/sysdeps/unix/sysv/linux/pthread-pi-defines.sym b/nptl/sysdeps/unix/sysv/linux/pthread-pi-defines.sym index 46fbd0de74..0ac51dba98 100644 --- a/nptl/sysdeps/unix/sysv/linux/pthread-pi-defines.sym +++ b/nptl/sysdeps/unix/sysv/linux/pthread-pi-defines.sym @@ -6,3 +6,4 @@ MUTEX_KIND offsetof (pthread_mutex_t, __data.__kind) ROBUST_BIT PTHREAD_MUTEX_ROBUST_NORMAL_NP PI_BIT PTHREAD_MUTEX_PRIO_INHERIT_NP PS_BIT PTHREAD_MUTEX_PSHARED_BIT +TID_MASK FUTEX_TID_MASK diff --git a/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S b/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S index b669abb573..eb133266c6 100644 --- a/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S +++ b/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S @@ -771,10 +771,24 @@ __condvar_cleanup2: movl $SYS_futex, %eax syscall + /* Lock the mutex only if we don't own it already. This only happens + in case of PI mutexes, if we got cancelled after a successful + return of the futex syscall and before disabling async + cancellation. */ 5: movq 16(%rsp), %rdi - callq __pthread_mutex_cond_lock + movl MUTEX_KIND(%rdi), %eax + andl $(ROBUST_BIT|PI_BIT), %eax + cmpl $PI_BIT, %eax + jne 7f + + movl (%rdi), %eax + andl $TID_MASK, %eax + cmpl %eax, %fs:TID + je 8f + +7: callq __pthread_mutex_cond_lock - movq 24(%rsp), %rdi +8: movq 24(%rsp), %rdi movq FRAME_SIZE(%rsp), %r15 movq FRAME_SIZE+8(%rsp), %r14 movq FRAME_SIZE+16(%rsp), %r13 diff --git a/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S b/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S index ec403cd9b8..6c6dc0e74d 100644 --- a/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S +++ b/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S @@ -495,10 +495,24 @@ __condvar_cleanup1: movl $SYS_futex, %eax syscall + /* Lock the mutex only if we don't own it already. This only happens + in case of PI mutexes, if we got cancelled after a successful + return of the futex syscall and before disabling async + cancellation. */ 5: movq 16(%rsp), %rdi - callq __pthread_mutex_cond_lock + movl MUTEX_KIND(%rdi), %eax + andl $(ROBUST_BIT|PI_BIT), %eax + cmpl $PI_BIT, %eax + jne 7f + + movl (%rdi), %eax + andl $TID_MASK, %eax + cmpl %eax, %fs:TID + je 8f + +7: callq __pthread_mutex_cond_lock - movq 24(%rsp), %rdi +8: movq 24(%rsp), %rdi .LcallUR: call _Unwind_Resume@PLT hlt |